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Posted to commits@helix.apache.org by jx...@apache.org on 2017/06/12 23:31:18 UTC
[1/3] helix git commit: Prepare website for 0.6.8 release and add
0.6.8 release notes.
Repository: helix
Updated Branches:
refs/heads/master 01f13c9ba -> 09a54c8eb
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_state.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - State Machine Configuration</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): State Machine Configuration
+
+In this chapter, we\'ll learn about the state models provided by Helix, and how to create your own custom state model.
+
+### State Models
+
+Helix comes with 3 default state models that are commonly used. It is possible to have multiple state models in a cluster.
+Every resource that is added should be configured to use a state model that govern its _ideal state_.
+
+#### MASTER-SLAVE
+
+* 3 states: OFFLINE, SLAVE, MASTER
+* Maximum number of masters: 1
+* Slaves are based on the replication factor. The replication factor can be specified while adding the resource.
+
+
+#### ONLINE-OFFLINE
+
+* Has 2 states: OFFLINE and ONLINE. This simple state model is a good starting point for most applications.
+
+#### LEADER-STANDBY
+
+* 1 Leader and multiple stand-bys. The idea is that exactly one leader accomplishes a designated task, the stand-bys are ready to take over if the leader fails.
+
+### Constraints
+
+In addition to the state machine configuration, one can specify the constraints of states and transitions.
+
+For example, one can say:
+
+* MASTER:1
+<br/>Maximum number of replicas in MASTER state at any time is 1
+
+* OFFLINE-SLAVE:5
+<br/>Maximum number of OFFLINE-SLAVE transitions that can happen concurrently in the system is 5 in this example.
+
+#### Dynamic State Constraints
+
+We also support two dynamic upper bounds for the number of replicas in each state:
+
+* N: The number of replicas in the state is at most the number of live participants in the cluster
+* R: The number of replicas in the state is at most the specified replica count for the partition
+
+#### State Priority
+
+Helix uses a greedy approach to satisfy the state constraints. For example, if the state machine configuration says it needs 1 MASTER and 2 SLAVES, but only 1 node is active, Helix must promote it to MASTER. This behavior is achieved by providing the state priority list as \[MASTER, SLAVE\].
+
+#### State Transition Priority
+
+Helix tries to fire as many transitions as possible in parallel to reach the stable state without violating constraints. By default, Helix simply sorts the transitions alphabetically and fires as many as it can without violating the constraints. You can control this by overriding the priority order.
+
+### Special States
+
+There are a few Helix-defined states that are important to be aware of.
+
+#### DROPPED
+
+The DROPPED state is used to signify a replica that was served by a given participant, but is no longer served. This allows Helix and its participants to effectively clean up. There are two requirements that every new state model should follow with respect to the DROPPED state:
+
+* The DROPPED state must be defined
+* There must be a path to DROPPED for every state in the model
+
+#### ERROR
+
+The ERROR state is used whenever the participant serving a partition encountered an error and cannot continue to serve the partition. HelixAdmin has \"reset\" functionality to allow for participants to recover from the ERROR state.
+
+### Annotated Example
+
+Below is a complete definition of a Master-Slave state model. Notice the fields marked REQUIRED; these are essential for any state model definition.
+
+```
+StateModelDefinition stateModel = new StateModelDefinition.Builder("MasterSlave")
+ // OFFLINE is the state that the system starts in (initial state is REQUIRED)
+ .initialState("OFFLINE")
+
+ // Lowest number here indicates highest priority, no value indicates lowest priority
+ .addState("MASTER", 1)
+ .addState("SLAVE", 2)
+ .addState("OFFLINE")
+
+ // Note the special inclusion of the DROPPED state (REQUIRED)
+ .addState(HelixDefinedState.DROPPED.toString())
+
+ // No more than one master allowed
+ .upperBound("MASTER", 1)
+
+ // R indicates an upper bound of number of replicas for each partition
+ .dynamicUpperBound("SLAVE", "R")
+
+ // Add some high-priority transitions
+ .addTransition("SLAVE", "MASTER", 1)
+ .addTransition("OFFLINE", "SLAVE", 2)
+
+ // Using the same priority value indicates that these transitions can fire in any order
+ .addTransition("MASTER", "SLAVE", 3)
+ .addTransition("SLAVE", "OFFLINE", 3)
+
+ // Not specifying a value defaults to lowest priority
+ // Notice the inclusion of the OFFLINE to DROPPED transition
+ // Since every state has a path to OFFLINE, they each now have a path to DROPPED (REQUIRED)
+ .addTransition("OFFLINE", HelixDefinedState.DROPPED.toString())
+
+ // Create the StateModelDefinition instance
+ .build();
+
+ // Use the isValid() function to make sure the StateModelDefinition will work without issues
+ Assert.assertTrue(stateModel.isValid());
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_task_framework.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Task Framework</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Task Framework
+
+Task framework, in Helix, provides executable task scheduling and workflow management. In Helix, three layers of task abstraction have been offered to user for defining their logics of dependencies. The graph shows the relationships between three layers. Workflow can contain multiple jobs. One job can depend on other one. Multiple tasks, including same task different partition and different task different partition, can be added in one job.
+Task framework not only can abstract three layers task logics but also helps doing task assignment and rebalancing. User can create a workflow (or a job queue) at first beginning. Then jobs can be added into workflow. Those jobs contain the executable tasks implemented by user. Once workflow is completed, Helix will schedule the works based on the condition user provided.
+
+
+
+### Key Concepts
+* Task is the basic unit in Helix task framework. It can represents the a single runnable logics that user prefer to execute for each partition (distributed units).
+* Job defines one time operation across all the partitions. It contains multiple Tasks and configuration of tasks, such as how many tasks, timeout per task and so on.
+* Workflow is directed acyclic graph represents the relationships and running orders of Jobs. In addition, a workflow can also provide customized configuration, for example, Job dependencies.
+* JobQueue is another type of Workflow. Different from normal one, JobQueue is not terminated until user kill it. Also JobQueue can keep accepting newly coming jobs.
+
+### Implement Your Task
+
+#### [Task Interface](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/Task.java)
+
+The task interface contains two methods: run and cancel. User can implement his or her own logic in run function and cancel / roll back logic in cancel function.
+
+```
+public class MyTask implements Task {
+ @Override
+ TaskResult run() {
+ // Task logic
+ }
+
+ @Override
+ void cancel() {
+ // Cancel logic
+ }
+}
+```
+
+#### [TaskConfig](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/TaskConfig.java)
+
+In helix, usually an object config represents the abstraction of that object, such as TaskConfig, JobConfig and WorkflowConfig. TaskConfig contains configurable task conditions. TaskConfig does not require to have any input to create a new object:
+
+```
+TaskConfig taskConfig = new TaskConfig(null, null, null, null);
+```
+
+For these four fields:
+* Command: The task command, will use Job command if this is null
+* ID: Task unique id, will generate a new ID for this task if input is null
+* TaskTargetPartition: Target partition of a target. Could be null
+* ConfigMap: Task property key-value map containing all other property stated above, such as command, ID.
+
+#### Share Content Across Tasks and Jobs
+
+Task framework also provides a feature that user can store the key-value data per task, job and workflow. The content stored at workflow layer can shared by different jobs belong to this workflow. Similarly content persisted at job layer can shared by different tasks nested in this job. Currently, user can extend the abstract class [UserContentStore](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/UserContentStore.java) and use two methods putUserContent and getUserContent. It will similar to hash map put and get method except a Scope. The Scope will define which layer this key-value pair to be persisted.
+
+```
+public class MyTask extends UserContentStore implements Task {
+ @Override
+ TaskResult run() {
+ putUserContent("KEY", "WORKFLOWVALUE", SCOPE.WORKFLOW);
+ putUserContent("KEY", "JOBVALUE", SCOPE.JOB);
+ putUserContent("KEY", "TASKVALUE", SCOPE.TASK);
+ String taskValue = getUserContent("KEY", SCOPE.TASK);
+ }
+ ...
+}
+```
+
+#### Return [Task Results](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/TaskResult.java)
+
+User can define the TaskResult for a task once it is at final stage (complete or failed). The TaskResult contains two fields: status and info. Status is current Task Status including COMPLETED, CANCELLED, FAILED and FATAL_FAILED. The difference between FAILED and FATAL_FAILED is that once the task defined as FATAL_FAILED, helix will not do the retry for this task and abort it. The other field is information, which is a String type. User can pass any information including error message, description and so on.
+
+```
+TaskResult run() {
+ ....
+ return new TaskResult(TaskResult.Status.FAILED, "ERROR MESSAGE OR OTHER INFORMATION");
+}
+```
+
+#### Task Retry and Abort
+
+Helix provides retry logics to users. User can specify the how many times allowed to tolerant failure of tasks under a job. It is a method will be introduced in Following Job Section. Another choice offered to user that if user thinks a task is very critical and do not want to do the retry once it is failed, user can return a TaskResult stated above with FATAL_FAILED status. Then Helix will not do the retry for that task.
+
+```
+return new TaskResult(TaskResult.Status.FATAL_FAILED, "DO NOT WANT TO RETRY, ERROR MESSAGE");
+```
+
+#### [TaskDriver](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/TaskDriver.java)
+
+All the control operation related to workflow and job are based on TaskDriver object. TaskDriver offers several APIs to controller, modify and track the tasks. Those APIs will be introduced in each section when they are necessary. TaskDriver object can be created either by [HelixManager](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/HelixManager.java) or [ZkClient](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/manager/zk/ZkClient.java) with cluster name:
+
+```
+HelixManager manager = new ZKHelixManager(CLUSTER_NAME, INSTANCE_NAME, InstanceType.PARTICIPANT, ZK_ADDRESS);
+TaskDriver taskDriver1 = new TaskDriver(manager);
+
+TaskDriver taskDriver2 = new TaskDriver(zkclient, CLUSTER_NAME);
+```
+
+#### Propagate Task Error Message to Helix
+
+When task encounter an error, it could be returned by TaskResult. Unfortunately, user can not get this TaskResult object directly. But Helix provides error messages persistent. Thus user can fetch the error messages from Helix via TaskDriver, which introduced above. The error messages will be stored in Info field per Job. Thus user have to get JobContext, which is the job status and result object.
+
+```
+taskDriver.getJobContext("JOBNAME").getInfo();
+```
+
+### Creating a Workflow
+
+#### One-time Workflow
+
+As common use, one-time workflow will be the default workflow as user created. The first step is to create a WorkflowConfig.Builder object with workflow name. Then all configs can be set in WorkflowConfig.Builder. Once the configuration is done, [WorkflowConfig](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/WorkflowConfig.java) object can be got from WorkflowConfig.Builder object.
+We have two rules to validate the Workflow configuration:
+* Expiry time should not be less than 0
+* Schedule config should be valid either one-time or a positive interval magnitude (Recurrent workflow)
+Example:
+
+```
+Workflow.Builder myWorkflowBuilder = new Workflow.Builder("MyWorkflow");
+myWorkflowBuilder.setExpiry(5000L);
+Workflow myWorkflow = myWorkflowBuilder.build();
+```
+
+#### Recurrent Workflow
+
+Recurrent workflow is the workflow scheduled periodically. The only config different from One-time workflow is to set a recurrent [ScheduleConfig](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/ScheduleConfig.java). There two methods in ScheduleConfig can help you to create a ScheduleConfig object: recurringFromNow and recurringFromDate. Both of them needs recurUnit (time unit for recurrent) and recurInteval (magnitude of recurrent interval). Here's the example:
+
+```
+ScheduleConfig myConfig1 = ScheduleConfig.recurringFFromNow(TimeUnit.MINUTES, 5L);
+ScheduleConfig myConfig2 = ScheduleConfig.recurringFFromDate(Calendar.getInstance.getTime, TimeUnit.HOURS, 10L);
+```
+
+Once this schedule config is created. It could be set in the workflow config:
+
+```
+Workflow.Builder myWorkflowBuilder = new Workflow.Builder("MyWorkflow");
+myWorkflowBuilder.setExpiry(2000L)
+ .setScheduleConfig(ScheduleConfig.recurringFromNow(TimeUnit.DAYS, 5));
+Workflow myWorkflow = myWorkflowBuilder.build();
+```
+
+#### Start a Workflow
+
+Start a workflow is just using taskdrive to start it. Since this is an async call, after start the workflow, user can keep doing actions.
+
+```
+taskDriver.start(myWorkflow);
+```
+
+#### Stop a Workflow
+
+Stop workflow can be executed via TaskDriver:
+
+```
+taskDriver.stop(myWorkflow);
+```
+
+#### Resume a Workflow
+
+Once the workflow is stopped, it does not mean the workflow is gone. Thus user can resume the workflow that has been stopped. Using TaskDriver resume the workflow:
+
+```
+taskDriver.resume(myWorkflow);
+```
+
+#### Delete a Workflow
+
+Simliar to start, stop and resume, delete operation is supported by TaskDriver.
+
+```
+taskDriver.delete(myWorkflow);
+```
+
+#### Add a Job
+
+WARNING: Job can only be added to WorkflowConfig.Builder. Once WorkflowConfig built, no job can be added! For creating a Job, please refering following section (Create a Job)
+
+```
+myWorkflowBuilder.addJob("JobName", jobConfigBuilder);
+```
+
+#### Add a Job dependency
+
+Jobs can have dependencies. If one job2 depends job1, job2 will not be scheduled until job1 finished.
+
+```
+myWorkflowBuilder.addParentChildDependency(ParentJobName, ChildJobName);
+```
+
+#### Additional Workflow Options
+
+| Additional Config Options | Detail |
+| ------------------------- | ------ |
+| _setJobDag(JobDag v)_ | If user already defined the job DAG, it could be set with this method. |
+| _setExpiry(long v, TimeUnit unit)_ | Set the expiration time for this workflow. |
+| _setFailureThreshold(int failureThreshold)_ | Set the failure threshold for this workflow, once job failures reach this number, the workflow will be failed. |
+| _setWorkflowType(String workflowType)_ | Set the user defined workflowType for this workflow. |
+| _setTerminable(boolean isTerminable)_ | Set the whether this workflow is terminable or not. |
+| _setCapacity(int capacity)_ | Set the number of jobs that workflow can hold before reject further jobs. Only used when workflow is not terminable. |
+| _setTargetState(TargetState v)_ | Set the final state of this workflow. |
+
+### Creating a Queue
+
+[Job queue](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/JobQueue.java) is another shape of workflow. Here listed different between a job queue and workflow:
+
+| Property | Workflow | Job Queue |
+| -------- | -------- | --------- |
+| Existing time | Workflow will be deleted after it is done. | Job queue will be there until user delete it. |
+| Add jobs | Once workflow is build, no job can be added. | Job queue can keep accepting jobs. |
+| Parallel run | Allows parallel run for jobs without dependencies | No parallel run allowed except setting _ParallelJobs_ |
+
+For creating a job queue, user have to provide queue name and workflow config (please refer above Create a Workflow). Similar to other task object, create a JobQueue.Builder first. Then JobQueue can be validated and generated via build function.
+
+```
+WorkflowConfig.Builder myWorkflowCfgBuilder = new WorkflowConfig.Builder().setWorkFlowType("MyType");
+JobQueue jobQueue = new JobQueue.Builder("MyQueueName").setWorkflowConfig(myWorkflowCfgBuilder.build()).build();
+```
+
+####Append Job to Queue
+
+WARNING:Different from normal workflow, job for JobQueue can be append even in anytime. Similar to workflow add a job, job can be appended via enqueueJob function via TaskDriver.
+
+```
+jobQueueBuilder.enqueueJob("JobName", jobConfigBuilder);
+```
+
+####Delete Job from Queue
+
+Helix allowed user to delete a job from existing queue. We offers delete API in TaskDriver to do this. Delete job from queue and this queue has to be stopped. Then user can resume the job once delete success.
+
+```
+taskDriver.stop("QueueName");
+taskDriver.deleteJob("QueueName", "JobName");
+taskDriver.resume("QueueName");
+```
+
+####Additional Option for JobQueue
+
+_setParallelJobs(int parallelJobs)_ : Set the how many jobs can parallel running, except there is any dependencies.
+
+###Create a Job
+
+Before generate a [JobConfig](https://github.com/apache/helix/blob/helix-0.6.x/helix-core/src/main/java/org/apache/helix/task/JobConfig.java) object, user still have to use JobConfig.Builder to build JobConfig.
+
+```
+JobConfig.Builder myJobCfgBuilder = new JobConfig.Builder();
+JobConfig myJobCfg = myJobCfgBuilder.build();
+```
+
+Helix has couple rules to validate a job:
+* Each job must at least have one task to execute. For adding tasks and task rules please refer following section Add Tasks.
+* Task timeout should not less than zero.
+* Number of concurrent tasks per instances should not less than one.
+* Maximum attempts per task should not less than one
+* There must be a workflow name
+
+#### Add Tasks
+
+There are two ways of adding tasks:
+* Add by TaskConfig. Tasks can be added via adding TaskConfigs. User can create a List of TaskConfigs or add TaskConfigMap, which is a task id to TaskConfig mapping.
+
+```
+TaskConfig taskCfg = new TaskConfig(null, null, null, null);
+List<TaskConfig> taskCfgs = new ArrayList<TaskConfig>();
+myJobCfg.addTaskConfigs(taskCfgs);
+
+Map<String, TaskConfig> taskCfgMap = new HashMap<String, TaskConfig>();
+taskCfgMap.put(taskCfg.getId(), taskCfg);
+myJobCfg.addTaskConfigMap(taskCfgMap);
+```
+
+* Add by Job command. If user does not want to specify each TaskConfig, we can create identical tasks based on Job command with number of tasks.
+
+```
+myJobCfg.setCommand("JobCommand").setNumberOfTasks(10);
+```
+WARNING: Either user provides TaskConfigs / TaskConfigMap or both of Job command and number tasks (except Targeted Job, refer following section) . Otherwise, validation will be failed.
+
+#### Generic Job
+
+Generic Job is the default job created. It does not have targeted resource. Thus this generic job could be assigned to one of eligble instances.
+
+#### Targeted Job
+
+Targeted Job has set up the target resource. For this kind of job, Job command is necessary, but number of tasks is not. The tasks will depends on the partion number of targeted resource. To set target resource, just put target resource name to JobConfig.Builder.
+
+```
+myJobCfgBuilder.setTargetResource("TargetResourceName");
+```
+
+In addition, user can specify the instance target state. For example, if user want to run the Task on "Master" state instance, setTargetPartitionState method can help to set the partition to assign to specific instance.
+
+```
+myJobCfgBuilder.setTargetPartitionState(Arrays.asList(new String[]{"Master", "Slave"}));
+```
+
+#### Instance Group
+
+Grouping jobs with targeted group of instances feature has been supported. User firstly have to define the instance group tag for instances, which means label some instances with specific tag. Then user can put those tags to a job that only would like to assigned to those instances. For example, customer data only available on instance 1, 2, 3. These three instances can be tagged as "CUSTOMER" and customer data related jobs can set the instance group tag "CUSTOMER". Thus customer data related jobs will only assign to instance 1, 2, 3.
+To add instance group tag, just set it in JobConfig.Builder:
+
+```
+jobCfg.setInstanceGroupTag("INSTANCEGROUPTAG");
+```
+
+#### Additional Job Options
+
+| Operation | Detail |
+| --------- | ------ |
+| _setWorkflow(String workflowName)_ | Set the workflow that this job belongs to |
+| _setTargetPartions(List\<String\> targetPartionNames)_ | Set list of partition names |
+| _setTargetPartionStates(Set\<String\>)_ | Set the partition states |
+| _setCommand(String command)_ | Set the job command |
+| _setJobCommandConfigMap(Map\<String, String\> v)_ | Set the job command config maps |
+| _setTimeoutPerTask(long v)_ | Set the timeout for each task |
+| _setNumConcurrentTasksPerInstance(int v)_ | Set number of tasks can concurrent run on same instance |
+| _setMaxAttemptsPerTask(int v)_ | Set times of retry for a task |
+| _setFailureThreshold(int v)_ | Set failure tolerance of tasks for this job |
+| _setTaskRetryDelay(long v)_ | Set the delay time before a task retry |
+| _setIgnoreDependentJobFailure(boolean ignoreDependentJobFailure)_ | Set whether ignore the job failure of parent job of this job |
+| _setJobType(String jobType)_ | Set the job type of this job |
+
+### Monitor the status of your job
+As we introduced the excellent util TaskDriver in Workflow Section, we have extra more functionality that provided to user. The user can synchronized wait Job or Workflow until it reaches certain STATES. The function Helix have API pollForJobState and pollForWorkflowState. For pollForJobState, it accepts arguments:
+* Workflow name, required
+* Job name, required
+* Timeout, not required, will be three minutes if user choose function without timeout argument. Time unit is milisecond.
+* TaskStates, at least one state. This function can accept multiple TaskState, will end function until one of those TaskState reaches.
+For example:
+
+```
+taskDriver.pollForJobState("MyWorkflowName", "MyJobName", 180000L, TaskState.FAILED, TaskState.FATAL_FAILED);
+taskDriver.pollForJobState("MyWorkflowName", "MyJobName", TaskState.COMPLETED);
+```
+
+For pollForWorkflowState, it accepts similar arguments except Job name. For example:
+
+```
+taskDriver.pollForWorkflowState("MyWorkflowName", 180000L, TaskState.FAILED, TaskState.FATAL_FAILED);
+taskDriver.pollForWorkflowState("MyWorkflowName", TaskState.COMPLETED);
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_throttling.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Throttling</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Throttling
+
+In this chapter, we\'ll learn how to control the parallel execution of cluster tasks. Only a centralized cluster manager with global knowledge (i.e. Helix) is capable of coordinating this decision.
+
+### Throttling
+
+Since all state changes in the system are triggered through transitions, Helix can control the number of transitions that can happen in parallel. Some of the transitions may be lightweight, but some might involve moving data, which is quite expensive from a network and IOPS perspective.
+
+Helix allows applications to set a threshold on transitions. The threshold can be set at multiple scopes:
+
+* MessageType e.g STATE_TRANSITION
+* TransitionType e.g SLAVE-MASTER
+* Resource e.g database
+* Node i.e per-node maximum transitions in parallel
+
+
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_user_def_rebalancer.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - User-Defined Rebalancing</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): User-Defined Rebalancing
+
+Even though Helix can compute both the location and the state of replicas internally using a default fully-automatic rebalancer, specific applications may require rebalancing strategies that optimize for different requirements. Thus, Helix allows applications to plug in arbitrary rebalancer algorithms that implement a provided interface. One of the main design goals of Helix is to provide maximum flexibility to any distributed application. Thus, it allows applications to fully implement the rebalancer, which is the core constraint solver in the system, if the application developer so chooses.
+
+Whenever the state of the cluster changes, as is the case when participants join or leave the cluster, Helix automatically calls the rebalancer to compute a new mapping of all the replicas in the resource. When using a pluggable rebalancer, the only required step is to register it with Helix. Subsequently, no additional bootstrapping steps are necessary. Helix uses reflection to look up and load the class dynamically at runtime. As a result, it is also technically possible to change the rebalancing strategy used at any time.
+
+The Rebalancer interface is as follows:
+
+```
+void init(HelixManager manager);
+
+IdealState computeNewIdealState(String resourceName, IdealState currentIdealState,
+ final CurrentStateOutput currentStateOutput, final ClusterDataCache clusterData);
+```
+The first parameter is the resource to rebalance, the second is pre-existing ideal mappings, the third is a snapshot of the actual placements and state assignments, and the fourth is a full cache of all of the cluster data available to Helix. Internally, Helix implements the same interface for its own rebalancing routines, so a user-defined rebalancer will be cognizant of the same information about the cluster as an internal implementation. Helix strives to provide applications the ability to implement algorithms that may require a large portion of the entire state of the cluster to make the best placement and state assignment decisions possible.
+
+An IdealState is a full representation of the location of each replica of each partition of a given resource. This is a simple representation of the placement that the algorithm believes is the best possible. If the placement meets all defined constraints, this is what will become the actual state of the distributed system.
+
+### Specifying a Rebalancer
+For implementations that set up the cluster through existing code, the following HelixAdmin calls will update the Rebalancer class:
+
+```
+IdealState idealState = helixAdmin.getResourceIdealState(clusterName, resourceName);
+idealState.setRebalanceMode(RebalanceMode.USER_DEFINED);
+idealState.setRebalancerClassName(className);
+helixAdmin.setResourceIdealState(clusterName, resourceName, idealState);
+```
+
+There are two key fields to set to specify that a pluggable rebalancer should be used. First, the rebalance mode should be set to USER_DEFINED, and second the rebalancer class name should be set to a class that implements Rebalancer and is within the scope of the project. The class name is a fully-qualified class name consisting of its package and its name. Without specification of the USER_DEFINED mode, the user-defined rebalancer class will not be used even if specified. Furthermore, Helix will not attempt to rebalance the resources through its standard routines if its mode is USER_DEFINED, regardless of whether or not a rebalancer class is registered.
+
+### Example
+
+In the next release (0.7.0), we will provide a full recipe of a user-defined rebalancer in action.
+
+Consider the case where partitions are locks in a lock manager and 6 locks are to be distributed evenly to a set of participants, and only one participant can hold each lock. We can define a rebalancing algorithm that simply takes the modulus of the lock number and the number of participants to evenly distribute the locks across participants. Helix allows capping the number of partitions a participant can accept, but since locks are lightweight, we do not need to define a restriction in this case. The following is a succinct implementation of this algorithm.
+
+```
+@Override
+IdealState computeNewIdealState(String resourceName, IdealState currentIdealState,
+ final CurrentStateOutput currentStateOutput, final ClusterDataCache clusterData) {
+ // Get the list of live participants in the cluster
+ List<String> liveParticipants = new ArrayList<String>(clusterData.getLiveInstances().keySet());
+
+ // Count the number of participants allowed to lock each lock (in this example, this is 1)
+ int lockHolders = Integer.parseInt(currentIdealState.getReplicas());
+
+ // Fairly assign the lock state to the participants using a simple mod-based sequential
+ // assignment. For instance, if each lock can be held by 3 participants, lock 0 would be held
+ // by participants (0, 1, 2), lock 1 would be held by (1, 2, 3), and so on, wrapping around the
+ // number of participants as necessary.
+ int i = 0;
+ for (String partition : currentIdealState.getPartitionSet()) {
+ List<String> preferenceList = new ArrayList<String>();
+ for (int j = i; j < i + lockHolders; j++) {
+ int participantIndex = j % liveParticipants.size();
+ String participant = liveParticipants.get(participantIndex);
+ // enforce that a participant can only have one instance of a given lock
+ if (!preferenceList.contains(participant)) {
+ preferenceList.add(participant);
+ }
+ }
+ currentIdealState.setPreferenceList(partition, preferenceList);
+ i++;
+ }
+ return assignment;
+}
+```
+
+Here are the IdealState preference lists emitted by the user-defined rebalancer for a 3-participant system whenever there is a change to the set of participants.
+
+* Participant_A joins
+
+```
+{
+ "lock_0": ["Participant_A"],
+ "lock_1": ["Participant_A"],
+ "lock_2": ["Participant_A"],
+ "lock_3": ["Participant_A"],
+ "lock_4": ["Participant_A"],
+ "lock_5": ["Participant_A"],
+}
+```
+
+A preference list is a mapping for each resource of partition to the participants serving each replica. The state model is a simple LOCKED/RELEASED model, so participant A holds all lock partitions in the LOCKED state.
+
+* Participant_B joins
+
+```
+{
+ "lock_0": ["Participant_A"],
+ "lock_1": ["Participant_B"],
+ "lock_2": ["Participant_A"],
+ "lock_3": ["Participant_B"],
+ "lock_4": ["Participant_A"],
+ "lock_5": ["Participant_B"],
+}
+```
+
+Now that there are two participants, the simple mod-based function assigns every other lock to the second participant. On any system change, the rebalancer is invoked so that the application can define how to redistribute its resources.
+
+* Participant_C joins (steady state)
+
+```
+{
+ "lock_0": ["Participant_A"],
+ "lock_1": ["Participant_B"],
+ "lock_2": ["Participant_C"],
+ "lock_3": ["Participant_A"],
+ "lock_4": ["Participant_B"],
+ "lock_5": ["Participant_C"],
+}
+```
+
+This is the steady state of the system. Notice that four of the six locks now have a different owner. That is because of the naïve modulus-based assignmemt approach used by the user-defined rebalancer. However, the interface is flexible enough to allow you to employ consistent hashing or any other scheme if minimal movement is a system requirement.
+
+* Participant_B fails
+
+```
+{
+ "lock_0": ["Participant_A"],
+ "lock_1": ["Participant_C"],
+ "lock_2": ["Participant_A"],
+ "lock_3": ["Participant_C"],
+ "lock_4": ["Participant_A"],
+ "lock_5": ["Participant_C"],
+}
+```
+
+On any node failure, as in the case of node addition, the rebalancer is invoked automatically so that it can generate a new mapping as a response to the change. Helix ensures that the Rebalancer has the opportunity to reassign locks as required by the application.
+
+* Participant_B (or the replacement for the original Participant_B) rejoins
+
+```
+{
+ "lock_0": ["Participant_A"],
+ "lock_1": ["Participant_B"],
+ "lock_2": ["Participant_C"],
+ "lock_3": ["Participant_A"],
+ "lock_4": ["Participant_B"],
+ "lock_5": ["Participant_C"],
+}
+```
+
+The rebalancer was invoked once again and the resulting IdealState preference lists reflect the steady state.
+
+### Caveats
+- The rebalancer class must be available at runtime, or else Helix will not attempt to rebalance at all
+- The Helix controller will only take into account the preference lists in the new IdealState for this release. In 0.7.0, Helix rebalancers will be able to compute the full resource assignment, including the states.
+- Helix does not currently persist the new IdealState computed by the user-defined rebalancer. However, the Helix property store is available for saving any computed state. In 0.7.0, Helix will persist the result of running the rebalancer.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_yaml.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - YAML Cluster Setup</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): YAML Cluster Setup
+
+As an alternative to using Helix Admin to set up the cluster, its resources, constraints, and the state model, Helix supports bootstrapping a cluster configuration based on a YAML file. Below is an annotated example of such a file for a simple distributed lock manager where a lock can only be LOCKED or RELEASED, and each lock only allows a single participant to hold it in the LOCKED state.
+
+```
+clusterName: lock-manager-custom-rebalancer # unique name for the cluster (required)
+resources:
+ - name: lock-group # unique resource name (required)
+ rebalancer: # required
+ mode: USER_DEFINED # required - USER_DEFINED means we will provide our own rebalancer
+ class: org.apache.helix.userdefinedrebalancer.LockManagerRebalancer # required for USER_DEFINED
+ partitions:
+ count: 12 # number of partitions for the resource (default is 1)
+ replicas: 1 # number of replicas per partition (default is 1)
+ stateModel:
+ name: lock-unlock # model name (required)
+ states: [LOCKED, RELEASED, DROPPED] # the list of possible states (required if model not built-in)
+ transitions: # the list of possible transitions (required if model not built-in)
+ - name: Unlock
+ from: LOCKED
+ to: RELEASED
+ - name: Lock
+ from: RELEASED
+ to: LOCKED
+ - name: DropLock
+ from: LOCKED
+ to: DROPPED
+ - name: DropUnlock
+ from: RELEASED
+ to: DROPPED
+ - name: Undrop
+ from: DROPPED
+ to: RELEASED
+ initialState: RELEASED # (required if model not built-in)
+ constraints:
+ state:
+ counts: # maximum number of replicas of a partition that can be in each state (required if model not built-in)
+ - name: LOCKED
+ count: "1"
+ - name: RELEASED
+ count: "-1"
+ - name: DROPPED
+ count: "-1"
+ priorityList: [LOCKED, RELEASED, DROPPED] # states in order of priority (all priorities equal if not specified)
+ transition: # transitions priority to enforce order that transitions occur
+ priorityList: [Unlock, Lock, Undrop, DropUnlock, DropLock] # all priorities equal if not specified
+participants: # list of nodes that can serve replicas (optional if dynamic joining is active, required otherwise)
+ - name: localhost_12001
+ host: localhost
+ port: 12001
+ - name: localhost_12002
+ host: localhost
+ port: 12002
+ - name: localhost_12003
+ host: localhost
+ port: 12003
+```
+
+Using a file like the one above, the cluster can be set up either with the command line:
+
+```
+helix/helix-core/target/helix-core/pkg/bin/YAMLClusterSetup.sh localhost:2199 lock-manager-config.yaml
+```
+
+or with code:
+
+```
+YAMLClusterSetup setup = new YAMLClusterSetup(zkAddress);
+InputStream input =
+ Thread.currentThread().getContextClassLoader()
+ .getResourceAsStream("lock-manager-config.yaml");
+YAMLClusterSetup.YAMLClusterConfig config = setup.setupCluster(input);
+```
+
+Some notes:
+
+- A rebalancer class is only required for the USER_DEFINED mode. It is ignored otherwise.
+
+- Built-in state models, like OnlineOffline, LeaderStandby, and MasterSlave, or state models that have already been added only require a name for stateModel. If partition and/or replica counts are not provided, a value of 1 is assumed.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/resources/.htaccess
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+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+Redirect /download.html /download.cgi
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/resources/download.cgi
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+#!/bin/sh
+# Just call the standard mirrors.cgi script. It will use download.html
+# as the input template.
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License. You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+exec /www/www.apache.org/dyn/mirrors/mirrors.cgi $*
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/resources/images/PFS-Generic.png
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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!--
+ Licensed to the Apache Software Foundation (ASF) under one or more
+ contributor license agreements. See the NOTICE file distributed with
+ this work for additional information regarding copyright ownership.
+ The ASF licenses this file to You under the Apache License, Version 2.0
+ (the "License"); you may not use this file except in compliance with
+ the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+<project name="Apache Helix">
+ <bannerLeft>
+ <src>../images/helix-logo.jpg</src>
+ <href>http://helix.apache.org/</href>
+ </bannerLeft>
+ <bannerRight>
+ <src>../images/feather_small.gif</src>
+ <href>http://www.apache.org/</href>
+ </bannerRight>
+ <version position="none"/>
+
+ <publishDate position="right"/>
+
+ <skin>
+ <groupId>lt.velykis.maven.skins</groupId>
+ <artifactId>reflow-maven-skin</artifactId>
+ <version>1.0.0</version>
+ </skin>
+
+ <body>
+
+ <head>
+ <script type="text/javascript">
+
+ var _gaq = _gaq || [];
+ _gaq.push(['_setAccount', 'UA-3211522-12']);
+ _gaq.push(['_trackPageview']);
+
+ (function() {
+ var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
+ ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
+ var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
+ })();
+
+ </script>
+
+ </head>
+
+ <breadcrumbs position="left">
+ <item name="Apache Helix" href="http://helix.apache.org/"/>
+ <item name="Release 0.6.8" href="http://helix.apache.org/0.6.8-docs/"/>
+ </breadcrumbs>
+
+ <links>
+ <item name="Helix 0.6.8" href="./index.html"/>
+ </links>
+
+ <menu name="Get Helix">
+ <item name="Download" href="./download.html"/>
+ <item name="Building" href="./Building.html"/>
+ <item name="Release Notes" href="./releasenotes/release-0.6.8.html"/>
+ </menu>
+
+ <menu name="Hands-On">
+ <item name="Quick Start" href="./Quickstart.html"/>
+ <item name="Tutorial" href="./Tutorial.html"/>
+ <item name="Javadocs" href="http://helix.apache.org/javadocs/0.6.8"/>
+ </menu>
+
+ <menu name="Recipes">
+ <item name="Distributed lock manager" href="./recipes/lock_manager.html"/>
+ <item name="Rabbit MQ consumer group" href="./recipes/rabbitmq_consumer_group.html"/>
+ <item name="Rsync replicated file store" href="./recipes/rsync_replicated_file_store.html"/>
+ <item name="Service discovery" href="./recipes/service_discovery.html"/>
+ <item name="Distributed task DAG execution" href="./recipes/task_dag_execution.html"/>
+ </menu>
+<!--
+ <menu ref="reports" inherit="bottom"/>
+ <menu ref="modules" inherit="bottom"/>
+
+
+ <menu name="ASF">
+ <item name="How Apache Works" href="http://www.apache.org/foundation/how-it-works.html"/>
+ <item name="Foundation" href="http://www.apache.org/foundation/"/>
+ <item name="Sponsoring Apache" href="http://www.apache.org/foundation/sponsorship.html"/>
+ <item name="Thanks" href="http://www.apache.org/foundation/thanks.html"/>
+ </menu>
+-->
+ <footer>
+ <div class="row span16"><div>Apache Helix, Apache, the Apache feather logo, and the Apache Helix project logos are trademarks of The Apache Software Foundation.
+ All other marks mentioned may be trademarks or registered trademarks of their respective owners.</div>
+ <a href="${project.url}/privacy-policy.html">Privacy Policy</a>
+ </div>
+ </footer>
+
+
+ </body>
+
+ <custom>
+ <reflowSkin>
+ <theme>default</theme>
+ <highlightJs>false</highlightJs>
+ <brand>
+ <name>Apache Helix</name>
+ <href>http://helix.apache.org</href>
+ </brand>
+ <slogan>A cluster management framework for partitioned and replicated distributed resources</slogan>
+ <bottomNav>
+ <column>Get Helix</column>
+ <column>Hands-On</column>
+ <column>Recipes</column>
+ </bottomNav>
+ <pages>
+ <index>
+ <sections>
+ <columns>3</columns>
+ </sections>
+ </index>
+ </pages>
+ </reflowSkin>
+ <!--fluidoSkin>
+ <topBarEnabled>true</topBarEnabled>
+ <sideBarEnabled>true</sideBarEnabled>
+ <googleSearch></googleSearch>
+ <twitter>
+ <user>ApacheHelix</user>
+ <showUser>true</showUser>
+ <showFollowers>false</showFollowers>
+ </twitter>
+ </fluidoSkin-->
+ </custom>
+
+</project>
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+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+
+-->
+#set( $releaseName = "0.6.8" )
+#set( $releaseDate = "01/20/2017" )
+<document xmlns="http://maven.apache.org/XDOC/2.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
+
+ <properties>
+ <title>Apache Helix Downloads</title>
+ <author email="dev@helix.apache.org">Apache Helix Documentation Team</author>
+ </properties>
+
+ <body>
+ <div class="toc_container">
+ <macro name="toc">
+ <param name="class" value="toc"/>
+ </macro>
+ </div>
+
+ <section name="Introduction">
+ <p>Apache Helix artifacts are distributed in source and binary form under the terms of the
+ <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.
+ See the included <tt>LICENSE</tt> and <tt>NOTICE</tt> files included in each artifact for additional license
+ information.
+ </p>
+ <p>Use the links below to download a source distribution of Apache Helix.
+ It is good practice to <a href="#Verifying_Releases">verify the integrity</a> of the distribution files.</p>
+ </section>
+
+ <section name="Release">
+ <p>Release date: ${releaseDate} </p>
+ <p><a href="releasenotes/release-${releaseName}.html">${releaseName} Release notes</a></p>
+ <a name="mirror"/>
+ <subsection name="Mirror">
+
+ <p>
+ [if-any logo]
+ <a href="[link]">
+ <img align="right" src="[logo]" border="0"
+ alt="logo"/>
+ </a>
+ [end]
+ The currently selected mirror is
+ <b>[preferred]</b>.
+ If you encounter a problem with this mirror,
+ please select another mirror.
+ If all mirrors are failing, there are
+ <i>backup</i>
+ mirrors
+ (at the end of the mirrors list) that should be available.
+ </p>
+
+ <form action="[location]" method="get" id="SelectMirror" class="form-inline">
+ Other mirrors:
+ <select name="Preferred" class="input-xlarge">
+ [if-any http]
+ [for http]
+ <option value="[http]">[http]</option>
+ [end]
+ [end]
+ [if-any ftp]
+ [for ftp]
+ <option value="[ftp]">[ftp]</option>
+ [end]
+ [end]
+ [if-any backup]
+ [for backup]
+ <option value="[backup]">[backup] (backup)</option>
+ [end]
+ [end]
+ </select>
+ <input type="submit" value="Change" class="btn"/>
+ </form>
+
+ <p>
+ You may also consult the
+ <a href="http://www.apache.org/mirrors/">complete list of mirrors.</a>
+ </p>
+
+ </subsection>
+ <subsection name="${releaseName} Sources">
+ <table>
+ <thead>
+ <tr>
+ <th>Artifact</th>
+ <th>Signatures</th>
+ <th>Hashes</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>
+ <a href="[preferred]helix/${releaseName}/src/helix-${releaseName}-src.zip">helix-${releaseName}-src.zip</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/src/helix-${releaseName}-src.zip.asc">asc</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/src/helix-${releaseName}-src.zip.md5">md5</a>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/src/helix-${releaseName}-src.zip.sha1">sha1</a>
+ </td>
+ </tr>
+ </tbody>
+ </table>
+ </subsection>
+ <subsection name="${releaseName} Binaries">
+ <table>
+ <thead>
+ <tr>
+ <th>Artifact</th>
+ <th>Signatures</th>
+ <th>Hashes</th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <td>
+ <a href="[preferred]helix/${releaseName}/binaries/helix-core-${releaseName}-pkg.tar">helix-core-${releaseName}-pkg.tar</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-core-${releaseName}-pkg.tar.asc">asc</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-core-${releaseName}-pkg.tar.md5">md5</a>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-core-${releaseName}-pkg.tar.sha1">sha1</a>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <a href="[preferred]helix/${releaseName}/binaries/helix-admin-webapp-${releaseName}-pkg.tar">helix-admin-webapp-${releaseName}-pkg.tar</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-admin-webapp-${releaseName}-pkg.tar.asc">asc</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-admin-webapp-${releaseName}-pkg.tar.md5">md5</a>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-admin-webapp-${releaseName}-pkg.tar.sha1">sha1</a>
+ </td>
+ </tr>
+ <tr>
+ <td>
+ <a href="[preferred]helix/${releaseName}/binaries/helix-agent-${releaseName}-pkg.tar">helix-agent-${releaseName}-pkg.tar</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-agent-${releaseName}-pkg.tar.asc">asc</a>
+ </td>
+ <td>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-agent-${releaseName}-pkg.tar.md5">md5</a>
+ <a href="http://www.apache.org/dist/helix/${releaseName}/binaries/helix-agent-${releaseName}-pkg.tar.sha1">sha1</a>
+ </td>
+ </tr>
+ </tbody>
+ </table>
+ </subsection>
+ </section>
+
+<!-- <section name="Older Releases">
+ </section>-->
+
+ <section name="Verifying Releases">
+ <p>It is essential that you verify the integrity of the downloaded file using the PGP signature (<tt>.asc</tt> file) or a hash (<tt>.md5</tt> or <tt>.sha1</tt> file). Please read <a href="http://www.apache.org/info/verification.html">Verifying Apache Software Foundation Releases</a> for more information on why you should verify our releases.</p>
+ <p>The PGP signature can be verified using <a href="http://www.pgpi.org/">PGP</a> or <a href="http://www.gnupg.org/">GPG</a>. First download the <a href="http://www.apache.org/dist/helix/KEYS">KEYS</a> as well as the <tt>*.asc</tt> signature files for the relevant distribution. Make sure you get these files from the main distribution site, rather than from a mirror. Then verify the signatures using one of the following sets of commands:
+
+ <source>% pgpk -a KEYS
+% pgpv downloaded_file.asc</source>
+
+ or<br/>
+
+ <source>% pgp -ka KEYS
+% pgp downloaded_file.asc</source>
+
+ or<br/>
+
+ <source>% gpg --import KEYS
+% gpg --verify downloaded_file.asc</source>
+ </p>
+ <p>Alternatively, you can verify the MD5 signature on the files. A Unix/Linux program called
+ <code>md5</code> or
+ <code>md5sum</code> is included in most distributions. It is also available as part of
+ <a href="http://www.gnu.org/software/textutils/textutils.html">GNU Textutils</a>.
+ Windows users can get binary md5 programs from these (and likely other) places:
+ <ul>
+ <li>
+ <a href="http://www.md5summer.org/">http://www.md5summer.org/</a>
+ </li>
+ <li>
+ <a href="http://www.fourmilab.ch/md5/">http://www.fourmilab.ch/md5/</a>
+ </li>
+ <li>
+ <a href="http://www.pc-tools.net/win32/md5sums/">http://www.pc-tools.net/win32/md5sums/</a>
+ </li>
+ </ul>
+ </p>
+ </section>
+ </body>
+</document>
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/test/conf/testng.xml
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/test/conf/testng.xml b/website/0.6.8/src/test/conf/testng.xml
new file mode 100644
index 0000000..58f0803
--- /dev/null
+++ b/website/0.6.8/src/test/conf/testng.xml
@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+<!DOCTYPE suite SYSTEM "http://testng.org/testng-1.0.dtd">
+<suite name="Suite" parallel="none">
+ <test name="Test" preserve-order="false">
+ <packages>
+ <package name="org.apache.helix"/>
+ </packages>
+ </test>
+</suite>
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/pom.xml
----------------------------------------------------------------------
diff --git a/website/pom.xml b/website/pom.xml
index 725f5ed..c5b38ae 100644
--- a/website/pom.xml
+++ b/website/pom.xml
@@ -39,6 +39,7 @@ under the License.
<module>0.6.5</module>
<module>0.6.6</module>
<module>0.6.7</module>
+ <module>0.6.8</module>
<module>0.7.0-incubating</module>
<module>0.7.1</module>
</modules>
[2/3] helix git commit: Prepare website for 0.6.8 release and add
0.6.8 release notes.
Posted by jx...@apache.org.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/recipes/rsync_replicated_file_store.md
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/markdown/recipes/rsync_replicated_file_store.md b/website/0.6.8/src/site/markdown/recipes/rsync_replicated_file_store.md
new file mode 100644
index 0000000..7338bcb
--- /dev/null
+++ b/website/0.6.8/src/site/markdown/recipes/rsync_replicated_file_store.md
@@ -0,0 +1,162 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Near-Realtime Rsync Replicated File System
+------------------------------------------
+
+### Quick Demo
+
+* This demo starts 3 instances with id's as ```localhost_12001, localhost_12002, localhost_12003```
+* Each instance stores its files under ```/tmp/<id>/filestore```
+* ```localhost_12001``` is designated as the master, and ```localhost_12002``` and ```localhost_12003``` are the slaves
+* Files written to the master are replicated to the slaves automatically. In this demo, a.txt and b.txt are written to ```/tmp/localhost_12001/filestore``` and they get replicated to other folders.
+* When the master is stopped, ```localhost_12002``` is promoted to master.
+* The other slave ```localhost_12003``` stops replicating from ```localhost_12001``` and starts replicating from new master ```localhost_12002```
+* Files written to new master ```localhost_12002``` are replicated to ```localhost_12003```
+* In the end state of this quick demo, ```localhost_12002``` is the master and ```localhost_12003``` is the slave. Manually create files under ```/tmp/localhost_12002/filestore``` and see that appear in ```/tmp/localhost_12003/filestore```
+* Ignore the interrupted exceptions on the console :-)
+
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+cd recipes/rsync-replicated-file-system/
+mvn clean install package -DskipTests
+cd target/rsync-replicated-file-system-pkg/bin
+chmod +x *
+./quickdemo
+
+```
+
+### Overview
+
+There are many applications that require storage for storing large number of relatively small data files. Examples include media stores to store small videos, images, mail attachments etc. Each of these objects is typically kilobytes, often no larger than a few megabytes. An additional distinguishing feature of these use cases is that files are typically only added or deleted, rarely updated. When there are updates, they do not have any concurrency requirements.
+
+These are much simpler requirements than what general purpose distributed file system have to satisfy; these would include concurrent access to files, random access for reads and updates, posix compliance, and others. To satisfy those requirements, general DFSs are also pretty complex that are expensive to build and maintain.
+
+A different implementation of a distributed file system includes HDFS which is inspired by Google's GFS. This is one of the most widely used distributed file system that forms the main data storage platform for Hadoop. HDFS is primary aimed at processing very large data sets and distributes files across a cluster of commodity servers by splitting up files in fixed size chunks. HDFS is not particularly well suited for storing a very large number of relatively tiny files.
+
+### File Store
+
+It's possible to build a vastly simpler system for the class of applications that have simpler requirements as we have pointed out.
+
+* Large number of files but each file is relatively small
+* Access is limited to create, delete and get entire files
+* No updates to files that are already created (or it's feasible to delete the old file and create a new one)
+
+
+We call this system a Partitioned File Store (PFS) to distinguish it from other distributed file systems. This system needs to provide the following features:
+
+* CRD access to large number of small files
+* Scalability: Files should be distributed across a large number of commodity servers based on the storage requirement
+* Fault-tolerance: Each file should be replicated on multiple servers so that individual server failures do not reduce availability
+* Elasticity: It should be possible to add capacity to the cluster easily
+
+
+Apache Helix is a generic cluster management framework that makes it very easy to provide scalability, fault-tolerance and elasticity features.
+rsync can be easily used as a replication channel between servers so that each file gets replicated on multiple servers.
+
+### Design
+
+#### High Level
+
+* Partition the file system based on the file name
+* At any time a single writer can write, we call this a master
+* For redundancy, we need to have additional replicas called slave. Slaves can optionally serve reads
+* Slave replicates data from the master
+* When a master fails, a slave gets promoted to master
+
+#### Transaction Log
+
+Every write on the master will result in creation/deletion of one or more files. In order to maintain timeline consistency slaves need to apply the changes in the same order
+To facilitate this, the master logs each transaction in a file and each transaction is associated with an 64 bit ID in which the 32 LSB represents a sequence number and MSB represents the generation number
+The sequence number gets incremented on every transaction and the generation is incremented when a new master is elected
+
+#### Replication
+
+Replication is required for slaves to keep up with changes on the master. Every time the slave applies a change it checkpoints the last applied transaction ID.
+During restarts, this allows the slave to pull changes from the last checkpointed ID. Similar to master, the slave logs each transaction to the transaction logs but instead of generating new transaction ID, it uses the same ID generated by the master.
+
+
+#### Failover
+
+When a master fails, a new slave will be promoted to master. If the previous master node is reachable, then the new master will flush all the
+changes from previous the master before taking up mastership. The new master will record the end transaction ID of the current generation and then start a new generation
+with sequence starting from 1. After this the master will begin accepting writes.
+
+
+
+
+
+### Rsync-based Solution
+
+
+
+
+This application demonstrates a file store that uses rsync as the replication mechanism. One can envision a similar system where instead of using rsync, one
+can implement a custom solution to notify the slave of the changes and also provide an api to pull the change files.
+
+#### Concepts
+* file_store_dir: Root directory for the actual data files
+* change_log_dir: The transaction logs are generated under this folder
+* check_point_dir: The slave stores the check points ( last processed transaction) here
+
+#### Master
+* File server: This component supports file uploads and downloads and writes the files to ```file_store_dir```. This is not included in this application. The idea is that most applications have different ways of implementing this component and have some associated business logic. It is not hard to come up with such a component if needed.
+* File store watcher: This component watches the ```file_store_dir``` directory on the local file system for any changes and notifies the registered listeners of the changes
+* Change log generator: This registers as a listener of the file store watcher and on each notification logs the changes into a file under ```change_log_dir```
+
+#### Slave
+* File server: This component on the slave will only support reads
+* Cluster state observer: Slave observes the cluster state and is able to know who is the current master
+* Replicator: This has two subcomponents
+ - Periodic rsync of change log: This is a background process that periodically rsyncs the ```change_log_dir``` of the master to its local directory
+ - Change Log Watcher: This watches the ```change_log_dir``` for changes and notifies the registered listeners of the change
+ - On demand rsync invoker: This is registered as a listener to change log watcher and on every change invokes rsync to sync only the changed file
+
+#### Coordination
+
+The coordination between nodes is done by Helix. Helix does the partition management and assigns the partition to multiple nodes based on the replication factor. It elects one the nodes as master and designates others as slaves.
+It provides notifications to each node in the form of state transitions (Offline to Slave, Slave to Master). It also provides notifications when there is change is cluster state.
+This allows the slave to stop replicating from current master and start replicating from new master.
+
+In this application, we have only one partition but its very easy to extend it to support multiple partitions. By partitioning the file store, one can add new nodes and Helix will automatically
+re-distribute partitions among the nodes. To summarize, Helix provides partition management, fault tolerance and facilitates automated cluster expansion.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/recipes/service_discovery.md
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/markdown/recipes/service_discovery.md b/website/0.6.8/src/site/markdown/recipes/service_discovery.md
new file mode 100644
index 0000000..c642c96
--- /dev/null
+++ b/website/0.6.8/src/site/markdown/recipes/service_discovery.md
@@ -0,0 +1,184 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+Service Discovery
+-----------------
+
+One of the common usage of ZooKeeper is to enable service discovery.
+The basic idea is that when a server starts up it advertises its configuration/metadata such as its hostname and port on ZooKeeper.
+This allows clients to dynamically discover the servers that are currently active. One can think of this like a service registry to which a server registers when it starts and
+is automatically deregistered when it shutdowns or crashes. In many cases it serves as an alternative to VIPs.
+
+The core idea behind this is to use ZooKeeper ephemeral nodes. The ephemeral nodes are created when the server registers and all its metadata is put into a ZNode.
+When the server shutdowns, ZooKeeper automatically removes this ZNode.
+
+There are two ways the clients can dynamically discover the active servers:
+
+### ZooKeeper Watch
+
+Clients can set a child watch under specific path on ZooKeeper.
+When a new service is registered/deregistered, ZooKeeper notifies the client via a watch event and the client can read the list of services. Even though this looks trivial,
+there are lot of things one needs to keep in mind like ensuring that you first set the watch back on ZooKeeper before reading data.
+
+
+### Poll
+
+Another approach is for the client to periodically read the ZooKeeper path and get the list of services.
+
+Both approaches have pros and cons, for example setting a watch might trigger herd effect if there are large number of clients. This is problematic, especially when servers are starting up.
+But the advantage to setting watches is that clients are immediately notified of a change which is not true in case of polling.
+In some cases, having both watches and polls makes sense; watch allows one to get notifications as soon as possible while poll provides a safety net if a watch event is missed because of code bug or ZooKeeper fails to notify.
+
+### Other Developer Considerations
+* What happens when the ZooKeeper session expires? All the watches and ephemeral nodes previously added or created by this server are lost. One needs to add the watches again, recreate the ephemeral nodes, and so on.
+* Due to network issues or Java GC pauses session expiry might happen again and again; this phenomenon is known as flapping. It\'s important for the server to detect this and deregister itself.
+
+### Other Operational Considerations
+* What if the node is behaving badly? One might kill the server, but it will lose the ability to debug. It would be nice to have the ability to mark a server as disabled and clients know that a node is disabled and will not contact that node.
+
+### Configuration Ownership
+
+This is an important aspect that is often ignored in the initial stages of your development. Typically, the service discovery pattern means that servers start up with some configuration which it simply puts into ZooKeeper. While this works well in the beginning, configuration management becomes very difficult since the servers themselves are statically configured. Any change in server configuration implies restarting the server. Ideally, it will be nice to have the ability to change configuration dynamically without having to restart a server.
+
+Ideally you want a hybrid solution, a node starts with minimal configuration and gets the rest of configuration from ZooKeeper.
+
+### Using Helix for Service Discovery
+
+Even though Helix has a higher-level abstraction in terms of state machines, constraints and objectives, service discovery is one of things has been a prevalent use case from the start.
+The controller uses the exact mechanism we described above to discover when new servers join the cluster. We create these ZNodes under /CLUSTERNAME/LIVEINSTANCES.
+Since at any time there is only one controller, we use a ZK watch to track the liveness of a server.
+
+This recipe simply demonstrates how one can re-use that part for implementing service discovery. This demonstrates multiple modes of service discovery:
+
+* POLL: The client reads from zookeeper at regular intervals 30 seconds. Use this if you have 100's of clients
+* WATCH: The client sets up watcher and gets notified of the changes. Use this if you have 10's of clients
+* NONE: This does neither of the above, but reads directly from zookeeper when ever needed
+
+Helix provides these additional features compared to other implementations available elsewhere:
+
+* It has the concept of disabling a node which means that a badly behaving node can be disabled using the Helix admin API
+* It automatically detects if a node connects/disconnects from zookeeper repeatedly and disables the node
+* Configuration management
+ * Allows one to set configuration via the admin API at various granulaties like cluster, instance, resource, partition
+ * Configurations can be dynamically changed
+ * The server is notified when configurations change
+
+
+### Checkout and Build
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+mvn clean install package -DskipTests
+cd recipes/service-discovery/target/service-discovery-pkg/bin
+chmod +x *
+```
+
+### Start ZooKeeper
+
+```
+./start-standalone-zookeeper 2199
+```
+
+### Run the Demo
+
+```
+./service-discovery-demo.sh
+```
+
+### Output
+
+```
+START:Service discovery demo mode:WATCH
+ Registering service
+ host.x.y.z_12000
+ host.x.y.z_12001
+ host.x.y.z_12002
+ host.x.y.z_12003
+ host.x.y.z_12004
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12000
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12002
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Deregistering service:
+ host.x.y.z_12002
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12000
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Registering service:host.x.y.z_12002
+END:Service discovery demo mode:WATCH
+=============================================
+START:Service discovery demo mode:POLL
+ Registering service
+ host.x.y.z_12000
+ host.x.y.z_12001
+ host.x.y.z_12002
+ host.x.y.z_12003
+ host.x.y.z_12004
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12000
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12002
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Deregistering service:
+ host.x.y.z_12002
+ Sleeping for poll interval:30000
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12000
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Registering service:host.x.y.z_12002
+END:Service discovery demo mode:POLL
+=============================================
+START:Service discovery demo mode:NONE
+ Registering service
+ host.x.y.z_12000
+ host.x.y.z_12001
+ host.x.y.z_12002
+ host.x.y.z_12003
+ host.x.y.z_12004
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12000
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12002
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Deregistering service:
+ host.x.y.z_12000
+ SERVICES AVAILABLE
+ SERVICENAME HOST PORT
+ myServiceName host.x.y.z 12001
+ myServiceName host.x.y.z 12002
+ myServiceName host.x.y.z 12003
+ myServiceName host.x.y.z 12004
+ Registering service:host.x.y.z_12000
+END:Service discovery demo mode:NONE
+=============================================
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/recipes/task_dag_execution.md
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@@ -0,0 +1,199 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Distributed Task Execution
+--------------------------
+
+This recipe is intended to demonstrate how task dependencies can be modeled using primitives provided by Helix. A given task can be run with the desired amount of parallelism and will start only when upstream dependencies are met. The demo executes the task DAG described below using 10 workers. Although the demo starts the workers as threads, there is no requirement that all the workers need to run in the same process. In reality, these workers run on many different boxes on a cluster. When worker fails, Helix takes care of re-assigning a failed task partition to a new worker.
+
+Redis is used as a result store. Any other suitable implementation for TaskResultStore can be plugged in.
+
+### Workflow
+
+#### Input
+
+10000 impression events and around 100 click events are pre-populated in task result store (redis).
+
+* **ImpEvent**: format: id,isFraudulent,country,gender
+
+* **ClickEvent**: format: id,isFraudulent,impEventId
+
+#### Stages
+
++ **FilterImps**: Filters impression where isFraudulent=true.
+
++ **FilterClicks**: Filters clicks where isFraudulent=true
+
++ **impCountsByGender**: Generates impression counts grouped by gender. It does this by incrementing the count for 'impression_gender_counts:<gender_value>' in the task result store (redis hash). Depends on: **FilterImps**
+
++ **impCountsByCountry**: Generates impression counts grouped by country. It does this by incrementing the count for 'impression_country_counts:<country_value>' in the task result store (redis hash). Depends on: **FilterClicks**
+
++ **impClickJoin**: Joins clicks with corresponding impression event using impEventId as the join key. Join is needed to pull dimensions not present in click event. Depends on: **FilterImps, FilterClicks**
+
++ **clickCountsByGender**: Generates click counts grouped by gender. It does this by incrementing the count for click_gender_counts:<gender_value> in the task result store (redis hash). Depends on: **impClickJoin**
+
++ **clickCountsByGender**: Generates click counts grouped by country. It does this by incrementing the count for click_country_counts:<country_value> in the task result store (redis hash). Depends on: **impClickJoin**
+
++ **report**: Reads from all aggregates generated by previous stages and prints them. Depends on: **impCountsByGender, impCountsByCountry, clickCountsByGender,clickCountsByGender**
+
+
+### Creating a DAG
+
+Each stage is represented as a Node along with the upstream dependency and desired parallelism. Each stage is modeled as a resource in Helix using OnlineOffline state model. As part of an Offline to Online transition, we watch the external view of upstream resources and wait for them to transition to the online state. See Task.java for additional info.
+
+```
+Dag dag = new Dag();
+dag.addNode(new Node("filterImps", 10, ""));
+dag.addNode(new Node("filterClicks", 5, ""));
+dag.addNode(new Node("impClickJoin", 10, "filterImps,filterClicks"));
+dag.addNode(new Node("impCountsByGender", 10, "filterImps"));
+dag.addNode(new Node("impCountsByCountry", 10, "filterImps"));
+dag.addNode(new Node("clickCountsByGender", 5, "impClickJoin"));
+dag.addNode(new Node("clickCountsByCountry", 5, "impClickJoin"));
+dag.addNode(new Node("report",1,"impCountsByGender,impCountsByCountry,clickCountsByGender,clickCountsByCountry"));
+```
+
+### Demo
+
+In order to run the demo, use the following steps
+
+See http://redis.io/topics/quickstart on how to install redis server
+
+```
+Start redis e.g:
+./redis-server --port 6379
+
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout helix-0.6.8
+cd recipes/task-execution
+mvn clean install package -DskipTests
+cd target/task-execution-pkg/bin
+chmod +x task-execution-demo.sh
+./task-execution-demo.sh 2181 localhost 6379
+
+```
+
+Here\'s a visual representation of the DAG.
+
+```
+
+
+
+
+
+ +-----------------+ +----------------+
+ | filterImps | | filterClicks |
+ | (parallelism=10)| | (parallelism=5)|
+ +----------+-----++ +-------+--------+
+ | | | |
+ | | | |
+ | | | |
+ | | +------->--------v------------+
+ +--------------<-+ +------v-------+ | impClickJoin |
+ |impCountsByGender |impCountsByCountry | (parallelism=10) |
+ |(parallelism=10) |(parallelism=10) ++-------------------+-+
+ +-----------+--+ +---+----------+ | |
+ | | | |
+ | | | |
+ | | +--------v---------+ +-v-------------------+
+ | | |clickCountsByGender |clickCountsByCountry |
+ | | |(parallelism=5) | |(parallelism=5) |
+ | | +----+-------------+ +---------------------+
+ | | | |
+ | | | |
+ | | | |
+ +----->+-----+>-----------v----+<---------------+
+ | report |
+ |(parallelism=1) |
+ +-----------------------+
+
+```
+
+(credit for above ascii art: http://www.asciiflow.com)
+
+#### Output
+
+```
+Done populating dummy data
+Executing filter task for filterImps_3 for impressions_demo
+Executing filter task for filterImps_2 for impressions_demo
+Executing filter task for filterImps_0 for impressions_demo
+Executing filter task for filterImps_1 for impressions_demo
+Executing filter task for filterImps_4 for impressions_demo
+Executing filter task for filterClicks_3 for clicks_demo
+Executing filter task for filterClicks_1 for clicks_demo
+Executing filter task for filterImps_8 for impressions_demo
+Executing filter task for filterImps_6 for impressions_demo
+Executing filter task for filterClicks_2 for clicks_demo
+Executing filter task for filterClicks_0 for clicks_demo
+Executing filter task for filterImps_7 for impressions_demo
+Executing filter task for filterImps_5 for impressions_demo
+Executing filter task for filterClicks_4 for clicks_demo
+Executing filter task for filterImps_9 for impressions_demo
+Running AggTask for impCountsByGender_3 for filtered_impressions_demo gender
+Running AggTask for impCountsByGender_2 for filtered_impressions_demo gender
+Running AggTask for impCountsByGender_0 for filtered_impressions_demo gender
+Running AggTask for impCountsByGender_9 for filtered_impressions_demo gender
+Running AggTask for impCountsByGender_1 for filtered_impressions_demo gender
+Running AggTask for impCountsByGender_4 for filtered_impressions_demo gender
+Running AggTask for impCountsByCountry_4 for filtered_impressions_demo country
+Running AggTask for impCountsByGender_5 for filtered_impressions_demo gender
+Executing JoinTask for impClickJoin_2
+Running AggTask for impCountsByCountry_3 for filtered_impressions_demo country
+Running AggTask for impCountsByCountry_1 for filtered_impressions_demo country
+Running AggTask for impCountsByCountry_0 for filtered_impressions_demo country
+Running AggTask for impCountsByCountry_2 for filtered_impressions_demo country
+Running AggTask for impCountsByGender_6 for filtered_impressions_demo gender
+Executing JoinTask for impClickJoin_1
+Executing JoinTask for impClickJoin_0
+Executing JoinTask for impClickJoin_3
+Running AggTask for impCountsByGender_8 for filtered_impressions_demo gender
+Executing JoinTask for impClickJoin_4
+Running AggTask for impCountsByGender_7 for filtered_impressions_demo gender
+Running AggTask for impCountsByCountry_5 for filtered_impressions_demo country
+Running AggTask for impCountsByCountry_6 for filtered_impressions_demo country
+Executing JoinTask for impClickJoin_9
+Running AggTask for impCountsByCountry_8 for filtered_impressions_demo country
+Running AggTask for impCountsByCountry_7 for filtered_impressions_demo country
+Executing JoinTask for impClickJoin_5
+Executing JoinTask for impClickJoin_6
+Running AggTask for impCountsByCountry_9 for filtered_impressions_demo country
+Executing JoinTask for impClickJoin_8
+Executing JoinTask for impClickJoin_7
+Running AggTask for clickCountsByCountry_1 for joined_clicks_demo country
+Running AggTask for clickCountsByCountry_0 for joined_clicks_demo country
+Running AggTask for clickCountsByCountry_2 for joined_clicks_demo country
+Running AggTask for clickCountsByCountry_3 for joined_clicks_demo country
+Running AggTask for clickCountsByGender_1 for joined_clicks_demo gender
+Running AggTask for clickCountsByCountry_4 for joined_clicks_demo country
+Running AggTask for clickCountsByGender_3 for joined_clicks_demo gender
+Running AggTask for clickCountsByGender_2 for joined_clicks_demo gender
+Running AggTask for clickCountsByGender_4 for joined_clicks_demo gender
+Running AggTask for clickCountsByGender_0 for joined_clicks_demo gender
+Running reports task
+Impression counts per country
+{CANADA=1940, US=1958, CHINA=2014, UNKNOWN=2022, UK=1946}
+Click counts per country
+{US=24, CANADA=14, CHINA=26, UNKNOWN=14, UK=22}
+Impression counts per gender
+{F=3325, UNKNOWN=3259, M=3296}
+Click counts per gender
+{F=33, UNKNOWN=32, M=35}
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_admin.md
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+++ b/website/0.6.8/src/site/markdown/tutorial_admin.md
@@ -0,0 +1,408 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Admin Operations</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Admin Operations
+
+Helix provides a set of admin APIs for cluster management operations. They are supported via:
+
+* Java API
+* Command Line Interface
+* REST Interface via helix-admin-webapp
+
+### Java API
+See interface [_org.apache.helix.HelixAdmin_](http://helix.apache.org/javadocs/0.6.8/reference/org/apache/helix/HelixAdmin.html)
+
+### Command Line Interface
+The command line tool comes with helix-core package:
+
+Get the command line tool:
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+./build
+cd helix-core/target/helix-core-pkg/bin
+chmod +x *.sh
+```
+
+Get help:
+
+```
+./helix-admin.sh --help
+```
+
+All other commands have this form:
+
+```
+./helix-admin.sh --zkSvr <ZookeeperServerAddress> <command> <parameters>
+```
+
+#### Supported Commands
+
+| Command Syntax | Description |
+| -------------- | ----------- |
+| _\-\-activateCluster \<clusterName controllerCluster true/false\>_ | Enable/disable a cluster in distributed controller mode |
+| _\-\-addCluster \<clusterName\>_ | Add a new cluster |
+| _\-\-addIdealState \<clusterName resourceName fileName.json\>_ | Add an ideal state to a cluster |
+| _\-\-addInstanceTag \<clusterName instanceName tag\>_ | Add a tag to an instance |
+| _\-\-addNode \<clusterName instanceId\>_ | Add an instance to a cluster |
+| _\-\-addResource \<clusterName resourceName partitionNumber stateModelName\>_ | Add a new resource to a cluster |
+| _\-\-addResourceProperty \<clusterName resourceName propertyName propertyValue\>_ | Add a resource property |
+| _\-\-addStateModelDef \<clusterName fileName.json\>_ | Add a State model definition to a cluster |
+| _\-\-dropCluster \<clusterName\>_ | Delete a cluster |
+| _\-\-dropNode \<clusterName instanceId\>_ | Remove a node from a cluster |
+| _\-\-dropResource \<clusterName resourceName\>_ | Remove an existing resource from a cluster |
+| _\-\-enableCluster \<clusterName true/false\>_ | Enable/disable a cluster |
+| _\-\-enableInstance \<clusterName instanceId true/false\>_ | Enable/disable an instance |
+| _\-\-enablePartition \<true/false clusterName nodeId resourceName partitionName\>_ | Enable/disable a partition |
+| _\-\-getConfig \<configScope configScopeArgs configKeys\>_ | Get user configs |
+| _\-\-getConstraints \<clusterName constraintType\>_ | Get constraints |
+| _\-\-help_ | print help information |
+| _\-\-instanceGroupTag \<instanceTag\>_ | Specify instance group tag, used with rebalance command |
+| _\-\-listClusterInfo \<clusterName\>_ | Show information of a cluster |
+| _\-\-listClusters_ | List all clusters |
+| _\-\-listInstanceInfo \<clusterName instanceId\>_ | Show information of an instance |
+| _\-\-listInstances \<clusterName\>_ | List all instances in a cluster |
+| _\-\-listPartitionInfo \<clusterName resourceName partitionName\>_ | Show information of a partition |
+| _\-\-listResourceInfo \<clusterName resourceName\>_ | Show information of a resource |
+| _\-\-listResources \<clusterName\>_ | List all resources in a cluster |
+| _\-\-listStateModel \<clusterName stateModelName\>_ | Show information of a state model |
+| _\-\-listStateModels \<clusterName\>_ | List all state models in a cluster |
+| _\-\-maxPartitionsPerNode \<maxPartitionsPerNode\>_ | Specify the max partitions per instance, used with addResourceGroup command |
+| _\-\-rebalance \<clusterName resourceName replicas\>_ | Rebalance a resource |
+| _\-\-removeConfig \<configScope configScopeArgs configKeys\>_ | Remove user configs |
+| _\-\-removeConstraint \<clusterName constraintType constraintId\>_ | Remove a constraint |
+| _\-\-removeInstanceTag \<clusterName instanceId tag\>_ | Remove a tag from an instance |
+| _\-\-removeResourceProperty \<clusterName resourceName propertyName\>_ | Remove a resource property |
+| _\-\-resetInstance \<clusterName instanceId\>_ | Reset all erroneous partitions on an instance |
+| _\-\-resetPartition \<clusterName instanceId resourceName partitionName\>_ | Reset an erroneous partition |
+| _\-\-resetResource \<clusterName resourceName\>_ | Reset all erroneous partitions of a resource |
+| _\-\-setConfig \<configScope configScopeArgs configKeyValueMap\>_ | Set user configs |
+| _\-\-setConstraint \<clusterName constraintType constraintId constraintKeyValueMap\>_ | Set a constraint |
+| _\-\-swapInstance \<clusterName oldInstance newInstance\>_ | Swap an old instance with a new instance |
+| _\-\-zkSvr \<ZookeeperServerAddress\>_ | Provide zookeeper address |
+
+### REST Interface
+
+The REST interface comes wit helix-admin-webapp package:
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+./build
+cd helix-admin-webapp/target/helix-admin-webapp-pkg/bin
+chmod +x *.sh
+./run-rest-admin.sh --zkSvr <zookeeperAddress> --port <port> // make sure ZooKeeper is running
+```
+
+#### URL and support methods
+
+* _/clusters_
+ * List all clusters
+
+ ```
+ curl http://localhost:8100/clusters
+ ```
+
+ * Add a cluster
+
+ ```
+ curl -d 'jsonParameters={"command":"addCluster","clusterName":"MyCluster"}' -H "Content-Type: application/json" http://localhost:8100/clusters
+ ```
+
+* _/clusters/{clusterName}_
+ * List cluster information
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster
+ ```
+
+ * Enable/disable a cluster in distributed controller mode
+
+ ```
+ curl -d 'jsonParameters={"command":"activateCluster","grandCluster":"MyControllerCluster","enabled":"true"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster
+ ```
+
+ * Remove a cluster
+
+ ```
+ curl -X DELETE http://localhost:8100/clusters/MyCluster
+ ```
+
+* _/clusters/{clusterName}/resourceGroups_
+ * List all resources in a cluster
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/resourceGroups
+ ```
+
+ * Add a resource to cluster
+
+ ```
+ curl -d 'jsonParameters={"command":"addResource","resourceGroupName":"MyDB","partitions":"8","stateModelDefRef":"MasterSlave" }' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/resourceGroups
+ ```
+
+* _/clusters/{clusterName}/resourceGroups/{resourceName}_
+ * List resource information
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB
+ ```
+
+ * Drop a resource
+
+ ```
+ curl -X DELETE http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB
+ ```
+
+ * Reset all erroneous partitions of a resource
+
+ ```
+ curl -d 'jsonParameters={"command":"resetResource"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB
+ ```
+
+* _/clusters/{clusterName}/resourceGroups/{resourceName}/idealState_
+ * Rebalance a resource
+
+ ```
+ curl -d 'jsonParameters={"command":"rebalance","replicas":"3"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB/idealState
+ ```
+
+ * Add an ideal state
+
+ ```
+ echo jsonParameters={
+ "command":"addIdealState"
+ }&newIdealState={
+ "id" : "MyDB",
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO",
+ "NUM_PARTITIONS" : "8",
+ "REBALANCE_MODE" : "SEMI_AUTO",
+ "REPLICAS" : "0",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ "STATE_MODEL_FACTORY_NAME" : "DEFAULT"
+ },
+ "listFields" : {
+ },
+ "mapFields" : {
+ "MyDB_0" : {
+ "localhost_1001" : "MASTER",
+ "localhost_1002" : "SLAVE"
+ }
+ }
+ }
+ > newIdealState.json
+ curl -d @'./newIdealState.json' -H 'Content-Type: application/json' http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB/idealState
+ ```
+
+ * Add resource property
+
+ ```
+ curl -d 'jsonParameters={"command":"addResourceProperty","REBALANCE_TIMER_PERIOD":"500"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB/idealState
+ ```
+
+* _/clusters/{clusterName}/resourceGroups/{resourceName}/externalView_
+ * Show resource external view
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB/externalView
+ ```
+* _/clusters/{clusterName}/instances_
+ * List all instances
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/instances
+ ```
+
+ * Add an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"addInstance","instanceNames":"localhost_1001"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances
+ ```
+
+ * Swap an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"swapInstance","oldInstance":"localhost_1001", "newInstance":"localhost_1002"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances
+ ```
+* _/clusters/{clusterName}/instances/{instanceName}_
+ * Show instance information
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+ * Enable/disable an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"enableInstance","enabled":"false"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+ * Drop an instance
+
+ ```
+ curl -X DELETE http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+ * Disable/enable partitions on an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"enablePartition","resource": "MyDB","partition":"MyDB_0", "enabled" : "false"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+ * Reset an erroneous partition on an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"resetPartition","resource": "MyDB","partition":"MyDB_0"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+ * Reset all erroneous partitions on an instance
+
+ ```
+ curl -d 'jsonParameters={"command":"resetInstance"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/instances/localhost_1001
+ ```
+
+* _/clusters/{clusterName}/configs_
+ * Get user cluster level config
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/configs/cluster
+ ```
+
+ * Set user cluster level config
+
+ ```
+ curl -d 'jsonParameters={"command":"setConfig","configs":"key1=value1,key2=value2"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/configs/cluster
+ ```
+
+ * Remove user cluster level config
+
+ ```
+ curl -d 'jsonParameters={"command":"removeConfig","configs":"key1,key2"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/configs/cluster
+ ```
+
+ * Get/set/remove user participant level config
+
+ ```
+ curl -d 'jsonParameters={"command":"setConfig","configs":"key1=value1,key2=value2"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/configs/participant/localhost_1001
+ ```
+
+ * Get/set/remove resource level config
+
+ ```
+ curl -d 'jsonParameters={"command":"setConfig","configs":"key1=value1,key2=value2"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/configs/resource/MyDB
+ ```
+
+* _/clusters/{clusterName}/controller_
+ * Show controller information
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/Controller
+ ```
+
+ * Enable/disable cluster
+
+ ```
+ curl -d 'jsonParameters={"command":"enableCluster","enabled":"false"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/Controller
+ ```
+
+* _/zkPath/{path}_
+ * Get information for zookeeper path
+
+ ```
+ curl http://localhost:8100/zkPath/MyCluster
+ ```
+
+* _/clusters/{clusterName}/StateModelDefs_
+ * Show all state model definitions
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/StateModelDefs
+ ```
+
+ * Add a state mdoel definition
+
+ ```
+ echo jsonParameters={
+ "command":"addStateModelDef"
+ }&newStateModelDef={
+ "id" : "OnlineOffline",
+ "simpleFields" : {
+ "INITIAL_STATE" : "OFFLINE"
+ },
+ "listFields" : {
+ "STATE_PRIORITY_LIST" : [ "ONLINE", "OFFLINE", "DROPPED" ],
+ "STATE_TRANSITION_PRIORITYLIST" : [ "OFFLINE-ONLINE", "ONLINE-OFFLINE", "OFFLINE-DROPPED" ]
+ },
+ "mapFields" : {
+ "DROPPED.meta" : {
+ "count" : "-1"
+ },
+ "OFFLINE.meta" : {
+ "count" : "-1"
+ },
+ "OFFLINE.next" : {
+ "DROPPED" : "DROPPED",
+ "ONLINE" : "ONLINE"
+ },
+ "ONLINE.meta" : {
+ "count" : "R"
+ },
+ "ONLINE.next" : {
+ "DROPPED" : "OFFLINE",
+ "OFFLINE" : "OFFLINE"
+ }
+ }
+ }
+ > newStateModelDef.json
+ curl -d @'./untitled.txt' -H 'Content-Type: application/json' http://localhost:8100/clusters/MyCluster/StateModelDefs
+ ```
+
+* _/clusters/{clusterName}/StateModelDefs/{stateModelDefName}_
+ * Show a state model definition
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/StateModelDefs/OnlineOffline
+ ```
+
+* _/clusters/{clusterName}/constraints/{constraintType}_
+ * Show all contraints
+
+ ```
+ curl http://localhost:8100/clusters/MyCluster/constraints/MESSAGE_CONSTRAINT
+ ```
+
+ * Set a contraint
+
+ ```
+ curl -d 'jsonParameters={"constraintAttributes":"RESOURCE=MyDB,CONSTRAINT_VALUE=1"}' -H "Content-Type: application/json" http://localhost:8100/clusters/MyCluster/constraints/MESSAGE_CONSTRAINT/MyConstraint
+ ```
+
+ * Remove a constraint
+
+ ```
+ curl -X DELETE http://localhost:8100/clusters/MyCluster/constraints/MESSAGE_CONSTRAINT/MyConstraint
+ ```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_agent.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Helix Agent</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Helix Agent (for non-JVM systems)
+
+Not every distributed system is written on the JVM, but many systems would benefit from the cluster management features that Helix provides. To make a non-JVM system work with Helix, you can use the Helix Agent module.
+
+### What is Helix Agent?
+
+Helix is built on the following assumption: if your distributed resource is modeled by a finite state machine, then Helix can tell participants when they should transition between states. In the Java API, this means implementing transition callbacks. In the Helix agent API, this means providing commands than can run for each transition.
+
+These commands could do anything behind the scenes; Helix only requires that they exit once the state transition is complete.
+
+### Configuring Transition Commands
+
+Here's how to tell Helix which commands to run on state transitions:
+
+#### Java
+
+Using the Java API, first get a configuration scope (the Helix agent supports both cluster and resource scopes, picking resource first if it is available):
+
+```
+// Cluster scope
+HelixConfigScope scope =
+ new HelixConfigScopeBuilder(ConfigScopeProperty.CLUSTER).forCluster(clusterName).build();
+
+// Resource scope
+HelixConfigScope scope =
+ new HelixConfigScopeBuilder(ConfigScopeProperty.RESOURCE).forCluster(clusterName).forResource(resourceName).build();
+```
+
+Then, specify the command to run for each state transition:
+
+```
+// Get the configuration accessor
+ConfigAccessor configAccessor = new ConfigAccessor(_gZkClient);
+
+// Specify the script for OFFLINE --> ONLINE
+CommandConfig.Builder builder = new CommandConfig.Builder();
+CommandConfig cmdConfig =
+ builder.setTransition("OFFLINE", "ONLINE").setCommand("simpleHttpClient.py OFFLINE-ONLINE")
+ .setCommandWorkingDir(workingDir)
+ .setCommandTimeout("5000L") // optional: ms to wait before failing
+ .setPidFile(pidFile) // optional: for daemon-like systems that will write the process id to a file
+ .build();
+configAccessor.set(scope, cmdConfig.toKeyValueMap());
+
+// Specify the script for ONLINE --> OFFLINE
+builder = new CommandConfig.Builder();
+cmdConfig =
+ builder.setTransition("ONLINE", "OFFLINE").setCommand("simpleHttpClient.py ONLINE-OFFLINE")
+ .setCommandWorkingDir(workingDir)
+ .build();
+configAccessor.set(scope, cmdConfig.toKeyValueMap());
+
+// Specify NOP for OFFLINE --> DROPPED
+builder = new CommandConfig.Builder();
+cmdConfig =
+ builder.setTransition("OFFLINE", "DROPPED")
+ .setCommand(CommandAttribute.NOP.getName())
+ .build();
+configAccessor.set(scope, cmdConfig.toKeyValueMap());
+```
+
+In this example, we have a program called simpleHttpClient.py that we call for all transitions, only changing the arguments that are passed in. However, there is no requirement that each transition invoke the same program; this API allows running arbitrary commands in arbitrary directories with arbitrary arguments.
+
+Notice that that for the OFFLINE \-\-\> DROPPED transition, we do not run any command (specifically, we specify the NOP command). This just tells Helix that the system doesn't care about when things are dropped, and it can consider the transition already done.
+
+#### Command Line
+
+It is also possible to configure everything directly from the command line. Here's how that would look for cluster-wide configuration:
+
+```
+# Specify the script for OFFLINE --> ONLINE
+/helix-admin.sh --zkSvr localhost:2181 --setConfig CLUSTER clusterName OFFLINE-ONLINE.command="simpleHttpClient.py OFFLINE-ONLINE",OFFLINE-ONLINE.workingDir="/path/to/script", OFFLINE-ONLINE.command.pidfile="/path/to/pidfile"
+
+# Specify the script for ONLINE --> OFFLINE
+/helix-admin.sh --zkSvr localhost:2181 --setConfig CLUSTER clusterName ONLINE-OFFLINE.command="simpleHttpClient.py ONLINE-OFFLINE",ONLINE-OFFLINE.workingDir="/path/to/script", OFFLINE-ONLINE.command.pidfile="/path/to/pidfile"
+
+# Specify NOP for OFFLINE --> DROPPED
+/helix-admin.sh --zkSvr localhost:2181 --setConfig CLUSTER clusterName ONLINE-OFFLINE.command="nop"
+```
+
+Like in the Java configuration, it is also possible to specify a resource scope instead of a cluster scope:
+
+```
+# Specify the script for OFFLINE --> ONLINE
+/helix-admin.sh --zkSvr localhost:2181 --setConfig RESOURCE clusterName,resourceName OFFLINE-ONLINE.command="simpleHttpClient.py OFFLINE-ONLINE",OFFLINE-ONLINE.workingDir="/path/to/script", OFFLINE-ONLINE.command.pidfile="/path/to/pidfile"
+```
+
+### Starting the Agent
+
+There should be an agent running for every participant you have running. Ideally, its lifecycle should match that of the participant. Here, we have a simple long-running participant called simpleHttpServer.py. Its only purpose is to record state transitions.
+
+Here are some ways that you can start the Helix agent:
+
+#### Java
+
+```
+// Start your application process
+ExternalCommand serverCmd = ExternalCommand.start(workingDir + "/simpleHttpServer.py");
+
+// Start the agent
+Thread agentThread = new Thread() {
+ @Override
+ public void run() {
+ while(!isInterrupted()) {
+ try {
+ HelixAgentMain.main(new String[] {
+ "--zkSvr", zkAddr, "--cluster", clusterName, "--instanceName", instanceName,
+ "--stateModel", "OnlineOffline"
+ });
+ } catch (InterruptedException e) {
+ LOG.info("Agent thread interrupted", e);
+ interrupt();
+ } catch (Exception e) {
+ LOG.error("Exception start helix-agent", e);
+ }
+ }
+ }
+};
+agentThread.start();
+
+// Wait for the process to terminate (either intentionally or unintentionally)
+serverCmd.waitFor();
+
+// Kill the agent
+agentThread.interrupt();
+```
+
+#### Command Line
+
+```
+# Build Helix and start the agent
+mvn clean install -DskipTests
+chmod +x helix-agent/target/helix-agent-pkg/bin/*
+helix-agent/target/helix-agent-pkg/bin/start-helix-agent.sh --zkSvr zkAddr1,zkAddr2 --cluster clusterName --instanceName instanceName --stateModel OnlineOffline
+
+# Here, you can define your own logic to terminate this agent when your process terminates
+...
+```
+
+### Example
+
+[Here](https://git-wip-us.apache.org/repos/asf?p=helix.git;a=blob;f=helix-agent/src/test/java/org/apache/helix/agent/TestHelixAgent.java;h=ccf64ce5544207c7e48261682ea69945b71da7f1;hb=refs/heads/master) is a basic system that uses the Helix agent package.
+
+### Notes
+
+As you may have noticed from the examples, the participant program and the state transition program are two different programs. The former is a _long-running_ process that is directly tied to the Helix agent. The latter is a process that only exists while a state transition is underway. Despite this, these two processes should be intertwined. The transition command will need to communicate to the participant to actually complete the state transition and the participant will need to communicate whether or not this was successful. The implementation of this protocol is the responsibility of the system.
\ No newline at end of file
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Controller</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Controller
+
+Next, let\'s implement the controller. This is the brain of the cluster. Helix makes sure there is exactly one active controller running the cluster.
+
+### Start a Connection
+
+The Helix manager requires the following parameters:
+
+* clusterName: A logical name to represent the group of nodes
+* instanceName: A logical name of the process creating the manager instance. Generally this is host:port
+* instanceType: Type of the process. This can be one of the following types, in this case use CONTROLLER:
+ * CONTROLLER: Process that controls the cluster, any number of controllers can be started but only one will be active at any given time
+ * PARTICIPANT: Process that performs the actual task in the distributed system
+ * SPECTATOR: Process that observes the changes in the cluster
+ * ADMIN: To carry out system admin actions
+* zkConnectString: Connection string to ZooKeeper. This is of the form host1:port1,host2:port2,host3:port3
+
+```
+manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ instanceType,
+ zkConnectString);
+```
+
+### Controller Code
+
+The Controller needs to know about all changes in the cluster. Helix takes care of this with the default implementation.
+If you need additional functionality, see GenericHelixController on how to configure the pipeline.
+
+```
+manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ InstanceType.CONTROLLER,
+ zkConnectString);
+manager.connect();
+```
+The snippet above shows how the controller is started. You can also start the controller using command line interface.
+
+```
+cd helix/helix-core/target/helix-core-pkg/bin
+./run-helix-controller.sh --zkSvr <Zookeeper ServerAddress (Required)> --cluster <Cluster name (Required)>
+```
+
+### Controller Deployment Modes
+
+Helix provides multiple options to deploy the controller.
+
+#### STANDALONE
+
+The Controller can be started as a separate process to manage a cluster. This is the recommended approach. However, since one controller can be a single point of failure, multiple controller processes are required for reliability. Even if multiple controllers are running, only one will be actively managing the cluster at any time and is decided by a leader-election process. If the leader fails, another leader will take over managing the cluster.
+
+Even though we recommend this method of deployment, it has the drawback of having to manage an additional service for each cluster. See the Controller as a Service option.
+
+#### EMBEDDED
+
+If setting up a separate controller process is not viable, then it is possible to embed the controller as a library in each of the participants.
+
+#### CONTROLLER AS A SERVICE
+
+One of the cool features we added in Helix was to use a set of controllers to manage a large number of clusters.
+
+For example if you have X clusters to be managed, instead of deploying X*3 (3 controllers for fault tolerance) controllers for each cluster, one can deploy just 3 controllers. Each controller can manage X/3 clusters. If any controller fails, the remaining two will manage X/2 clusters.
+
+Next, let\'s implement the controller. This is the brain of the cluster. Helix makes sure there is exactly one active controller running the cluster.
+
+### Start the Helix agent
+
+
+It requires the following parameters:
+
+* clusterName: A logical name to represent the group of nodes
+* instanceName: A logical name of the process creating the manager instance. Generally this is host:port.
+* instanceType: Type of the process. This can be one of the following types, in this case use CONTROLLER:
+ * CONTROLLER: Process that controls the cluster, any number of controllers can be started but only one will be active at any given time.
+ * PARTICIPANT: Process that performs the actual task in the distributed system.
+ * SPECTATOR: Process that observes the changes in the cluster.
+ * ADMIN: To carry out system admin actions.
+* zkConnectString: Connection string to Zookeeper. This is of the form host1:port1,host2:port2,host3:port3.
+
+```
+ manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ instanceType,
+ zkConnectString);
+```
+
+### Controller Code
+
+The Controller needs to know about all changes in the cluster. Helix takes care of this with the default implementation.
+If you need additional functionality, see GenericHelixController on how to configure the pipeline.
+
+```
+ manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ InstanceType.CONTROLLER,
+ zkConnectString);
+ manager.connect();
+ GenericHelixController controller = new GenericHelixController();
+ manager.addConfigChangeListener(controller);
+ manager.addLiveInstanceChangeListener(controller);
+ manager.addIdealStateChangeListener(controller);
+ manager.addExternalViewChangeListener(controller);
+ manager.addControllerListener(controller);
+```
+The snippet above shows how the controller is started. You can also start the controller using command line interface.
+
+```
+cd helix/helix-core/target/helix-core-pkg/bin
+./run-helix-controller.sh --zkSvr <Zookeeper ServerAddress (Required)> --cluster <Cluster name (Required)>
+```
+
+### Controller Deployment Modes
+
+Helix provides multiple options to deploy the controller.
+
+#### STANDALONE
+
+The Controller can be started as a separate process to manage a cluster. This is the recommended approach. However, since one controller can be a single point of failure, multiple controller processes are required for reliability. Even if multiple controllers are running, only one will be actively managing the cluster at any time and is decided by a leader-election process. If the leader fails, another leader will take over managing the cluster.
+
+Even though we recommend this method of deployment, it has the drawback of having to manage an additional service for each cluster. See Controller As a Service option.
+
+#### EMBEDDED
+
+If setting up a separate controller process is not viable, then it is possible to embed the controller as a library in each of the participants.
+
+#### CONTROLLER AS A SERVICE
+
+One of the cool features we added in Helix is to use a set of controllers to manage a large number of clusters.
+
+For example if you have X clusters to be managed, instead of deploying X*3 (3 controllers for fault tolerance) controllers for each cluster, one can deploy just 3 controllers. Each controller can manage X/3 clusters. If any controller fails, the remaining two will manage X/2 clusters.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_messaging.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Messaging</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Messaging
+
+In this chapter, we\'ll learn about messaging, a convenient feature in Helix for sending messages between nodes of a cluster. This is an interesting feature that is quite useful in practice. It is common that nodes in a distributed system require a mechanism to interact with each other.
+
+### Example: Bootstrapping a Replica
+
+Consider a search system where the index replica starts up and it does not have an index. A typical solution is to get the index from a common location, or to copy the index from another replica.
+
+Helix provides a messaging API for intra-cluster communication between nodes in the system. This API provides a mechanism to specify the message recipient in terms of resource, partition, and state rather than specifying hostnames. Helix ensures that the message is delivered to all of the required recipients. In this particular use case, the instance can specify the recipient criteria as all replicas of the desired partition to bootstrap.
+Since Helix is aware of the global state of the system, it can send the message to the appropriate nodes. Once the nodes respond, Helix provides the bootstrapping replica with all the responses.
+
+This is a very generic API and can also be used to schedule various periodic tasks in the cluster, such as data backups, log cleanup, etc.
+System Admins can also perform ad-hoc tasks, such as on-demand backups or a system command (such as rm -rf ;) across all nodes of the cluster
+
+```
+ClusterMessagingService messagingService = manager.getMessagingService();
+
+// Construct the Message
+Message requestBackupUriRequest = new Message(
+ MessageType.USER_DEFINE_MSG, UUID.randomUUID().toString());
+requestBackupUriRequest
+ .setMsgSubType(BootstrapProcess.REQUEST_BOOTSTRAP_URL);
+requestBackupUriRequest.setMsgState(MessageState.NEW);
+
+// Set the Recipient criteria: all nodes that satisfy the criteria will receive the message
+Criteria recipientCriteria = new Criteria();
+recipientCriteria.setInstanceName("%");
+recipientCriteria.setRecipientInstanceType(InstanceType.PARTICIPANT);
+recipientCriteria.setResource("MyDB");
+recipientCriteria.setPartition("");
+
+// Should be processed only by process(es) that are active at the time of sending the message
+// This means if the recipient is restarted after message is sent, it will not be processe.
+recipientCriteria.setSessionSpecific(true);
+
+// wait for 30 seconds
+int timeout = 30000;
+
+// the handler that will be invoked when any recipient responds to the message.
+BootstrapReplyHandler responseHandler = new BootstrapReplyHandler();
+
+// this will return only after all recipients respond or after timeout
+int sentMessageCount = messagingService.sendAndWait(recipientCriteria,
+ requestBackupUriRequest, responseHandler, timeout);
+```
+
+See HelixManager.DefaultMessagingService in the [Javadocs](http://helix.apache.org/javadocs/0.6.8/reference/org/apache/helix/messaging/DefaultMessagingService.html) for more information.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_participant.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Participant</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Participant
+
+In this chapter, we\'ll learn how to implement a __Participant__, which is a primary functional component of a distributed system.
+
+
+### Start a Connection
+
+The Helix manager is a common component that connects each system component with the controller.
+
+It requires the following parameters:
+
+* clusterName: A logical name to represent the group of nodes
+* instanceName: A logical name of the process creating the manager instance. Generally this is host:port
+* instanceType: Type of the process. This can be one of the following types, in this case, use PARTICIPANT
+ * CONTROLLER: Process that controls the cluster, any number of controllers can be started but only one will be active at any given time
+ * PARTICIPANT: Process that performs the actual task in the distributed system
+ * SPECTATOR: Process that observes the changes in the cluster
+ * ADMIN: To carry out system admin actions
+* zkConnectString: Connection string to ZooKeeper. This is of the form host1:port1,host2:port2,host3:port3
+
+After the Helix manager instance is created, the only thing that needs to be registered is the state model factory.
+The methods of the state model will be called when controller sends transitions to the participant. In this example, we'll use the OnlineOffline factory. Other options include:
+
+* MasterSlaveStateModelFactory
+* LeaderStandbyStateModelFactory
+* BootstrapHandler
+
+
+```
+manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ InstanceType.PARTICIPANT,
+ zkConnectString);
+StateMachineEngine stateMach = manager.getStateMachineEngine();
+
+//create a stateModelFactory that returns a statemodel object for each partition.
+stateModelFactory = new OnlineOfflineStateModelFactory();
+stateMach.registerStateModelFactory(stateModelType, stateModelFactory);
+manager.connect();
+```
+
+### Example State Model Factory
+
+Helix doesn\'t know what it means to change from OFFLINE\-\-\>ONLINE or ONLINE\-\-\>OFFLINE. The following code snippet shows where you insert your system logic for these two state transitions.
+
+```
+public class OnlineOfflineStateModelFactory extends
+ StateModelFactory<StateModel> {
+ @Override
+ public StateModel createNewStateModel(String stateUnitKey) {
+ OnlineOfflineStateModel stateModel = new OnlineOfflineStateModel();
+ return stateModel;
+ }
+ @StateModelInfo(states = "{'OFFLINE','ONLINE'}", initialState = "OFFINE")
+ public static class OnlineOfflineStateModel extends StateModel {
+ @Transition(from = "OFFLINE", to = "ONLINE")
+ public void onBecomeOnlineFromOffline(Message message,
+ NotificationContext context) {
+ System.out.println("OnlineOfflineStateModel.onBecomeOnlineFromOffline()");
+
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ // Application logic to handle transition //
+ // For example, you might start a service, run initialization, etc //
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ }
+
+ @Transition(from = "ONLINE", to = "OFFLINE")
+ public void onBecomeOfflineFromOnline(Message message,
+ NotificationContext context) {
+ System.out.println("OnlineOfflineStateModel.onBecomeOfflineFromOnline()");
+
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ // Application logic to handle transition //
+ // For example, you might shutdown a service, log this event, or change monitoring settings //
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ }
+ }
+}
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_propstore.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Application Property Store</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Application Property Store
+
+In this chapter, we\'ll learn how to use the application property store.
+
+### Property Store
+
+It is common that an application needs support for distributed, shared data structures. Helix uses ZooKeeper to store the application data and hence provides notifications when the data changes.
+
+While you could use ZooKeeper directly, Helix supports caching the data with a write-through cache. This is far more efficient than reading from ZooKeeper for every access.
+
+See [HelixManager.getHelixPropertyStore](http://helix.apache.org/javadocs/0.6.8/reference/org/apache/helix/store/package-summary.html) for details.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_rebalance.md
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/markdown/tutorial_rebalance.md b/website/0.6.8/src/site/markdown/tutorial_rebalance.md
new file mode 100644
index 0000000..2e1a79b
--- /dev/null
+++ b/website/0.6.8/src/site/markdown/tutorial_rebalance.md
@@ -0,0 +1,181 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Rebalancing Algorithms</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Rebalancing Algorithms
+
+The placement of partitions in a distributed system is essential for the reliability and scalability of the system. For example, when a node fails, it is important that the partitions hosted on that node are reallocated evenly among the remaining nodes. Consistent hashing is one such algorithm that can satisfy this guarantee. Helix provides a variant of consistent hashing based on the RUSH algorithm, among others.
+
+This means given a number of partitions, replicas and number of nodes, Helix does the automatic assignment of partition to nodes such that:
+
+* Each node has the same number of partitions
+* Replicas of the same partition do not stay on the same node
+* When a node fails, the partitions will be equally distributed among the remaining nodes
+* When new nodes are added, the number of partitions moved will be minimized along with satisfying the above criteria
+
+Helix employs a rebalancing algorithm to compute the _ideal state_ of the system. When the _current state_ differs from the _ideal state_, Helix uses it as the target state of the system and computes the appropriate transitions needed to bring it to the _ideal state_.
+
+Helix makes it easy to perform this operation, while giving you control over the algorithm. In this section, we\'ll see how to implement the desired behavior.
+
+Helix has four options for rebalancing, in increasing order of customization by the system builder:
+
+* FULL_AUTO
+* SEMI_AUTO
+* CUSTOMIZED
+* USER_DEFINED
+
+```
+ |FULL_AUTO | SEMI_AUTO | CUSTOMIZED| USER_DEFINED |
+ ---------------------------------------------------------|
+ LOCATION | HELIX | APP | APP | APP |
+ ---------------------------------------------------------|
+ STATE | HELIX | HELIX | APP | APP |
+ ----------------------------------------------------------
+```
+
+
+### FULL_AUTO
+
+When the rebalance mode is set to FULL_AUTO, Helix controls both the location of the replica along with the state. This option is useful for applications where creation of a replica is not expensive.
+
+For example, consider this system that uses a MasterSlave state model, with 3 partitions and 2 replicas in the ideal state.
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "REBALANCE_MODE" : "FULL_AUTO",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ }
+ "listFields" : {
+ "MyResource_0" : [],
+ "MyResource_1" : [],
+ "MyResource_2" : []
+ },
+ "mapFields" : {
+ }
+}
+```
+
+If there are 3 nodes in the cluster, then Helix will balance the masters and slaves equally. The ideal state is therefore:
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ },
+ "mapFields" : {
+ "MyResource_0" : {
+ "N1" : "MASTER",
+ "N2" : "SLAVE",
+ },
+ "MyResource_1" : {
+ "N2" : "MASTER",
+ "N3" : "SLAVE",
+ },
+ "MyResource_2" : {
+ "N3" : "MASTER",
+ "N1" : "SLAVE",
+ }
+ }
+}
+```
+
+Another typical example is evenly distributing a group of tasks among the currently healthy processes. For example, if there are 60 tasks and 4 nodes, Helix assigns 15 tasks to each node.
+When one node fails, Helix redistributes its 15 tasks to the remaining 3 nodes, resulting in a balanced 20 tasks per node. Similarly, if a node is added, Helix re-allocates 3 tasks from each of the 4 nodes to the 5th node, resulting in a balanced distribution of 12 tasks per node..
+
+### SEMI_AUTO
+
+When the application needs to control the placement of the replicas, use the SEMI_AUTO rebalance mode.
+
+Example: In the ideal state below, the partition \'MyResource_0\' is constrained to be placed only on node1 or node2. The choice of _state_ is still controlled by Helix. That means MyResource_0.MASTER could be on node1 and MyResource_0.SLAVE on node2, or vice-versa but neither would be placed on node3.
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "REBALANCE_MODE" : "SEMI_AUTO",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ }
+ "listFields" : {
+ "MyResource_0" : [node1, node2],
+ "MyResource_1" : [node2, node3],
+ "MyResource_2" : [node3, node1]
+ },
+ "mapFields" : {
+ }
+}
+```
+
+The MasterSlave state model requires that a partition has exactly one MASTER at all times, and the other replicas should be SLAVEs. In this simple example with 2 replicas per partition, there would be one MASTER and one SLAVE. Upon failover, a SLAVE has to assume mastership, and a new SLAVE will be generated.
+
+In this mode when node1 fails, unlike in FULL_AUTO mode the partition is _not_ moved from node1 to node3. Instead, Helix will decide to change the state of MyResource_0 on node2 from SLAVE to MASTER, based on the system constraints.
+
+### CUSTOMIZED
+
+Helix offers a third mode called CUSTOMIZED, in which the application controls the placement _and_ state of each replica. The application needs to implement a callback interface that Helix invokes when the cluster state changes.
+Within this callback, the application can recompute the idealstate. Helix will then issue appropriate transitions such that _Idealstate_ and _Currentstate_ converges.
+
+Here\'s an example, again with 3 partitions, 2 replicas per partition, and the MasterSlave state model:
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "REBALANCE_MODE" : "CUSTOMIZED",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ },
+ "mapFields" : {
+ "MyResource_0" : {
+ "N1" : "MASTER",
+ "N2" : "SLAVE",
+ },
+ "MyResource_1" : {
+ "N2" : "MASTER",
+ "N3" : "SLAVE",
+ },
+ "MyResource_2" : {
+ "N3" : "MASTER",
+ "N1" : "SLAVE",
+ }
+ }
+}
+```
+
+Suppose the current state of the system is 'MyResource_0' \-\> {N1:MASTER, N2:SLAVE} and the application changes the ideal state to 'MyResource_0' \-\> {N1:SLAVE,N2:MASTER}. While the application decides which node is MASTER and which is SLAVE, Helix will not blindly issue MASTER\-\-\>SLAVE to N1 and SLAVE\-\-\>MASTER to N2 in parallel, since that might result in a transient state where both N1 and N2 are masters, which violates the MasterSlave constraint that there is exactly one MASTER at a time. Helix will first issue MASTER\-\-\>SLAVE to N1 and after it is completed, it will issue SLAVE\-\-\>MASTER to N2.
+
+### USER_DEFINED
+
+For maximum flexibility, Helix exposes an interface that can allow applications to plug in custom rebalancing logic. By providing the name of a class that implements the Rebalancer interface, Helix will automatically call the contained method whenever there is a change to the live participants in the cluster. For more, see [User-Defined Rebalancer](./tutorial_user_def_rebalancer.html).
+
+### Backwards Compatibility
+
+In previous versions, FULL_AUTO was called AUTO_REBALANCE and SEMI_AUTO was called AUTO. Furthermore, they were presented as the IDEAL_STATE_MODE. Helix supports both IDEAL_STATE_MODE and REBALANCE_MODE, but IDEAL_STATE_MODE is now deprecated and may be phased out in future versions.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/tutorial_spectator.md
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/markdown/tutorial_spectator.md b/website/0.6.8/src/site/markdown/tutorial_spectator.md
new file mode 100644
index 0000000..e43cd6b
--- /dev/null
+++ b/website/0.6.8/src/site/markdown/tutorial_spectator.md
@@ -0,0 +1,75 @@
+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial - Spectator</title>
+</head>
+
+## [Helix Tutorial](./Tutorial.html): Spectator
+
+Next, we\'ll learn how to implement a __spectator__. Typically, a spectator needs to react to changes within the distributed system. Examples: a client that needs to know where to send a request, a topic consumer in a consumer group. The spectator is automatically informed of changes in the _external state_ of the cluster, but it does not have to add any code to keep track of other components in the system.
+
+### Start a Connection
+
+Same as for a participant, The Helix manager is the common component that connects each system component with the cluster.
+
+It requires the following parameters:
+
+* clusterName: A logical name to represent the group of nodes
+* instanceName: A logical name of the process creating the manager instance. Generally this is host:port
+* instanceType: Type of the process. This can be one of the following types, in this case, use SPECTATOR:
+ * CONTROLLER: Process that controls the cluster, any number of controllers can be started but only one will be active at any given time
+ * PARTICIPANT: Process that performs the actual task in the distributed system
+ * SPECTATOR: Process that observes the changes in the cluster
+ * ADMIN: To carry out system admin actions
+* zkConnectString: Connection string to ZooKeeper. This is of the form host1:port1,host2:port2,host3:port3
+
+After the Helix manager instance is created, the only thing that needs to be registered is the listener. When the ExternalView changes, the listener is notified.
+
+A spectator observes the cluster and is notified when the state of the system changes. Helix consolidates the state of entire cluster in one Znode called ExternalView.
+Helix provides a default implementation RoutingTableProvider that caches the cluster state and updates it when there is a change in the cluster.
+
+```
+manager = HelixManagerFactory.getZKHelixManager(clusterName,
+ instanceName,
+ InstanceType.SPECTATOR,
+ zkConnectString);
+manager.connect();
+RoutingTableProvider routingTableProvider = new RoutingTableProvider();
+manager.addExternalViewChangeListener(routingTableProvider);
+```
+
+### Spectator Code
+
+In the following code snippet, the application sends the request to a valid instance by interrogating the external view. Suppose the desired resource for this request is in the partition myDB_1.
+
+```
+// instances = routingTableProvider.getInstances(, "PARTITION_NAME", "PARTITION_STATE");
+instances = routingTableProvider.getInstances("myDB", "myDB_1", "ONLINE");
+
+////////////////////////////////////////////////////////////////////////////////////////////////
+// Application-specific code to send a request to one of the instances //
+////////////////////////////////////////////////////////////////////////////////////////////////
+
+theInstance = instances.get(0); // should choose an instance and throw an exception if none are available
+result = theInstance.sendRequest(yourApplicationRequest, responseObject);
+
+```
+
+When the external view changes, the application needs to react by sending requests to a different instance.
[3/3] helix git commit: Prepare website for 0.6.8 release and add
0.6.8 release notes.
Posted by jx...@apache.org.
Prepare website for 0.6.8 release and add 0.6.8 release notes.
Project: http://git-wip-us.apache.org/repos/asf/helix/repo
Commit: http://git-wip-us.apache.org/repos/asf/helix/commit/09a54c8e
Tree: http://git-wip-us.apache.org/repos/asf/helix/tree/09a54c8e
Diff: http://git-wip-us.apache.org/repos/asf/helix/diff/09a54c8e
Branch: refs/heads/master
Commit: 09a54c8eb70973fe6812c263e94838e80fb288a2
Parents: 01f13c9
Author: Junkai Xue <jx...@linkedin.com>
Authored: Mon Jun 12 16:05:11 2017 -0700
Committer: Junkai Xue <jx...@linkedin.com>
Committed: Mon Jun 12 16:30:31 2017 -0700
----------------------------------------------------------------------
website/0.6.8/pom.xml | 51 ++
website/0.6.8/src/site/apt/privacy-policy.apt | 52 ++
.../src/site/apt/releasenotes/release-0.6.8.apt | 124 ++++
website/0.6.8/src/site/markdown/Building.md | 42 ++
website/0.6.8/src/site/markdown/Features.md | 313 +++++++++
website/0.6.8/src/site/markdown/Quickstart.md | 663 +++++++++++++++++++
website/0.6.8/src/site/markdown/Tutorial.md | 203 ++++++
website/0.6.8/src/site/markdown/index.md | 51 ++
.../src/site/markdown/recipes/lock_manager.md | 236 +++++++
.../markdown/recipes/rabbitmq_consumer_group.md | 213 ++++++
.../recipes/rsync_replicated_file_store.md | 162 +++++
.../site/markdown/recipes/service_discovery.md | 184 +++++
.../site/markdown/recipes/task_dag_execution.md | 199 ++++++
.../0.6.8/src/site/markdown/tutorial_admin.md | 408 ++++++++++++
.../0.6.8/src/site/markdown/tutorial_agent.md | 169 +++++
.../src/site/markdown/tutorial_controller.md | 153 +++++
.../src/site/markdown/tutorial_messaging.md | 70 ++
.../src/site/markdown/tutorial_participant.md | 102 +++
.../src/site/markdown/tutorial_propstore.md | 34 +
.../src/site/markdown/tutorial_rebalance.md | 181 +++++
.../src/site/markdown/tutorial_spectator.md | 75 +++
.../0.6.8/src/site/markdown/tutorial_state.md | 131 ++++
.../site/markdown/tutorial_task_framework.md | 359 ++++++++++
.../src/site/markdown/tutorial_throttling.md | 39 ++
.../markdown/tutorial_user_def_rebalancer.md | 172 +++++
.../0.6.8/src/site/markdown/tutorial_yaml.md | 102 +++
website/0.6.8/src/site/resources/.htaccess | 20 +
website/0.6.8/src/site/resources/download.cgi | 22 +
.../src/site/resources/images/PFS-Generic.png | Bin 0 -> 72435 bytes
.../site/resources/images/RSYNC_BASED_PFS.png | Bin 0 -> 78007 bytes
.../resources/images/TaskFrameworkLayers.png | Bin 0 -> 11622 bytes
website/0.6.8/src/site/site.xml | 140 ++++
website/0.6.8/src/site/xdoc/download.xml.vm | 214 ++++++
website/0.6.8/src/test/conf/testng.xml | 27 +
website/pom.xml | 1 +
35 files changed, 4912 insertions(+)
----------------------------------------------------------------------
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/pom.xml
----------------------------------------------------------------------
diff --git a/website/0.6.8/pom.xml b/website/0.6.8/pom.xml
new file mode 100644
index 0000000..59fcf2c
--- /dev/null
+++ b/website/0.6.8/pom.xml
@@ -0,0 +1,51 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+ <modelVersion>4.0.0</modelVersion>
+
+ <parent>
+ <groupId>org.apache.helix</groupId>
+ <artifactId>website</artifactId>
+ <version>0.7.2-SNAPSHOT</version>
+ </parent>
+
+ <artifactId>0.6.8-docs</artifactId>
+ <packaging>bundle</packaging>
+ <name>Apache Helix :: Website :: 0.6.8</name>
+
+ <properties>
+ </properties>
+
+ <dependencies>
+ <dependency>
+ <groupId>org.testng</groupId>
+ <artifactId>testng</artifactId>
+ <version>6.0.1</version>
+ </dependency>
+ </dependencies>
+ <build>
+ <pluginManagement>
+ <plugins>
+ </plugins>
+ </pluginManagement>
+ <plugins>
+ </plugins>
+ </build>
+</project>
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/apt/privacy-policy.apt
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/apt/privacy-policy.apt b/website/0.6.8/src/site/apt/privacy-policy.apt
new file mode 100644
index 0000000..ada9363
--- /dev/null
+++ b/website/0.6.8/src/site/apt/privacy-policy.apt
@@ -0,0 +1,52 @@
+ ----
+ Privacy Policy
+ -----
+ Olivier Lamy
+ -----
+ 2013-02-04
+ -----
+
+~~ Licensed to the Apache Software Foundation (ASF) under one
+~~ or more contributor license agreements. See the NOTICE file
+~~ distributed with this work for additional information
+~~ regarding copyright ownership. The ASF licenses this file
+~~ to you under the Apache License, Version 2.0 (the
+~~ "License"); you may not use this file except in compliance
+~~ with the License. You may obtain a copy of the License at
+~~
+~~ http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing,
+~~ software distributed under the License is distributed on an
+~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+~~ KIND, either express or implied. See the License for the
+~~ specific language governing permissions and limitations
+~~ under the License.
+
+Privacy Policy
+
+ Information about your use of this website is collected using server access logs and a tracking cookie. The
+ collected information consists of the following:
+
+ [[1]] The IP address from which you access the website;
+
+ [[2]] The type of browser and operating system you use to access our site;
+
+ [[3]] The date and time you access our site;
+
+ [[4]] The pages you visit; and
+
+ [[5]] The addresses of pages from where you followed a link to our site.
+
+ []
+
+ Part of this information is gathered using a tracking cookie set by the
+ {{{http://www.google.com/analytics/}Google Analytics}} service and handled by Google as described in their
+ {{{http://www.google.com/privacy.html}privacy policy}}. See your browser documentation for instructions on how to
+ disable the cookie if you prefer not to share this data with Google.
+
+ We use the gathered information to help us make our site more useful to visitors and to better understand how and
+ when our site is used. We do not track or collect personally identifiable information or associate gathered data
+ with any personally identifying information from other sources.
+
+ By using this website, you consent to the collection of this data in the manner and for the purpose described above.
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/apt/releasenotes/release-0.6.8.apt
----------------------------------------------------------------------
diff --git a/website/0.6.8/src/site/apt/releasenotes/release-0.6.8.apt b/website/0.6.8/src/site/apt/releasenotes/release-0.6.8.apt
new file mode 100644
index 0000000..28571c0
--- /dev/null
+++ b/website/0.6.8/src/site/apt/releasenotes/release-0.6.8.apt
@@ -0,0 +1,124 @@
+ -----
+ Release Notes for Apache Helix 0.6.8
+ -----
+
+~~ Licensed to the Apache Software Foundation (ASF) under one
+~~ or more contributor license agreements. See the NOTICE file
+~~ distributed with this work for additional information
+~~ regarding copyright ownership. The ASF licenses this file
+~~ to you under the Apache License, Version 2.0 (the
+~~ "License"); you may not use this file except in compliance
+~~ with the License. You may obtain a copy of the License at
+~~
+~~ http://www.apache.org/licenses/LICENSE-2.0
+~~
+~~ Unless required by applicable law or agreed to in writing,
+~~ software distributed under the License is distributed on an
+~~ "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+~~ KIND, either express or implied. See the License for the
+~~ specific language governing permissions and limitations
+~~ under the License.
+
+~~ NOTE: For help with the syntax of this file, see:
+~~ http://maven.apache.org/guides/mini/guide-apt-format.html
+
+Release Notes for Apache Helix 0.6.8
+
+ The Apache Helix team would like to announce the release of Apache Helix 0.6.8.
+
+ This is the eleventh release under the Apache umbrella, and the seventh as a top-level project.
+
+ Helix is a generic cluster management framework used for the automatic management of partitioned, replicated and distributed resources hosted on a cluster of nodes. Helix provides the following features:
+
+ * Automatic assignment of resource/partition to nodes
+
+ * Node failure detection and recovery
+
+ * Dynamic addition of Resources
+
+ * Dynamic addition of nodes to the cluster
+
+ * Pluggable distributed state machine to manage the state of a resource via state transitions
+
+ * Automatic load balancing and throttling of transitions
+
+[]
+
+* Detailed Changes
+
+** Feature
+
+ * [Helix-656] Support customize batch state transition thread pool.
+
+ * Support cancel tasks with synchronized check task status.
+
+ * Add support of setting/updating Cluster/Resource/Instance configs in ConfigAccessor.
+
+ * Add cluster-level and resource-level config option to allow disable delayed rebalance of entire cluster or individual resource.
+
+ * New DelayedAutoRebalancer featured with delayed partition movements during rebalancing.
+
+ * Add support for flexible hirerachy representation of a cluster topology.
+
+ * Add StrictMatchExternalViewVerifier that verifies whether the ExternalViews of given resources (or all resources in the cluster) match exactly as its ideal mapping (in idealstate).
+
+ * Add Multi-round CRUSH rebalance strategy.
+
+ * Add option to allow persisting best possible partition assignment in IdealState for semi-auto and full-auto modes.
+
+ * Support of client's customized threadpool for state-transition message handling.
+
+ * Support delaying jobs schedule with configurable delay time and start time
+
+
+** Bug
+
+ * [HELIX-657] Fix unexpected idealstate overwrite when persist assignment is on.
+
+ * [HELIX-631] Fix AutoRebalanceStrategy replica not assigned.
+
+ * [HELIX-653] Fix enable/disable partition in instances for resource specific.
+
+ * Make map in NotificationContext synchronized.
+
+ * Fix bug in AutoRebalanceStrategy to try to assign orphan replicas to its preferred nodes instead of random nodes.
+
+ * Fix a bug in BestPossibleExternalViewVerifier.
+
+ * Fix BestPossibleExternalViewVerifier toString NPE.
+
+ * Do not set MaxPartitionPerNode in IdealState if it is not greater than 0.
+
+
+** Improvement
+
+ * [HELIX-660] Configurable operation timeout for Helix ZKClient.
+
+ * Allow user to enable persisting preference list and best possible state map into IdealState in full-auto mode.
+
+ * Expose Callbacks that can let async operation of ZkClient function.
+
+ * Creating a separate threadpool to handle batchMessages.
+
+ * Auto compress ZNode that are greater than 1MB.
+
+ * Ignore instances with no instance configuration.
+
+ * Avoid moving partitions unnecessarily when auto-rebalancing using default AutoRebalanceStrategy.
+
+ * Move all options from IdealState to ResourceConfig, add Bulder for building ResourceConfig, and a new RebalanceConfig to hold all rebalance options for a resource.
+
+ * Persist controller leader change history with timestamp for each leader controller.
+
+ * Persist participant's offline timestamp in ParticipantHistory.
+
+ * Persist session change history with timestamp for each participant.
+
+ * Make synchronized for AsyncCallback.startTimer to avoid race condition.
+
+
+[]
+
+Cheers,
+--
+The Apache Helix Team
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/Building.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+Build Instructions
+------------------
+
+### From Source
+
+Requirements: JDK 1.6+, Maven 2.0.8+
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+mvn install package -DskipTests
+```
+
+### Maven Dependency
+
+```
+<dependency>
+ <groupId>org.apache.helix</groupId>
+ <artifactId>helix-core</artifactId>
+ <version>0.6.8</version>
+</dependency>
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/Features.md
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diff --git a/website/0.6.8/src/site/markdown/Features.md b/website/0.6.8/src/site/markdown/Features.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Features</title>
+</head>
+
+Features
+----------------------------
+
+
+### CONFIGURING IDEALSTATE
+
+
+Read concepts page for definition of Idealstate.
+
+The placement of partitions in a DDS is very critical for reliability and scalability of the system.
+For example, when a node fails, it is important that the partitions hosted on that node are reallocated evenly among the remaining nodes. Consistent hashing is one such algorithm that can guarantee this.
+Helix by default comes with a variant of consistent hashing based of the RUSH algorithm.
+
+This means given a number of partitions, replicas and number of nodes Helix does the automatic assignment of partition to nodes such that
+
+* Each node has the same number of partitions and replicas of the same partition do not stay on the same node.
+* When a node fails, the partitions will be equally distributed among the remaining nodes
+* When new nodes are added, the number of partitions moved will be minimized along with satisfying the above two criteria.
+
+
+Helix provides multiple ways to control the placement and state of a replica.
+
+```
+
+ |AUTO REBALANCE| AUTO | CUSTOM |
+ -----------------------------------------
+ LOCATION | HELIX | APP | APP |
+ -----------------------------------------
+ STATE | HELIX | HELIX | APP |
+ -----------------------------------------
+```
+
+#### HELIX EXECUTION MODE
+
+
+Idealstate is defined as the state of the DDS when all nodes are up and running and healthy.
+Helix uses this as the target state of the system and computes the appropriate transitions needed in the system to bring it to a stable state.
+
+Helix supports 3 different execution modes which allows application to explicitly control the placement and state of the replica.
+
+##### AUTO_REBALANCE
+
+When the idealstate mode is set to AUTO_REBALANCE, Helix controls both the location of the replica along with the state. This option is useful for applications where creation of a replica is not expensive. Example
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO_REBALANCE",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ }
+ "listFields" : {
+ "MyResource_0" : [],
+ "MyResource_1" : [],
+ "MyResource_2" : []
+ },
+ "mapFields" : {
+ }
+}
+```
+
+If there are 3 nodes in the cluster, then Helix will internally compute the ideal state as
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ },
+ "mapFields" : {
+ "MyResource_0" : {
+ "N1" : "MASTER",
+ "N2" : "SLAVE",
+ },
+ "MyResource_1" : {
+ "N2" : "MASTER",
+ "N3" : "SLAVE",
+ },
+ "MyResource_2" : {
+ "N3" : "MASTER",
+ "N1" : "SLAVE",
+ }
+ }
+}
+```
+
+Another typical example is evenly distributing a group of tasks among the currently alive processes. For example, if there are 60 tasks and 4 nodes, Helix assigns 15 tasks to each node.
+When one node fails Helix redistributes its 15 tasks to the remaining 3 nodes. Similarly, if a node is added, Helix re-allocates 3 tasks from each of the 4 nodes to the 5th node.
+
+#### AUTO
+
+When the idealstate mode is set to AUTO, Helix only controls STATE of the replicas where as the location of the partition is controlled by application. Example: The below idealstate indicates thats 'MyResource_0' must be only on node1 and node2. But gives the control of assigning the STATE to Helix.
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ }
+ "listFields" : {
+ "MyResource_0" : [node1, node2],
+ "MyResource_1" : [node2, node3],
+ "MyResource_2" : [node3, node1]
+ },
+ "mapFields" : {
+ }
+}
+```
+In this mode when node1 fails, unlike in AUTO-REBALANCE mode the partition is not moved from node1 to others nodes in the cluster. Instead, Helix will decide to change the state of MyResource_0 in N2 based on the system constraints. For example, if a system constraint specified that there should be 1 Master and if the Master failed, then node2 will be made the new master.
+
+#### CUSTOM
+
+Helix offers a third mode called CUSTOM, in which application can completely control the placement and state of each replica. Applications will have to implement an interface that Helix will invoke when the cluster state changes.
+Within this callback, the application can recompute the idealstate. Helix will then issue appropriate transitions such that Idealstate and Currentstate converges.
+
+```
+{
+ "id" : "MyResource",
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "CUSTOM",
+ "NUM_PARTITIONS" : "3",
+ "REPLICAS" : "2",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ },
+ "mapFields" : {
+ "MyResource_0" : {
+ "N1" : "MASTER",
+ "N2" : "SLAVE",
+ },
+ "MyResource_1" : {
+ "N2" : "MASTER",
+ "N3" : "SLAVE",
+ },
+ "MyResource_2" : {
+ "N3" : "MASTER",
+ "N1" : "SLAVE",
+ }
+ }
+}
+```
+
+For example, the current state of the system might be 'MyResource_0' -> {N1:MASTER,N2:SLAVE} and the application changes the ideal state to 'MyResource_0' -> {N1:SLAVE,N2:MASTER}. Helix will not blindly issue MASTER-->SLAVE to N1 and SLAVE-->MASTER to N2 in parallel since it might result in a transient state where both N1 and N2 are masters.
+Helix will first issue MASTER-->SLAVE to N1 and after its completed it will issue SLAVE-->MASTER to N2.
+
+
+### State Machine Configuration
+
+Helix comes with 3 default state models that are most commonly used. Its possible to have multiple state models in a cluster.
+Every resource that is added should have a reference to the state model.
+
+* MASTER-SLAVE: Has 3 states OFFLINE,SLAVE,MASTER. Max masters is 1. Slaves will be based on the replication factor. Replication factor can be specified while adding the resource
+* ONLINE-OFFLINE: Has 2 states OFFLINE and ONLINE. Very simple state model and most applications start off with this state model.
+* LEADER-STANDBY:1 Leader and many stand bys. In general the standby's are idle.
+
+Apart from providing the state machine configuration, one can specify the constraints of states and transitions.
+
+For example one can say
+Master:1. Max number of replicas in Master state at any time is 1.
+OFFLINE-SLAVE:5 Max number of Offline-Slave transitions that can happen concurrently in the system
+
+STATE PRIORITY
+Helix uses greedy approach to satisfy the state constraints. For example if the state machine configuration says it needs 1 master and 2 slaves but only 1 node is active, Helix must promote it to master. This behavior is achieved by providing the state priority list as MASTER,SLAVE.
+
+STATE TRANSITION PRIORITY
+Helix tries to fire as many transitions as possible in parallel to reach the stable state without violating constraints. By default Helix simply sorts the transitions alphabetically and fires as many as it can without violating the constraints.
+One can control this by overriding the priority order.
+
+### Config management
+
+Helix allows applications to store application specific properties. The configuration can have different scopes.
+
+* Cluster
+* Node specific
+* Resource specific
+* Partition specific
+
+Helix also provides notifications when any configs are changed. This allows applications to support dynamic configuration changes.
+
+See HelixManager.getConfigAccessor for more info
+
+### Intra cluster messaging api
+
+This is an interesting feature which is quite useful in practice. Often times, nodes in DDS requires a mechanism to interact with each other. One such requirement is a process of bootstrapping a replica.
+
+Consider a search system use case where the index replica starts up and it does not have an index. One of the commonly used solutions is to get the index from a common location or to copy the index from another replica.
+Helix provides a messaging api, that can be used to talk to other nodes in the system. The value added that Helix provides here is, message recipient can be specified in terms of resource,
+partition, state and Helix ensures that the message is delivered to all of the required recipients. In this particular use case, the instance can specify the recipient criteria as all replicas of P1.
+Since Helix is aware of the global state of the system, it can send the message to appropriate nodes. Once the nodes respond Helix provides the bootstrapping replica with all the responses.
+
+This is a very generic api and can also be used to schedule various periodic tasks in the cluster like data backups etc.
+System Admins can also perform adhoc tasks like on demand backup or execute a system command(like rm -rf ;-)) across all nodes.
+
+```
+ ClusterMessagingService messagingService = manager.getMessagingService();
+ //CONSTRUCT THE MESSAGE
+ Message requestBackupUriRequest = new Message(
+ MessageType.USER_DEFINE_MSG, UUID.randomUUID().toString());
+ requestBackupUriRequest
+ .setMsgSubType(BootstrapProcess.REQUEST_BOOTSTRAP_URL);
+ requestBackupUriRequest.setMsgState(MessageState.NEW);
+ //SET THE RECIPIENT CRITERIA, All nodes that satisfy the criteria will receive the message
+ Criteria recipientCriteria = new Criteria();
+ recipientCriteria.setInstanceName("%");
+ recipientCriteria.setRecipientInstanceType(InstanceType.PARTICIPANT);
+ recipientCriteria.setResource("MyDB");
+ recipientCriteria.setPartition("");
+ //Should be processed only the process that is active at the time of sending the message.
+ //This means if the recipient is restarted after message is sent, it will not be processed.
+ recipientCriteria.setSessionSpecific(true);
+ // wait for 30 seconds
+ int timeout = 30000;
+ //The handler that will be invoked when any recipient responds to the message.
+ BootstrapReplyHandler responseHandler = new BootstrapReplyHandler();
+ //This will return only after all recipients respond or after timeout.
+ int sentMessageCount = messagingService.sendAndWait(recipientCriteria,
+ requestBackupUriRequest, responseHandler, timeout);
+```
+
+See HelixManager.getMessagingService for more info.
+
+
+### Application specific property storage
+
+There are several usecases where applications needs support for distributed data structures. Helix uses Zookeeper to store the application data and hence provides notifications when the data changes.
+One value add Helix provides is the ability to specify cache the data and also write through cache. This is more efficient than reading from ZK every time.
+
+See HelixManager.getHelixPropertyStore
+
+### Throttling
+
+Since all state changes in the system are triggered through transitions, Helix can control the number of transitions that can happen in parallel. Some of the transitions may be light weight but some might involve moving data around which is quite expensive.
+Helix allows applications to set threshold on transitions. The threshold can be set at the multiple scopes.
+
+* MessageType e.g STATE_TRANSITION
+* TransitionType e.g SLAVE-MASTER
+* Resource e.g database
+* Node i.e per node max transitions in parallel.
+
+See HelixManager.getHelixAdmin.addMessageConstraint()
+
+### Health monitoring and alerting
+
+This in currently in development mode, not yet productionized.
+
+Helix provides ability for each node in the system to report health metrics on a periodic basis.
+Helix supports multiple ways to aggregate these metrics like simple SUM, AVG, EXPONENTIAL DECAY, WINDOW. Helix will only persist the aggregated value.
+Applications can define threshold on the aggregate values according to the SLA's and when the SLA is violated Helix will fire an alert.
+Currently Helix only fires an alert but eventually we plan to use this metrics to either mark the node dead or load balance the partitions.
+This feature will be valuable in for distributed systems that support multi-tenancy and have huge variation in work load patterns. Another place this can be used is to detect skewed partitions and rebalance the cluster.
+
+This feature is not yet stable and do not recommend to be used in production.
+
+
+### Controller deployment modes
+
+Read Architecture wiki for more details on the Role of a controller. In simple words, it basically controls the participants in the cluster by issuing transitions.
+
+Helix provides multiple options to deploy the controller.
+
+#### STANDALONE
+
+Controller can be started as a separate process to manage a cluster. This is the recommended approach. How ever since one controller can be a single point of failure, multiple controller processes are required for reliability.
+Even if multiple controllers are running only one will be actively managing the cluster at any time and is decided by a leader election process. If the leader fails, another leader will resume managing the cluster.
+
+Even though we recommend this method of deployment, it has the drawback of having to manage an additional service for each cluster. See Controller As a Service option.
+
+#### EMBEDDED
+
+If setting up a separate controller process is not viable, then it is possible to embed the controller as a library in each of the participant.
+
+#### CONTROLLER AS A SERVICE
+
+One of the cool feature we added in helix was use a set of controllers to manage a large number of clusters.
+For example if you have X clusters to be managed, instead of deploying X*3(3 controllers for fault tolerance) controllers for each cluster, one can deploy only 3 controllers. Each controller can manage X/3 clusters.
+If any controller fails the remaining two will manage X/2 clusters. At LinkedIn, we always deploy controllers in this mode.
+
+
+
+
+
+
+
+
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/Quickstart.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Quickstart</title>
+</head>
+
+Quickstart
+---------
+
+Get Helix
+---------
+
+First, let\'s get Helix. Either build it, or download it.
+
+### Build
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+mvn install package -DskipTests
+cd helix-core/target/helix-core-pkg/bin # This folder contains all the scripts used in following sections
+chmod +x *
+```
+
+### Download
+
+Download the 0.6.8 release package [here](./download.html)
+
+Overview
+--------
+
+In this Quickstart, we\'ll set up a master-slave replicated, partitioned system. Then we\'ll demonstrate how to add a node, rebalance the partitions, and show how Helix manages failover.
+
+
+Let\'s Do It
+------------
+
+Helix provides command line interfaces to set up the cluster and view the cluster state. The best way to understand how Helix views a cluster is to build a cluster.
+
+### Get to the Tools Directory
+
+If you built the code:
+
+```
+cd helix/helix/helix-core/target/helix-core-pkg/bin
+```
+
+If you downloaded the release package, extract it.
+
+
+Short Version
+-------------
+You can observe the components working together in this demo, which does the following:
+
+* Create a cluster
+* Add 2 nodes (participants) to the cluster
+* Set up a resource with 6 partitions and 2 replicas: 1 Master, and 1 Slave per partition
+* Show the cluster state after Helix balances the partitions
+* Add a third node
+* Show the cluster state. Note that the third node has taken mastership of 2 partitions.
+* Kill the third node (Helix takes care of failover)
+* Show the cluster state. Note that the two surviving nodes take over mastership of the partitions from the failed node
+
+### Run the Demo
+
+```
+cd helix/helix/helix-core/target/helix-core-pkg/bin
+./quickstart.sh
+```
+
+#### The Initial Setup
+
+2 nodes are set up and the partitions are rebalanced.
+
+The cluster state is as follows:
+
+```
+CLUSTER STATE: After starting 2 nodes
+ localhost_12000 localhost_12001
+MyResource_0 M S
+MyResource_1 S M
+MyResource_2 M S
+MyResource_3 M S
+MyResource_4 S M
+MyResource_5 S M
+```
+
+Note there is one master and one slave per partition.
+
+#### Add a Node
+
+A third node is added and the cluster is rebalanced.
+
+The cluster state changes to:
+
+```
+CLUSTER STATE: After adding a third node
+ localhost_12000 localhost_12001 localhost_12002
+MyResource_0 S M S
+MyResource_1 S S M
+MyResource_2 M S S
+MyResource_3 S S M
+MyResource_4 M S S
+MyResource_5 S M S
+```
+
+Note there is one master and _two_ slaves per partition. This is expected because there are three nodes.
+
+#### Kill a Node
+
+Finally, a node is killed to simulate a failure
+
+Helix makes sure each partition has a master. The cluster state changes to:
+
+```
+CLUSTER STATE: After the 3rd node stops/crashes
+ localhost_12000 localhost_12001 localhost_12002
+MyResource_0 S M -
+MyResource_1 S M -
+MyResource_2 M S -
+MyResource_3 M S -
+MyResource_4 M S -
+MyResource_5 S M -
+```
+
+
+Long Version
+------------
+Now you can run the same steps by hand. In this detailed version, we\'ll do the following:
+
+* Define a cluster
+* Add two nodes to the cluster
+* Add a 6-partition resource with 1 master and 2 slave replicas per partition
+* Verify that the cluster is healthy and inspect the Helix view
+* Expand the cluster: add a few nodes and rebalance the partitions
+* Failover: stop a node and verify the mastership transfer
+
+### Install and Start ZooKeeper
+
+Zookeeper can be started in standalone mode or replicated mode.
+
+More information is available at
+
+* http://zookeeper.apache.org/doc/r3.3.3/zookeeperStarted.html
+* http://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_zkMulitServerSetup
+
+In this example, let\'s start zookeeper in local mode.
+
+#### Start ZooKeeper Locally on Port 2199
+
+```
+./start-standalone-zookeeper.sh 2199 &
+```
+
+### Define the Cluster
+
+The helix-admin tool is used for cluster administration tasks. In the Quickstart, we\'ll use the command line interface. Helix supports a REST interface as well.
+
+zookeeper_address is of the format host:port e.g localhost:2199 for standalone or host1:port,host2:port for multi-node.
+
+Next, we\'ll set up a cluster MYCLUSTER cluster with these attributes:
+
+* 3 instances running on localhost at ports 12913,12914,12915
+* One database named myDB with 6 partitions
+* Each partition will have 3 replicas with 1 master, 2 slaves
+* ZooKeeper running locally at localhost:2199
+
+#### Create the Cluster MYCLUSTER
+
+```
+# ./helix-admin.sh --zkSvr <zk_address> --addCluster <clustername>
+./helix-admin.sh --zkSvr localhost:2199 --addCluster MYCLUSTER
+```
+
+### Add Nodes to the Cluster
+
+In this case we\'ll add three nodes: localhost:12913, localhost:12914, localhost:12915
+
+```
+# helix-admin.sh --zkSvr <zk_address> --addNode <clustername> <host:port>
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12913
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12914
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12915
+```
+
+### Define the Resource and Partitioning
+
+In this example, the resource is a database, partitioned 6 ways. Note that in a production system, it\'s common to over-partition for better load balancing. Helix has been used in production to manage hundreds of databases each with 10s or 100s of partitions running on 10s of physical nodes.
+
+#### Create a Database with 6 Partitions using the MasterSlave State Model
+
+Helix ensures there will be exactly one master for each partition.
+
+```
+# helix-admin.sh --zkSvr <zk_address> --addResource <clustername> <resourceName> <numPartitions> <StateModelName>
+./helix-admin.sh --zkSvr localhost:2199 --addResource MYCLUSTER myDB 6 MasterSlave
+```
+
+#### Let Helix Assign Partitions to Nodes
+
+This command will distribute the partitions amongst all the nodes in the cluster. In this example, each partition has 3 replicas.
+
+```
+# helix-admin.sh --zkSvr <zk_address> --rebalance <clustername> <resourceName> <replication factor>
+./helix-admin.sh --zkSvr localhost:2199 --rebalance MYCLUSTER myDB 3
+```
+
+Now the cluster is defined in ZooKeeper. The nodes (localhost:12913, localhost:12914, localhost:12915) and resource (myDB, with 6 partitions using the MasterSlave model) are all properly configured. And the _IdealState_ has been calculated, assuming a replication factor of 3.
+
+### Start the Helix Controller
+
+Now that the cluster is defined in ZooKeeper, the Helix controller can manage the cluster.
+
+```
+# Start the cluster manager, which will manage MYCLUSTER
+./run-helix-controller.sh --zkSvr localhost:2199 --cluster MYCLUSTER 2>&1 > /tmp/controller.log &
+```
+
+### Start up the Cluster to be Managed
+
+We\'ve started up ZooKeeper, defined the cluster, the resources, the partitioning, and started up the Helix controller. Next, we\'ll start up the nodes of the system to be managed. Each node is a Participant, which is an instance of the system component to be managed. Helix assigns work to Participants, keeps track of their roles and health, and takes action when a node fails.
+
+```
+# start up each instance. These are mock implementations that are actively managed by Helix
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12913 --stateModelType MasterSlave 2>&1 > /tmp/participant_12913.log
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12914 --stateModelType MasterSlave 2>&1 > /tmp/participant_12914.log
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12915 --stateModelType MasterSlave 2>&1 > /tmp/participant_12915.log
+```
+
+### Inspect the Cluster
+
+Now, let\'s see the Helix view of our cluster. We\'ll work our way down as follows:
+
+```
+Clusters -> MYCLUSTER -> instances -> instance detail
+ -> resources -> resource detail
+ -> partitions
+```
+
+A single Helix controller can manage multiple clusters, though so far, we\'ve only defined one cluster. Let\'s see:
+
+```
+# List existing clusters
+./helix-admin.sh --zkSvr localhost:2199 --listClusters
+
+Existing clusters:
+MYCLUSTER
+```
+
+Now, let\'s see the Helix view of MYCLUSTER:
+
+```
+# helix-admin.sh --zkSvr <zk_address> --listClusterInfo <clusterName>
+./helix-admin.sh --zkSvr localhost:2199 --listClusterInfo MYCLUSTER
+
+Existing resources in cluster MYCLUSTER:
+myDB
+Instances in cluster MYCLUSTER:
+localhost_12915
+localhost_12914
+localhost_12913
+```
+
+Let\'s look at the details of an instance:
+
+```
+# ./helix-admin.sh --zkSvr <zk_address> --listInstanceInfo <clusterName> <InstanceName>
+./helix-admin.sh --zkSvr localhost:2199 --listInstanceInfo MYCLUSTER localhost_12913
+
+InstanceConfig: {
+ "id" : "localhost_12913",
+ "mapFields" : {
+ },
+ "listFields" : {
+ },
+ "simpleFields" : {
+ "HELIX_ENABLED" : "true",
+ "HELIX_HOST" : "localhost",
+ "HELIX_PORT" : "12913"
+ }
+}
+```
+
+
+#### Query Information about a Resource
+
+```
+# helix-admin.sh --zkSvr <zk_address> --listResourceInfo <clusterName> <resourceName>
+./helix-admin.sh --zkSvr localhost:2199 --listResourceInfo MYCLUSTER myDB
+
+IdealState for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_1" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "MASTER"
+ },
+ "myDB_4" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ "myDB_0" : [ "localhost_12914", "localhost_12913", "localhost_12915" ],
+ "myDB_1" : [ "localhost_12915", "localhost_12913", "localhost_12914" ],
+ "myDB_2" : [ "localhost_12913", "localhost_12915", "localhost_12914" ],
+ "myDB_3" : [ "localhost_12915", "localhost_12913", "localhost_12914" ],
+ "myDB_4" : [ "localhost_12913", "localhost_12914", "localhost_12915" ],
+ "myDB_5" : [ "localhost_12914", "localhost_12915", "localhost_12913" ]
+ },
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO",
+ "REBALANCE_MODE" : "SEMI_AUTO",
+ "NUM_PARTITIONS" : "6",
+ "REPLICAS" : "3",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ "STATE_MODEL_FACTORY_NAME" : "DEFAULT"
+ }
+}
+
+ExternalView for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_1" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "MASTER"
+ },
+ "myDB_4" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12914" : "SLAVE",
+ "localhost_12915" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ },
+ "simpleFields" : {
+ "BUCKET_SIZE" : "0"
+ }
+}
+```
+
+Now, let\'s look at one of the partitions:
+
+```
+# helix-admin.sh --zkSvr <zk_address> --listResourceInfo <clusterName> <partition>
+./helix-admin.sh --zkSvr localhost:2199 --listResourceInfo mycluster myDB_0
+```
+
+### Expand the Cluster
+
+Next, we\'ll show how Helix does the work that you\'d otherwise have to build into your system. When you add capacity to your cluster, you want the work to be evenly distributed. In this example, we started with 3 nodes, with 6 partitions. The partitions were evenly balanced, 2 masters and 4 slaves per node. Let\'s add 3 more nodes: localhost:12916, localhost:12917, localhost:12918
+
+```
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12916
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12917
+./helix-admin.sh --zkSvr localhost:2199 --addNode MYCLUSTER localhost:12918
+```
+
+And start up these instances:
+
+```
+# start up each instance. These are mock implementations that are actively managed by Helix
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12916 --stateModelType MasterSlave 2>&1 > /tmp/participant_12916.log
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12917 --stateModelType MasterSlave 2>&1 > /tmp/participant_12917.log
+./start-helix-participant.sh --zkSvr localhost:2199 --cluster MYCLUSTER --host localhost --port 12918 --stateModelType MasterSlave 2>&1 > /tmp/participant_12918.log
+```
+
+
+And now, let Helix do the work for you. To shift the work, simply rebalance. After the rebalance, each node will have one master and two slaves.
+
+```
+./helix-admin.sh --zkSvr localhost:2199 --rebalance MYCLUSTER myDB 3
+```
+
+### View the Cluster
+
+OK, let\'s see how it looks:
+
+
+```
+./helix-admin.sh --zkSvr localhost:2199 --listResourceInfo MYCLUSTER myDB
+
+IdealState for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12917" : "MASTER"
+ },
+ "myDB_1" : {
+ "localhost_12916" : "SLAVE",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12915" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_4" : {
+ "localhost_12916" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ "myDB_0" : [ "localhost_12917", "localhost_12913", "localhost_12914" ],
+ "myDB_1" : [ "localhost_12918", "localhost_12917", "localhost_12916" ],
+ "myDB_2" : [ "localhost_12913", "localhost_12917", "localhost_12918" ],
+ "myDB_3" : [ "localhost_12915", "localhost_12917", "localhost_12918" ],
+ "myDB_4" : [ "localhost_12916", "localhost_12917", "localhost_12918" ],
+ "myDB_5" : [ "localhost_12914", "localhost_12915", "localhost_12913" ]
+ },
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO",
+ "REBALANCE_MODE" : "SEMI_AUTO",
+ "NUM_PARTITIONS" : "6",
+ "REPLICAS" : "3",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ "STATE_MODEL_FACTORY_NAME" : "DEFAULT"
+ }
+}
+
+ExternalView for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12917" : "MASTER"
+ },
+ "myDB_1" : {
+ "localhost_12916" : "SLAVE",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12915" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_4" : {
+ "localhost_12916" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ },
+ "simpleFields" : {
+ "BUCKET_SIZE" : "0"
+ }
+}
+```
+
+Mission accomplished. The partitions are nicely balanced.
+
+### How about Failover?
+
+Building a fault tolerant system isn\'t trivial, but with Helix, it\'s easy. Helix detects a failed instance, and triggers mastership transfer automatically.
+
+First, let's fail an instance. In this example, we\'ll kill localhost:12918 to simulate a failure.
+
+We lost localhost:12918, so myDB_1 lost its MASTER. Helix can fix that, it will transfer mastership to a healthy node that is currently a SLAVE, say localhost:12197. Helix balances the load as best as it can, given there are 6 partitions on 5 nodes. Let\'s see:
+
+
+```
+./helix-admin.sh --zkSvr localhost:2199 --listResourceInfo MYCLUSTER myDB
+
+IdealState for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12917" : "MASTER"
+ },
+ "myDB_1" : {
+ "localhost_12916" : "SLAVE",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12915" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_4" : {
+ "localhost_12916" : "MASTER",
+ "localhost_12917" : "SLAVE",
+ "localhost_12918" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ "myDB_0" : [ "localhost_12917", "localhost_12913", "localhost_12914" ],
+ "myDB_1" : [ "localhost_12918", "localhost_12917", "localhost_12916" ],
+ "myDB_2" : [ "localhost_12913", "localhost_12918", "localhost_12917" ],
+ "myDB_3" : [ "localhost_12915", "localhost_12918", "localhost_12917" ],
+ "myDB_4" : [ "localhost_12916", "localhost_12917", "localhost_12918" ],
+ "myDB_5" : [ "localhost_12914", "localhost_12915", "localhost_12913" ]
+ },
+ "simpleFields" : {
+ "IDEAL_STATE_MODE" : "AUTO",
+ "REBALANCE_MODE" : "SEMI_AUTO",
+ "NUM_PARTITIONS" : "6",
+ "REPLICAS" : "3",
+ "STATE_MODEL_DEF_REF" : "MasterSlave",
+ "STATE_MODEL_FACTORY_NAME" : "DEFAULT"
+ }
+}
+
+ExternalView for myDB:
+{
+ "id" : "myDB",
+ "mapFields" : {
+ "myDB_0" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "SLAVE",
+ "localhost_12917" : "MASTER"
+ },
+ "myDB_1" : {
+ "localhost_12916" : "SLAVE",
+ "localhost_12917" : "MASTER"
+ },
+ "myDB_2" : {
+ "localhost_12913" : "MASTER",
+ "localhost_12917" : "SLAVE"
+ },
+ "myDB_3" : {
+ "localhost_12915" : "MASTER",
+ "localhost_12917" : "SLAVE"
+ },
+ "myDB_4" : {
+ "localhost_12916" : "MASTER",
+ "localhost_12917" : "SLAVE"
+ },
+ "myDB_5" : {
+ "localhost_12913" : "SLAVE",
+ "localhost_12914" : "MASTER",
+ "localhost_12915" : "SLAVE"
+ }
+ },
+ "listFields" : {
+ },
+ "simpleFields" : {
+ "BUCKET_SIZE" : "0"
+ }
+}
+```
+
+As we\'ve seen in this Quickstart, Helix takes care of partitioning, load balancing, elasticity, failure detection and recovery.
+
+### ZooInspector
+
+You can view all of the underlying data by going direct to zookeeper. Use ZooInspector that comes with zookeeper to browse the data. This is a java applet (make sure you have X windows)
+
+To start zooinspector run the following command from <zk_install_directory>/contrib/ZooInspector
+
+```
+java -cp zookeeper-3.3.3-ZooInspector.jar:lib/jtoaster-1.0.4.jar:../../lib/log4j-1.2.15.jar:../../zookeeper-3.3.3.jar org.apache.zookeeper.inspector.ZooInspector
+```
+
+### Next
+
+Now that you understand the idea of Helix, read the [tutorial](./Tutorial.html) to learn how to choose the right state model and constraints for your system, and how to implement it. In many cases, the built-in features meet your requirements. And best of all, Helix is a customizable framework, so you can plug in your own behavior, while retaining the automation provided by Helix.
+
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/Tutorial.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Tutorial</title>
+</head>
+
+# Helix Tutorial
+
+In this tutorial, we will cover the roles of a Helix-managed cluster, and show the code you need to write to integrate with it. In many cases, there is a simple default behavior that is often appropriate, but you can also customize the behavior.
+
+Convention: we first cover the _basic_ approach, which is the easiest to implement. Then, we'll describe _advanced_ options, which give you more control over the system behavior, but require you to write more code.
+
+
+### Prerequisites
+
+1. Read [Concepts/Terminology](../Concepts.html) and [Architecture](../Architecture.html)
+2. Read the [Quickstart guide](./Quickstart.html) to learn how Helix models and manages a cluster
+3. Install Helix source. See: [Quickstart](./Quickstart.html) for the steps.
+
+### Tutorial Outline
+
+1. [Participant](./tutorial_participant.html)
+2. [Spectator](./tutorial_spectator.html)
+3. [Controller](./tutorial_controller.html)
+4. [Rebalancing Algorithms](./tutorial_rebalance.html)
+5. [User-Defined Rebalancing](./tutorial_user_def_rebalancer.html)
+6. [State Machines](./tutorial_state.html)
+7. [Messaging](./tutorial_messaging.html)
+8. [Customized health check](./tutorial_health.html)
+9. [Throttling](./tutorial_throttling.html)
+10. [Application Property Store](./tutorial_propstore.html)
+11. [Admin Interface](./tutorial_admin.html)
+12. [YAML Cluster Setup](./tutorial_yaml.html)
+13. [Helix Agent (for non-JVM systems)](./tutorial_agent.html)
+14. [Task Framework](./tutorial_task_framework.html)
+
+### Preliminaries
+
+First, we need to set up the system. Let\'s walk through the steps in building a distributed system using Helix.
+
+#### Start ZooKeeper
+
+This starts a zookeeper in standalone mode. For production deployment, see [Apache ZooKeeper](http://zookeeper.apache.org) for instructions.
+
+```
+./start-standalone-zookeeper.sh 2199 &
+```
+
+#### Create a Cluster
+
+Creating a cluster will define the cluster in appropriate znodes on ZooKeeper.
+
+Using the Java API:
+
+```
+// Create setup tool instance
+// Note: ZK_ADDRESS is the host:port of Zookeeper
+String ZK_ADDRESS = "localhost:2199";
+admin = new ZKHelixAdmin(ZK_ADDRESS);
+
+String CLUSTER_NAME = "helix-demo";
+//Create cluster namespace in zookeeper
+admin.addCluster(CLUSTER_NAME);
+```
+
+OR
+
+Using the command-line interface:
+
+```
+./helix-admin.sh --zkSvr localhost:2199 --addCluster helix-demo
+```
+
+
+#### Configure the Nodes of the Cluster
+
+First we\'ll add new nodes to the cluster, then configure the nodes in the cluster. Each node in the cluster must be uniquely identifiable.
+The most commonly used convention is hostname:port.
+
+```
+String CLUSTER_NAME = "helix-demo";
+int NUM_NODES = 2;
+String hosts[] = new String[]{"localhost","localhost"};
+String ports[] = new String[]{7000,7001};
+for (int i = 0; i < NUM_NODES; i++)
+{
+ InstanceConfig instanceConfig = new InstanceConfig(hosts[i]+ "_" + ports[i]);
+ instanceConfig.setHostName(hosts[i]);
+ instanceConfig.setPort(ports[i]);
+ instanceConfig.setInstanceEnabled(true);
+
+ //Add additional system specific configuration if needed. These can be accessed during the node start up.
+ instanceConfig.getRecord().setSimpleField("key", "value");
+ admin.addInstance(CLUSTER_NAME, instanceConfig);
+}
+```
+
+#### Configure the Resource
+
+A __resource__ represents the actual task performed by the nodes. It can be a database, index, topic, queue or any other processing entity.
+A resource can be divided into many sub-parts known as __partitions__.
+
+
+##### Define the State Model and Constraints
+
+For scalability and fault tolerance, each partition can have one or more replicas.
+The __state model__ allows one to declare the system behavior by first enumerating the various STATES, and the TRANSITIONS between them.
+A simple model is ONLINE-OFFLINE where ONLINE means the task is active and OFFLINE means it\'s not active.
+You can also specify how many replicas must be in each state, these are known as __constraints__.
+For example, in a search system, one might need more than one node serving the same index to handle the load.
+
+The allowed states:
+
+* MASTER
+* SLAVE
+* OFFLINE
+
+The allowed transitions:
+
+* OFFLINE to SLAVE
+* SLAVE to OFFLINE
+* SLAVE to MASTER
+* MASTER to SLAVE
+
+The constraints:
+
+* no more than 1 MASTER per partition
+* the rest of the replicas should be slaves
+
+The following snippet shows how to declare the state model and constraints for the MASTER-SLAVE model.
+
+```
+StateModelDefinition.Builder builder = new StateModelDefinition.Builder(STATE_MODEL_NAME);
+
+// Add states and their rank to indicate priority. A lower rank corresponds to a higher priority
+builder.addState(MASTER, 1);
+builder.addState(SLAVE, 2);
+builder.addState(OFFLINE);
+
+// Set the initial state when the node starts
+builder.initialState(OFFLINE);
+
+// Add transitions between the states.
+builder.addTransition(OFFLINE, SLAVE);
+builder.addTransition(SLAVE, OFFLINE);
+builder.addTransition(SLAVE, MASTER);
+builder.addTransition(MASTER, SLAVE);
+
+// set constraints on states
+
+// static constraint: upper bound of 1 MASTER
+builder.upperBound(MASTER, 1);
+
+// dynamic constraint: R means it should be derived based on the replication factor for the cluster
+// this allows a different replication factor for each resource without
+// having to define a new state model
+
+builder.dynamicUpperBound(SLAVE, "R");
+
+StateModelDefinition statemodelDefinition = builder.build();
+admin.addStateModelDef(CLUSTER_NAME, STATE_MODEL_NAME, myStateModel);
+```
+
+##### Assigning Partitions to Nodes
+
+The final goal of Helix is to ensure that the constraints on the state model are satisfied.
+Helix does this by assigning a __state__ to a partition (such as MASTER, SLAVE), and placing it on a particular node.
+
+There are 3 assignment modes Helix can operate in:
+
+* FULL_AUTO: Helix decides the placement and state of a partition.
+* SEMI_AUTO: Application decides the placement but Helix decides the state of a partition.
+* CUSTOMIZED: Application controls the placement and state of a partition.
+
+For more information on the assignment modes, see the [Rebalancing Algorithms](./tutorial_rebalance.html) section of this tutorial.
+
+```
+String RESOURCE_NAME = "MyDB";
+int NUM_PARTITIONS = 6;
+STATE_MODEL_NAME = "MasterSlave";
+String MODE = "SEMI_AUTO";
+int NUM_REPLICAS = 2;
+
+admin.addResource(CLUSTER_NAME, RESOURCE_NAME, NUM_PARTITIONS, STATE_MODEL_NAME, MODE);
+admin.rebalance(CLUSTER_NAME, RESOURCE_NAME, NUM_REPLICAS);
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/index.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+<head>
+ <title>Helix 0.6.8 Documentation</title>
+</head>
+
+### Get Helix
+
+[Download](./download.html)
+
+[Building](./Building.html)
+
+[Release Notes](./releasenotes/release-0.6.8.html)
+
+### Hands-On
+
+[Quickstart](./Quickstart.html)
+
+[Tutorial](./Tutorial.html)
+
+[Javadocs](http://helix.apache.org/javadocs/0.6.8/index.html)
+
+### Recipes
+
+[Distributed lock manager](./recipes/lock_manager.html)
+
+[Rabbit MQ consumer group](./recipes/rabbitmq_consumer_group.html)
+
+[Rsync replicated file store](./recipes/rsync_replicated_file_store.html)
+
+[Service discovery](./recipes/service_discovery.html)
+
+[Distributed task DAG execution](./recipes/task_dag_execution.html)
+
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/recipes/lock_manager.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+Distributed Lock Manager
+------------------------
+Distributed locks are used to synchronize accesses shared resources. Most applications today use ZooKeeper to model distributed locks.
+
+The simplest way to model a lock using ZooKeeper is (See ZooKeeper leader recipe for an exact and more advanced solution)
+
+* Each process tries to create an emphemeral node
+* If the node is successfully created, the process acquires the lock
+* Otherwise, it will watch the ZNode and try to acquire the lock again if the current lock holder disappears
+
+This is good enough if there is only one lock. But in practice, an application will need many such locks. Distributing and managing the locks among difference process becomes challenging. Extending such a solution to many locks will result in:
+
+* Uneven distribution of locks among nodes; the node that starts first will acquire all the locks. Nodes that start later will be idle.
+* When a node fails, how the locks will be distributed among remaining nodes is not predicable.
+* When new nodes are added the current nodes don\'t relinquish the locks so that new nodes can acquire some locks
+
+In other words we want a system to satisfy the following requirements.
+
+* Distribute locks evenly among all nodes to get better hardware utilization
+* If a node fails, the locks that were acquired by that node should be evenly distributed among other nodes
+* If nodes are added, locks must be evenly re-distributed among nodes.
+
+Helix provides a simple and elegant solution to this problem. Simply specify the number of locks and Helix will ensure that above constraints are satisfied.
+
+To quickly see this working run the `lock-manager-demo` script where 12 locks are evenly distributed among three nodes, and when a node fails, the locks get re-distributed among remaining two nodes. Note that Helix does not re-shuffle the locks completely, instead it simply distributes the locks relinquished by dead node among 2 remaining nodes evenly.
+
+----------------------------------------------------------------------------------------
+
+### Short Version
+This version starts multiple threads within the same process to simulate a multi node deployment. Try the long version to get a better idea of how it works.
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+mvn clean install package -DskipTests
+cd recipes/distributed-lock-manager/target/distributed-lock-manager-pkg/bin
+chmod +x *
+./lock-manager-demo
+```
+
+#### Output
+
+```
+./lock-manager-demo
+STARTING localhost_12000
+STARTING localhost_12002
+STARTING localhost_12001
+STARTED localhost_12000
+STARTED localhost_12002
+STARTED localhost_12001
+localhost_12001 acquired lock:lock-group_3
+localhost_12000 acquired lock:lock-group_8
+localhost_12001 acquired lock:lock-group_2
+localhost_12001 acquired lock:lock-group_4
+localhost_12002 acquired lock:lock-group_1
+localhost_12002 acquired lock:lock-group_10
+localhost_12000 acquired lock:lock-group_7
+localhost_12001 acquired lock:lock-group_5
+localhost_12002 acquired lock:lock-group_11
+localhost_12000 acquired lock:lock-group_6
+localhost_12002 acquired lock:lock-group_0
+localhost_12000 acquired lock:lock-group_9
+lockName acquired By
+======================================
+lock-group_0 localhost_12002
+lock-group_1 localhost_12002
+lock-group_10 localhost_12002
+lock-group_11 localhost_12002
+lock-group_2 localhost_12001
+lock-group_3 localhost_12001
+lock-group_4 localhost_12001
+lock-group_5 localhost_12001
+lock-group_6 localhost_12000
+lock-group_7 localhost_12000
+lock-group_8 localhost_12000
+lock-group_9 localhost_12000
+Stopping localhost_12000
+localhost_12000 Interrupted
+localhost_12001 acquired lock:lock-group_9
+localhost_12001 acquired lock:lock-group_8
+localhost_12002 acquired lock:lock-group_6
+localhost_12002 acquired lock:lock-group_7
+lockName acquired By
+======================================
+lock-group_0 localhost_12002
+lock-group_1 localhost_12002
+lock-group_10 localhost_12002
+lock-group_11 localhost_12002
+lock-group_2 localhost_12001
+lock-group_3 localhost_12001
+lock-group_4 localhost_12001
+lock-group_5 localhost_12001
+lock-group_6 localhost_12002
+lock-group_7 localhost_12002
+lock-group_8 localhost_12001
+lock-group_9 localhost_12001
+
+```
+
+----------------------------------------------------------------------------------------
+
+### Long version
+This provides more details on how to setup the cluster and where to plugin application code.
+
+#### Start ZooKeeper
+
+```
+./start-standalone-zookeeper 2199
+```
+
+#### Create a Cluster
+
+```
+./helix-admin --zkSvr localhost:2199 --addCluster lock-manager-demo
+```
+
+#### Create a Lock Group
+
+Create a lock group and specify the number of locks in the lock group.
+
+```
+./helix-admin --zkSvr localhost:2199 --addResource lock-manager-demo lock-group 6 OnlineOffline --mode AUTO_REBALANCE
+```
+
+#### Start the Nodes
+
+Create a Lock class that handles the callbacks.
+
+```
+public class Lock extends StateModel {
+ private String lockName;
+
+ public Lock(String lockName) {
+ this.lockName = lockName;
+ }
+
+ public void lock(Message m, NotificationContext context) {
+ System.out.println(" acquired lock:"+ lockName );
+ }
+
+ public void release(Message m, NotificationContext context) {
+ System.out.println(" releasing lock:"+ lockName );
+ }
+
+}
+```
+
+and a LockFactory that creates Locks
+
+```
+public class LockFactory extends StateModelFactory<Lock> {
+ /* Instantiates the lock handler, one per lockName */
+ public Lock create(String lockName) {
+ return new Lock(lockName);
+ }
+}
+```
+
+At node start up, simply join the cluster and Helix will invoke the appropriate callbacks on the appropriate Lock instance. One can start any number of nodes and Helix detects that a new node has joined the cluster and re-distributes the locks automatically.
+
+```
+public class LockProcess {
+ public static void main(String args) {
+ String zkAddress= "localhost:2199";
+ String clusterName = "lock-manager-demo";
+ //Give a unique id to each process, most commonly used format hostname_port
+ String instanceName ="localhost_12000";
+ ZKHelixAdmin helixAdmin = new ZKHelixAdmin(zkAddress);
+ //configure the instance and provide some metadata
+ InstanceConfig config = new InstanceConfig(instanceName);
+ config.setHostName("localhost");
+ config.setPort("12000");
+ admin.addInstance(clusterName, config);
+ //join the cluster
+ HelixManager manager;
+ manager = HelixManagerFactory.getHelixManager(clusterName,
+ instanceName,
+ InstanceType.PARTICIPANT,
+ zkAddress);
+ manager.getStateMachineEngine().registerStateModelFactory("OnlineOffline", modelFactory);
+ manager.connect();
+ Thread.currentThread.join();
+ }
+}
+```
+
+#### Start the Controller
+
+The controller can be started either as a separate process or can be embedded within each node process
+
+##### Separate Process
+This is recommended when number of nodes in the cluster \> 100. For fault tolerance, you can run multiple controllers on different boxes.
+
+```
+./run-helix-controller --zkSvr localhost:2199 --cluster lock-manager-demo 2>&1 > /tmp/controller.log &
+```
+
+##### Embedded Within the Node Process
+This is recommended when the number of nodes in the cluster is less than 100. To start a controller from each process, simply add the following lines to MyClass
+
+```
+public class LockProcess {
+ public static void main(String args) {
+ String zkAddress= "localhost:2199";
+ String clusterName = "lock-manager-demo";
+ // .
+ // .
+ manager.connect();
+ HelixManager controller;
+ controller = HelixControllerMain.startHelixController(zkAddress,
+ clusterName,
+ "controller",
+ HelixControllerMain.STANDALONE);
+ Thread.currentThread.join();
+ }
+}
+```
http://git-wip-us.apache.org/repos/asf/helix/blob/09a54c8e/website/0.6.8/src/site/markdown/recipes/rabbitmq_consumer_group.md
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diff --git a/website/0.6.8/src/site/markdown/recipes/rabbitmq_consumer_group.md b/website/0.6.8/src/site/markdown/recipes/rabbitmq_consumer_group.md
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+<!---
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements. See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership. The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License. You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied. See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+
+RabbitMQ Consumer Group
+-----------------------
+
+[RabbitMQ](http://www.rabbitmq.com/) is well-known open source software the provides robust messaging for applications.
+
+One of the commonly implemented recipes using this software is a work queue. [http://www.rabbitmq.com/tutorials/tutorial-four-java.html](http://www.rabbitmq.com/tutorials/tutorial-four-java.html) describes the use case where
+
+* A producer sends a message with a routing key
+* The message is routed to the queue whose binding key exactly matches the routing key of the message
+* There are multiple consumers and each consumer is interested in processing only a subset of the messages by binding to the interested keys
+
+The example provided [here](http://www.rabbitmq.com/tutorials/tutorial-four-java.html) describes how multiple consumers can be started to process all the messages.
+
+While this works, in production systems one needs the following:
+
+* Ability to handle failures: when a consumer fails, another consumer must be started or the other consumers must start processing these messages that should have been processed by the failed consumer
+* When the existing consumers cannot keep up with the task generation rate, new consumers will be added. The tasks must be redistributed among all the consumers
+
+In this recipe, we demonstrate handling of consumer failures and new consumer additions using Helix.
+
+Mapping this usecase to Helix is pretty easy as the binding key/routing key is equivalent to a partition.
+
+Let's take an example. Lets say the queue has 6 partitions, and we have 2 consumers to process all the queues.
+What we want is all 6 queues to be evenly divided among 2 consumers.
+Eventually when the system scales, we add more consumers to keep up. This will make each consumer process tasks from 2 queues.
+Now let's say that a consumer failed, reducing the number of active consumers to 2. This means each consumer must process 3 queues.
+
+We showcase how such a dynamic application can be developed using Helix. Even though we use RabbitMQ as the pub/sub system one can extend this solution to other pub/sub systems.
+
+### Try It
+
+```
+git clone https://git-wip-us.apache.org/repos/asf/helix.git
+cd helix
+git checkout tags/helix-0.6.8
+mvn clean install package -DskipTests
+cd recipes/rabbitmq-consumer-group/bin
+chmod +x *
+export HELIX_PKG_ROOT=`pwd`/helix-core/target/helix-core-pkg
+export HELIX_RABBITMQ_ROOT=`pwd`/recipes/rabbitmq-consumer-group/
+chmod +x $HELIX_PKG_ROOT/bin/*
+chmod +x $HELIX_RABBITMQ_ROOT/bin/*
+```
+
+#### Install RabbitMQ
+
+Setting up RabbitMQ on a local box is straightforward. You can find the instructions here
+http://www.rabbitmq.com/download.html
+
+#### Start ZK
+
+Start ZooKeeper at port 2199
+
+```
+$HELIX_PKG_ROOT/bin/start-standalone-zookeeper 2199
+```
+
+#### Setup the Consumer Group Cluster
+
+This will setup the cluster by creating a "rabbitmq-consumer-group" cluster and adds a "topic" with "6" queues.
+
+```
+$HELIX_RABBITMQ_ROOT/bin/setup-cluster.sh localhost:2199
+```
+
+#### Add Consumers
+
+Start 2 consumers in 2 different terminals. Each consumer is given a unique ID.
+
+```
+//start-consumer.sh zookeeperAddress (e.g. localhost:2181) consumerId , rabbitmqServer (e.g. localhost)
+$HELIX_RABBITMQ_ROOT/bin/start-consumer.sh localhost:2199 0 localhost
+$HELIX_RABBITMQ_ROOT/bin/start-consumer.sh localhost:2199 1 localhost
+
+```
+
+#### Start the Helix Controller
+
+Now start a Helix controller that starts managing the "rabbitmq-consumer-group" cluster.
+
+```
+$HELIX_RABBITMQ_ROOT/bin/start-cluster-manager.sh localhost:2199
+```
+
+#### Send Messages to the Topic
+
+Start sending messages to the topic. This script randomly selects a routing key (1-6) and sends the message to topic.
+Based on the key, messages gets routed to the appropriate queue.
+
+```
+$HELIX_RABBITMQ_ROOT/bin/send-message.sh localhost 20
+```
+
+After running this, you should see all 20 messages being processed by 2 consumers.
+
+#### Add Another Consumer
+
+Once a new consumer is started, Helix detects it. In order to balance the load between 3 consumers, it deallocates 1 partition from the existing consumers and allocates it to the new consumer. We see that
+each consumer is now processing only 2 queues.
+Helix makes sure that old nodes are asked to stop consuming before the new consumer is asked to start consuming for a given partition. But the transitions for each partition can happen in parallel.
+
+```
+$HELIX_RABBITMQ_ROOT/bin/start-consumer.sh localhost:2199 2 localhost
+```
+
+Send messages again to the topic
+
+```
+$HELIX_RABBITMQ_ROOT/bin/send-message.sh localhost 100
+```
+
+You should see that messages are now received by all 3 consumers.
+
+#### Stop a Consumer
+
+In any terminal press CTRL^C and notice that Helix detects the consumer failure and distributes the 2 partitions that were processed by failed consumer to the remaining 2 active consumers.
+
+
+### How does this work?
+
+Find the entire code [here](https://git-wip-us.apache.org/repos/asf?p=helix.git;a=tree;f=recipes/rabbitmq-consumer-group/src/main/java/org/apache/helix/recipes/rabbitmq).
+
+#### Cluster Setup
+
+This step creates ZNode on ZooKeeper for the cluster and adds the state model. We use online offline state model since there is no need for other states. The consumer is either processing a queue or it is not.
+
+It creates a resource called "rabbitmq-consumer-group" with 6 partitions. The execution mode is set to AUTO_REBALANCE. This means that the Helix controls the assignment of partition to consumers and automatically distributes the partitions evenly among the active consumers. When a consumer is added or removed, it ensures that a minimum number of partitions are shuffled.
+
+```
+zkclient = new ZkClient(zkAddr, ZkClient.DEFAULT_SESSION_TIMEOUT,
+ ZkClient.DEFAULT_CONNECTION_TIMEOUT, new ZNRecordSerializer());
+ZKHelixAdmin admin = new ZKHelixAdmin(zkclient);
+
+// add cluster
+admin.addCluster(clusterName, true);
+
+// add state model definition
+StateModelConfigGenerator generator = new StateModelConfigGenerator();
+admin.addStateModelDef(clusterName, "OnlineOffline",
+ new StateModelDefinition(generator.generateConfigForOnlineOffline()));
+
+// add resource "topic" which has 6 partitions
+String resourceName = "rabbitmq-consumer-group";
+admin.addResource(clusterName, resourceName, 6, "OnlineOffline", "AUTO_REBALANCE");
+```
+
+### Starting the Consumers
+
+The only thing consumers need to know is the ZooKeeper address, cluster name and consumer ID. It does not need to know anything else.
+
+```
+_manager = HelixManagerFactory.getZKHelixManager(_clusterName,
+ _consumerId,
+ InstanceType.PARTICIPANT,
+ _zkAddr);
+
+StateMachineEngine stateMach = _manager.getStateMachineEngine();
+ConsumerStateModelFactory modelFactory =
+ new ConsumerStateModelFactory(_consumerId, _mqServer);
+stateMach.registerStateModelFactory("OnlineOffline", modelFactory);
+
+_manager.connect();
+```
+
+Once the consumer has registered the state model and the controller is started, the consumer starts getting callbacks (onBecomeOnlineFromOffline) for the partition it needs to host. All it needs to do as part of the callback is to start consuming messages from the appropriate queue. Similarly, when the controller deallocates a partitions from a consumer, it fires onBecomeOfflineFromOnline for the same partition.
+As a part of this transition, the consumer will stop consuming from a that queue.
+
+```
+@Transition(to = "ONLINE", from = "OFFLINE")
+public void onBecomeOnlineFromOffline(Message message, NotificationContext context) {
+ LOG.debug(_consumerId + " becomes ONLINE from OFFLINE for " + _partition);
+ if (_thread == null) {
+ LOG.debug("Starting ConsumerThread for " + _partition + "...");
+ _thread = new ConsumerThread(_partition, _mqServer, _consumerId);
+ _thread.start();
+ LOG.debug("Starting ConsumerThread for " + _partition + " done");
+
+ }
+}
+
+@Transition(to = "OFFLINE", from = "ONLINE")
+public void onBecomeOfflineFromOnline(Message message, NotificationContext context)
+ throws InterruptedException {
+ LOG.debug(_consumerId + " becomes OFFLINE from ONLINE for " + _partition);
+ if (_thread != null) {
+ LOG.debug("Stopping " + _consumerId + " for " + _partition + "...");
+ _thread.interrupt();
+ _thread.join(2000);
+ _thread = null;
+ LOG.debug("Stopping " + _consumerId + " for " + _partition + " done");
+ }
+}
+```