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Posted to commits@helix.apache.org by ka...@apache.org on 2014/01/02 22:53:03 UTC
[18/24] [HELIX-348] Simplify website layout
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/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/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/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>
-
-Get Helix
----------
-
-First, let\'s get Helix, either build it, or download.
-
-### Build
-
- git clone https://git-wip-us.apache.org/repos/asf/incubator-helix.git
- cd incubator-helix
- git checkout tags/helix-0.7.0-incubating
- ./build
- cd helix-core/target/helix-core-pkg/bin //This folder contains all the scripts used in following sections
- chmod +x *
-
-### Download
-
-Download the 0.7.0-incubating 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.
-
-#### First, get to the tools directory
-
-If you built the code
-
-```
-cd incubator-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 incubator-helix/helix-core/target/helix-core-pkg/bin
-./quickstart.sh
-```
-
-##### 2 nodes are set up and the partitions 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.
-
-##### A third node is added and the cluster 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.
-
-##### 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 the 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 info 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. (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
-
-##### Now we can 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). And the _ideal state_ 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 info of 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" : {
- "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> --listPartitionInfo <clusterName> <resource> <partition>
- ./helix-admin.sh --zkSvr localhost:2199 --listPartitionInfo MYCLUSTER myDB 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" : {
- "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" : {
- "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/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/Tutorial.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/Tutorial.md b/site-releases/0.7.0-incubating/src/site/markdown/Tutorial.md
deleted file mode 100644
index 081bc7a..0000000
--- a/site-releases/0.7.0-incubating/src/site/markdown/Tutorial.md
+++ /dev/null
@@ -1,290 +0,0 @@
-<!---
-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. [Logical Accessors](./tutorial_accessors.html)
-12. [Admin Interface](./tutorial_admin.html)
-13. [YAML Cluster Setup](./tutorial_yaml.html)
-
-### Preliminaries
-
-First, we need to set up the system. Let\'s walk through the steps in building a distributed system using Helix. We will show how to do this using both the Java admin interface, as well as the [cluster accessor](./tutorial_accessors.html) interface. You can choose either interface depending on which most closely matches your needs.
-
-### 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 accessor API:
-
-```
-// Note: ZK_ADDRESS is the host:port of Zookeeper
-String ZK_ADDRESS = "localhost:2199";
-HelixConnection connection = new ZKHelixConnection(ZK_ADDRESS);
-
-ClusterId clusterId = ClusterId.from("helix-demo");
-ClusterAccessor clusterAccessor = connection.createClusterAccessor(clusterId);
-ClusterConfig clusterConfig = new ClusterConfig.Builder(clusterId).build();
-clusterAccessor.createCluster(clusterConfig);
-```
-
-OR
-
-Using the HelixAdmin Java interface:
-
-```
-// Create setup tool instance
-// Note: ZK_ADDRESS is the host:port of Zookeeper
-String ZK_ADDRESS = "localhost:2199";
-HelixAdmin 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.
-
-```
-int NUM_NODES = 2;
-String hosts[] = new String[]{"localhost","localhost"};
-int ports[] = new int[]{7000,7001};
-for (int i = 0; i < NUM_NODES; i++)
-{
- ParticipantId participantId = ParticipantId.from(hosts[i] + "_" + ports[i]);
-
- // set additional configuration for the participant; these can be accessed during node start up
- UserConfig userConfig = new UserConfig(Scope.participant(participantId));
- userConfig.setSimpleField("key", "value");
-
- // configure and add the participant
- ParticipantConfig participantConfig = new ParticipantConfig.Builder(participantId)
- .hostName(hosts[i]).port(ports[i]).enabled(true).userConfig(userConfig).build();
- clusterAccessor.addParticipantToCluster(participantConfig);
-}
-```
-
-OR
-
-Using the HelixAdmin Java interface:
-
-```
-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();
-```
-
-Then, add the state model definition:
-
-```
-clusterAccessor.addStateModelDefinitionToCluster(stateModelDefinition);
-```
-
-OR
-
-```
-admin.addStateModelDef(CLUSTER_NAME, STATE_MODEL_NAME, stateModelDefinition);
-```
-
-#### 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 on
-
-* 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 info on the assignment modes, see [Rebalancing Algorithms](./tutorial_rebalance.html) section of the tutorial.
-
-Here is an example of adding the resource in SEMI_AUTO mode (i.e. locations of partitions are specified a priori):
-
-```
-int NUM_PARTITIONS = 6;
-int NUM_REPLICAS = 2;
-ResourceId resourceId = resourceId.from("MyDB");
-
-SemiAutoRebalancerContext context = new SemiAutoRebalancerContext.Builder(resourceId)
- .replicaCount(NUM_REPLICAS).addPartitions(NUM_PARTITIONS)
- .stateModelDefId(stateModelDefinition.getStateModelDefId())
- .addPreferenceList(partition1Id, preferenceList) // preferred locations of each partition
- // add other preference lists per partition
- .build();
-
-// or add all preference lists at once if desired (map of PartitionId to List of ParticipantId)
-context.setPreferenceLists(preferenceLists);
-
-// or generate a default set of preference lists given the set of all participants
-context.generateDefaultConfiguration(stateModelDefinition, participantIdSet);
-
-// add the resource to the cluster
-ResourceConfig resourceConfig = new ResourceConfig.Builder(resourceId)
- .rebalancerContext(context)
- .build();
-clusterAccessor.addResourceToCluster(resourceConfig);
-```
-
-OR
-
-```
-String RESOURCE_NAME = "MyDB";
-int NUM_PARTITIONS = 6;
-String MODE = "SEMI_AUTO";
-int NUM_REPLICAS = 2;
-
-admin.addResource(CLUSTER_NAME, RESOURCE_NAME, NUM_PARTITIONS, STATE_MODEL_NAME, MODE);
-
-// specify the preference lists yourself
-IdealState idealState = admin.getResourceIdealState(CLUSTER_NAME, RESOURCE_NAME);
-idealState.setPreferenceList(partitionId, preferenceList); // preferred locations of each partition
-// add other preference lists per partition
-
-// or add all preference lists at once if desired
-idealState.getRecord().setListFields(preferenceLists);
-admin.setResourceIdealState(CLUSTER_NAME, RESOURCE_NAME, idealState);
-
-// or generate a default set of preference lists
-admin.rebalance(CLUSTER_NAME, RESOURCE_NAME, NUM_REPLICAS);
-```
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/UseCases.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/UseCases.md b/site-releases/0.7.0-incubating/src/site/markdown/UseCases.md
deleted file mode 100644
index 001b012..0000000
--- a/site-releases/0.7.0-incubating/src/site/markdown/UseCases.md
+++ /dev/null
@@ -1,113 +0,0 @@
-<!---
-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>Use Cases</title>
-</head>
-
-
-# Use cases at LinkedIn
-
-At LinkedIn Helix framework is used to manage 3 distributed data systems which are quite different from each other.
-
-* Espresso
-* Databus
-* Search As A Service
-
-## Espresso
-
-Espresso is a distributed, timeline consistent, scal- able, document store that supports local secondary indexing and local transactions.
-Espresso databases are horizontally partitioned into a number of partitions, with each partition having a certain number of replicas
-distributed across the storage nodes.
-Espresso designates one replica of each partition as master and the rest as slaves; only one master may exist for each partition at any time.
-Espresso enforces timeline consistency where only the master of a partition can accept writes to its records, and all slaves receive and
-apply the same writes through a replication stream.
-For load balancing, both master and slave partitions are assigned evenly across all storage nodes.
-For fault tolerance, it adds the constraint that no two replicas of the same partition may be located on the same node.
-
-### State model
-Espresso follows a Master-Slave state model. A replica can be in Offline,Slave or Master state.
-The state machine table describes the next state given the Current State, Final State
-
-```
- OFFLINE | SLAVE | MASTER
- _____________________________
- | | | |
-OFFLINE | N/A | SLAVE | SLAVE |
- |__________|________|_________|
- | | | |
-SLAVE | OFFLINE | N/A | MASTER |
- |__________|________|_________|
- | | | |
-MASTER | SLAVE | SLAVE | N/A |
- |__________|________|_________|
-
-```
-
-### Constraints
-* Max number of replicas in Master state:1
-* Execution mode AUTO. i.e on node failure no new replicas will be created. Only the State of remaining replicas will be changed.
-* Number of mastered partitions on each node must be approximately same.
-* The above constraint must be satisfied when a node fails or a new node is added.
-* When new nodes are added the number of partitions moved must be minimized.
-* When new nodes are added the max number of OFFLINE-SLAVE transitions that can happen concurrently on new node is X.
-
-## Databus
-
-Databus is a change data capture (CDC) system that provides a common pipeline for transporting events
-from LinkedIn primary databases to caches within various applications.
-Databus deploys a cluster of relays that pull the change log from multiple databases and
-let consumers subscribe to the change log stream. Each Databus relay connects to one or more database servers and
-hosts a certain subset of databases (and partitions) from those database servers.
-
-For a large partitioned database (e.g. Espresso), the change log is consumed by a bank of consumers.
-Each databus partition is assigned to a consumer such that partitions are evenly distributed across consumers and each partition is
-assigned to exactly one consumer at a time. The set of consumers may grow over time, and consumers may leave the group due to planned or unplanned
-outages. In these cases, partitions must be reassigned, while maintaining balance and the single consumer-per-partition invariant.
-
-### State model
-Databus consumers follow a simple Offline-Online state model.
-The state machine table describes the next state given the Current State, Final State
-
-<pre><code>
- OFFLINE | ONLINE |
- ___________________|
- | | |
-OFFLINE | N/A | ONLINE |
- |__________|________|
- | | |
-ONLINE | OFFLINE | N/A |
- |__________|________|
-
-
-</code></pre>
-
-
-## Search As A Service
-
-LinkedIn�s Search-as-a-service lets internal customers define custom indexes on a chosen dataset
-and then makes those indexes searchable via a service API. The index service runs on a cluster of machines.
-The index is broken into partitions and each partition has a configured number of replicas.
-Each cluster server runs an instance of the Sensei system (an online index store) and hosts index partitions.
-Each new indexing service gets assigned to a set of servers, and the partition replicas must be evenly distributed across those servers.
-
-### State model
-
-
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/index.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/index.md b/site-releases/0.7.0-incubating/src/site/markdown/index.md
deleted file mode 100644
index 333110b..0000000
--- a/site-releases/0.7.0-incubating/src/site/markdown/index.md
+++ /dev/null
@@ -1,62 +0,0 @@
-<!---
-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>Home</title>
-</head>
-
-__Alpha!__ This release contains many new features, but things might not work just right, and some APIs are still in the process of being developed.
-
-Navigating the Documentation
-----------------------------
-
-### Conceptual Understanding
-
-[Concepts / Terminology](./Concepts.html)
-
-[Architecture](./Architecture.html)
-
-### Hands-on Helix
-
-[Getting Helix](./Building.html)
-
-[Quickstart](./Quickstart.html)
-
-[Tutorial](./Tutorial.html)
-
-[Javadocs](http://helix.incubator.apache.org/javadocs/0.7.0-incubating/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)
-
-[User-Defined Rebalancer Example](./recipes/user_def_rebalancer.html)
-
-### Download
-
-[0.7.0-incubating](./download.html)
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/recipes/lock_manager.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/recipes/lock_manager.md b/site-releases/0.7.0-incubating/src/site/markdown/recipes/lock_manager.md
deleted file mode 100644
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--- a/site-releases/0.7.0-incubating/src/site/markdown/recipes/lock_manager.md
+++ /dev/null
@@ -1,253 +0,0 @@
-<!---
-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 use Zookeeper to model the 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 can successfully create it then, it acquires the lock
-* Else it will watch on 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 lock. 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 dont 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 with in 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/incubator-helix.git
-cd incubator-helix
-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 FULL_AUTO
-```
-
-##### 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 );
- }
-
-}
-
-```
-
-LockFactory that creates the lock
-
-```
-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 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
-
-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/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/recipes/rabbitmq_consumer_group.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/recipes/rabbitmq_consumer_group.md b/site-releases/0.7.0-incubating/src/site/markdown/recipes/rabbitmq_consumer_group.md
deleted file mode 100644
index 9edc2cb..0000000
--- a/site-releases/0.7.0-incubating/src/site/markdown/recipes/rabbitmq_consumer_group.md
+++ /dev/null
@@ -1,227 +0,0 @@
-<!---
-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 a 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 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 consumers 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 which reduces the number of active consumers to 2. This means each consumer must process 3 queues.
-
-We showcase how such a dynamic App 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/incubator-helix.git
-cd incubator-helix
-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 $HELIX_RABBITMQ_ROOT/bin/*
-```
-
-
-Install Rabbit MQ
-----------------
-
-Setting up RabbitMQ on a local box is straightforward. You can find the instructions here
-http://www.rabbitmq.com/download.html
-
-Start ZK
---------
-Start zookeeper at port 2199
-
-```
-$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
-$HELIX_RABBITMQ_ROOT/bin/start-consumer.sh localhost:2199 1 localhost
-
-```
-
-Start HelixController
---------------------
-Now start a Helix controller that starts managing the "rabbitmq-consumer-group" cluster.
-
-```
-$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 it work
-================
-
-Find the entire code [here](https://git-wip-us.apache.org/repos/asf?p=incubator-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 FULL_AUTO. 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", "FULL_AUTO");
-```
-
-Starting the consumers
-----------------------
-The only thing consumers need to know is the zkaddress, 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 statemodel 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");
-
- }
- }
-```
\ No newline at end of file
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/439125ae/site-releases/0.7.0-incubating/src/site/markdown/recipes/rsync_replicated_file_store.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/recipes/rsync_replicated_file_store.md b/site-releases/0.7.0-incubating/src/site/markdown/recipes/rsync_replicated_file_store.md
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--- a/site-releases/0.7.0-incubating/src/site/markdown/recipes/rsync_replicated_file_store.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.
--->
-
-Near real time rsync replicated file system
-===========================================
-
-Quickdemo
----------
-
-* 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 master are replicated to the slaves automatically. In this demo, a.txt and b.txt are written to ```/tmp/localhost_12001/filestore``` and it gets 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 appears in ```/tmp/localhost_12003/filestore```
-* Ignore the interrupted exceptions on the console :-).
-
-
-```
-git clone https://git-wip-us.apache.org/repos/asf/incubator-helix.git
-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 usecases is also that files are typically only added or deleted, rarely updated. When there are updates, they are rare and do not have any concurrency requirements.
-
-These are much simpler requirements than what general purpose distributed file system have to satisfy including concurrent access to files, random access for reads and updates, posix compliance etc. 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 the 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, 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.
-Sequence gets incremented on every transaction and and generation is increment when a new master is elected.
-
-### Replication
-
-Replication is required to slave to keep up with the 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.
-
-
-### Fail over
-
-When a master fails, a new slave will be promoted to master. If the prev master node is reachable, then the new master will flush all the
-changes from previous master before taking up mastership. The new master will record the end transaction id of the current generation and then starts new generation
-with sequence starting from 1. After this the master will begin accepting writes.
-
-
-
-
-
-
-Rsync based solution
--------------------
-
-
-
-
-This application demonstrate a file store that uses rsync as the replication mechanism. One can envision a similar system where instead of using rsync,
-can implement a custom solution to notify the slave of the changes and also provide an api to pull the change files.
-#### Concept
-* 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 support file uploads and downloads and writes the files to ```file_store_dir```. This is not included in this application. Idea is that most applications have different ways of implementing this component and has some business logic associated with it. 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 File System 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 notification 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.
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