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Posted to commits@helix.apache.org by ka...@apache.org on 2014/01/02 01:14:04 UTC
[04/31] Redesign documentation for 0.6.2, 0.7.0, and trunk
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_admin.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_admin.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_admin.md
index 3285ad9..90ee77c 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_admin.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_admin.md
@@ -21,45 +21,46 @@ under the License.
<title>Tutorial - Admin Operations</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Admin Operations
+## [Helix Tutorial](./Tutorial.html): Admin Operations
-Helix provides a set of admin api for cluster management operations. They are supported via:
+Helix provides a set of admin APIs for cluster management operations. They are supported via:
-* _Java API_
-* _Commandline interface_
-* _REST interface via helix-admin-webapp_
+* Java API
+* Command Line Interface
+* REST Interface via helix-admin-webapp
### Java API
See interface [_org.apache.helix.HelixAdmin_](http://helix.incubator.apache.org/javadocs/0.7.0-incubating/reference/org/apache/helix/HelixAdmin.html)
-### Command-line interface
-The command-line tool comes with helix-core package:
+### Command Line Interface
+The command line tool comes with helix-core package:
-Get the command-line tool:
+Get the command line tool:
-```
- - git clone https://git-wip-us.apache.org/repos/asf/incubator-helix.git
- - cd incubator-helix
- - ./build
- - cd helix-core/target/helix-core-pkg/bin
- - chmod +x *.sh
+```
+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
+chmod +x *.sh
```
Get help:
```
- - ./helix-admin.sh --help
+./helix-admin.sh --help
```
All other commands have this form:
```
- ./helix-admin.sh --zkSvr <ZookeeperServerAddress> <command> <parameters>
+./helix-admin.sh --zkSvr <ZookeeperServerAddress> <command> <parameters>
```
-Admin commands and brief description:
+#### Supported Commands
-| Command syntax | Description |
+| Command Syntax | Description |
| -------------- | ----------- |
| _\-\-activateCluster \<clusterName controllerCluster true/false\>_ | Enable/disable a cluster in distributed controller mode |
| _\-\-addCluster \<clusterName\>_ | Add a new cluster |
@@ -102,17 +103,18 @@ Admin commands and brief description:
| _\-\-swapInstance \<clusterName oldInstance newInstance\>_ | Swap an old instance with a new instance |
| _\-\-zkSvr \<ZookeeperServerAddress\>_ | Provide zookeeper address |
-### REST interface
+### REST Interface
The REST interface comes wit helix-admin-webapp package:
-```
- - git clone https://git-wip-us.apache.org/repos/asf/incubator-helix.git
- - cd incubator-helix
- - ./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
+```
+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-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
@@ -121,75 +123,75 @@ The REST interface comes wit helix-admin-webapp package:
* List all clusters
```
- curl http://localhost:8100/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
+ 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
+ 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
+ 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
+ curl -X DELETE http://localhost:8100/clusters/MyCluster
```
-
+
* _/clusters/{clusterName}/resourceGroups_
* List all resources in a cluster
-
+
```
- curl http://localhost:8100/clusters/MyCluster/resourceGroups
+ 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
+ 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
+ curl http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB
```
-
+
* Drop a resource
-
+
```
- curl -X DELETE http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB
+ 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
+ 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
+ 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"
@@ -215,193 +217,192 @@ The REST interface comes wit helix-admin-webapp package:
> 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
+ 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
+ curl http://localhost:8100/clusters/MyCluster/resourceGroups/MyDB/externalView
```
* _/clusters/{clusterName}/instances_
* List all instances
-
+
```
- curl http://localhost:8100/clusters/MyCluster/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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ 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
+ curl http://localhost:8100/zkPath/MyCluster
```
* _/clusters/{clusterName}/StateModelDefs_
* Show all state model definitions
-
+
```
- curl http://localhost:8100/clusters/MyCluster/StateModelDefs
+ 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"
- }
- }
+
+ ```
+ 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
+ }
+ }
+ > 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
+ curl http://localhost:8100/clusters/MyCluster/StateModelDefs/OnlineOffline
```
* _/clusters/{clusterName}/constraints/{constraintType}_
* Show all contraints
-
+
```
- curl http://localhost:8100/clusters/MyCluster/constraints/MESSAGE_CONSTRAINT
+ 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
+ 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
+ curl -X DELETE http://localhost:8100/clusters/MyCluster/constraints/MESSAGE_CONSTRAINT/MyConstraint
```
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_controller.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_controller.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_controller.md
index 1a4cc45..0957c39 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_controller.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_controller.md
@@ -21,18 +21,17 @@ under the License.
<title>Tutorial - Controller</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Controller
+## [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 the Helix Agent
-
+### Start the Helix Controller
It requires the following parameters:
-
+
* clusterId: A logical ID to represent the group of nodes
* controllerId: A logical ID of the process creating the controller instance. Generally this is host:port.
-* zkConnectString: Connection string to Zookeeper. This is of the form host1:port1,host2:port2,host3:port3.
+* zkConnectString: Connection string to Zookeeper. This is of the form host1:port1,host2:port2,host3:port3.
```
HelixConnection connection = new ZKHelixConnection(zkConnectString);
@@ -50,13 +49,13 @@ HelixController controller = connection.createController(clusterId, controllerId
controller.startAsync();
```
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
+### Controller Deployment Modes
Helix provides multiple options to deploy the controller.
@@ -72,7 +71,7 @@ If setting up a separate controller process is not viable, then it is possible t
#### 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.
+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/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_health.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_health.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_health.md
index e1a7f3c..03b1dcc 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_health.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_health.md
@@ -21,15 +21,15 @@ under the License.
<title>Tutorial - Customizing Heath Checks</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Customizing Health Checks
+## [Helix Tutorial](./Tutorial.html): Customizing Health Checks
-In this chapter, we\'ll learn how to customize the health check, based on metrics of your distributed system.
+In this chapter, we\'ll learn how to customize health checks based on metrics of your distributed system.
### Health Checks
Note: _this in currently in development mode, not yet ready for production._
-Helix provides the ability for each node in the system to report health metrics on a periodic basis.
+Helix provides the ability for each node in the system to report health metrics on a periodic basis.
Helix supports multiple ways to aggregate these metrics:
@@ -40,7 +40,7 @@ Helix supports multiple ways to aggregate these metrics:
Helix persists the aggregated value only.
-Applications can define a threshold on the aggregate values according to the SLAs, and when the SLA is violated Helix will fire an alert.
+Applications can define a threshold on the aggregate values according to the SLAs, and when the SLA is violated Helix will fire an alert.
Currently Helix only fires an alert, but in a future release we plan to use these metrics to either mark the node dead or load balance the partitions.
This feature will be valuable for distributed systems that support multi-tenancy and have a large variation in work load patterns. In addition, this can be used to detect skewed partitions (hotspots) and rebalance the cluster.
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_messaging.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_messaging.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_messaging.md
index f65ce7c..bf22d05 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_messaging.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_messaging.md
@@ -21,51 +21,50 @@ under the License.
<title>Tutorial - Messaging</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Messaging
+## [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 which is quite useful in practice. It is common that nodes in a distributed system require a mechanism to interact with each other.
+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. Helix 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 appropriate nodes. Once the nodes respond, Helix provides the bootstrapping replica with all the responses.
+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);
+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 [Javadocs](http://helix.incubator.apache.org/javadocs/0.7.0-incubating/reference/org/apache/helix/messaging/DefaultMessagingService.html) for more info.
-
+See HelixManager.DefaultMessagingService in the [Javadocs](http://helix.incubator.apache.org/javadocs/0.7.0-incubating/reference/org/apache/helix/messaging/DefaultMessagingService.html) for more information.
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_participant.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_participant.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_participant.md
index da55cbd..fcda1ec 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_participant.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_participant.md
@@ -21,28 +21,28 @@ under the License.
<title>Tutorial - Participant</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Participant
+## [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.
+In this chapter, we\'ll learn how to implement a __Participant__, which is a primary functional component of a distributed system.
-### Start the Helix Agent
+### Start the Helix Participant
-The Helix agent is a common component that connects each system component with the controller.
+The Helix participant class is a common component that connects each participant with the controller.
It requires the following parameters:
-
+
* clusterId: A logical ID to represent the group of nodes
* participantId: A logical ID of the process creating the manager instance. Generally this is host:port.
-* zkConnectString: Connection string to Zookeeper. This is of the form host1:port1,host2:port2,host3:port3.
+* zkConnectString: Connection string to Zookeeper. This is of the form host1:port1,host2:port2,host3:port3.
-After the Helix participant instance is created, only thing that needs to be registered is the state model factory.
+After the Helix participant instance is created, 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
-* _An application defined state model factory_
+* _An application-defined state model factory_
```
@@ -50,8 +50,8 @@ HelixConnection connection = new ZKHelixConnection(zkConnectString);
HelixParticipant participant = connection.createParticipant(clusterId, participantId);
StateMachineEngine stateMach = participant.getStateMachineEngine();
-// create a stateModelFactory that returns a statemodel object for each partition.
-StateModelFactory<StateModel> stateModelFactory = new OnlineOfflineStateModelFactory();
+// create a stateModelFactory that returns a statemodel object for each partition.
+HelixStateModelFactory<OnlineOfflineStateModel> stateModelFactory = new OnlineOfflineStateModelFactory();
stateMach.registerStateModelFactory(stateModelType, stateModelFactory);
participant.startAsync();
```
@@ -59,38 +59,37 @@ participant.startAsync();
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> {
+public class OnlineOfflineStateModelFactory extends HelixStateModelFactory<OnlineOfflineStateModel> {
@Override
- public StateModel createNewStateModel(String stateUnitKey) {
+ public OnlineOfflineStateModel createNewStateModel(PartitionId partitionId) {
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()");
+@StateModelInfo(states = "{'OFFLINE','ONLINE'}", initialState = "OFFINE")
+public static class OnlineOfflineStateModel extends StateModel {
+ @Transition(from = "OFFLINE", to = "ONLINE")
+ public void onBecomeOnlineFromOffline(Message message,
+ NotificationContext context) {
- ////////////////////////////////////////////////////////////////////////////////////////////////
- // Application logic to handle transition //
- // For example, you might start a service, run initialization, etc //
- ////////////////////////////////////////////////////////////////////////////////////////////////
- }
+ System.out.println("OnlineOfflineStateModel.onBecomeOnlineFromOffline()");
- @Transition(from = "ONLINE", to = "OFFLINE")
- public void onBecomeOfflineFromOnline(Message message,
- NotificationContext context) {
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ // Application logic to handle transition //
+ // For example, you might start a service, run initialization, etc //
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ }
- System.out.println("OnlineOfflineStateModel.onBecomeOfflineFromOnline()");
+ @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 //
- ////////////////////////////////////////////////////////////////////////////////////////////////
- }
+ ////////////////////////////////////////////////////////////////////////////////////////////////
+ // 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/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_propstore.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_propstore.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_propstore.md
index 41bcc69..5e9d8b6 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_propstore.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_propstore.md
@@ -21,14 +21,14 @@ under the License.
<title>Tutorial - Application Property Store</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Application Property Store
+## [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.
+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 and a write-through cache. This is far more efficient than reading from Zookeeper for every access.
+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.incubator.apache.org/javadocs/0.7.0-incubating/reference/org/apache/helix/store/package-summary.html) for details.
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_rebalance.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_rebalance.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_rebalance.md
index 8f42a5a..8599542 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_rebalance.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_rebalance.md
@@ -21,7 +21,7 @@ under the License.
<title>Tutorial - Rebalancing Algorithms</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Rebalancing Algorithms
+## [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.
@@ -55,7 +55,7 @@ Helix has four options for rebalancing, in increasing order of customization by
### 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.
+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.
@@ -105,10 +105,10 @@ If there are 3 nodes in the cluster, then Helix will balance the masters and sla
}
```
-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..
+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
+### SEMI_AUTO
When the application needs to control the placement of the replicas, use the SEMI_AUTO rebalance mode.
@@ -135,11 +135,11 @@ Example: In the ideal state below, the partition \'MyResource_0\' is constrained
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.
+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
+### 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.
+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:
@@ -170,12 +170,12 @@ Here\'s an example, again with 3 partitions, 2 replicas per partition, and the M
}
```
-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.
+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
+### 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
+### 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/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_spectator.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_spectator.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_spectator.md
index 24c1cf4..e43cd6b 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_spectator.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_spectator.md
@@ -21,46 +21,46 @@ under the License.
<title>Tutorial - Spectator</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Spectator
+## [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.
+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 the Helix agent
+### Start a Connection
-Same as for a Participant, The Helix agent is the common component that connects each system component with the controller.
+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.
+* 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.
+ * 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, only thing that needs to be registered is the listener. When the ExternalView changes, the listener is notified.
-
-### Spectator Code
+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.PARTICIPANT,
- zkConnectString);
+ 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(, "PARTITION_NAME", "PARTITION_STATE");
instances = routingTableProvider.getInstances("myDB", "myDB_1", "ONLINE");
////////////////////////////////////////////////////////////////////////////////////////////////
@@ -72,5 +72,4 @@ result = theInstance.sendRequest(yourApplicationRequest, responseObject);
```
-When the external view changes, the application needs to react by sending requests to a different instance.
-
+When the external view changes, the application needs to react by sending requests to a different instance.
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_state.md
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diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_state.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_state.md
index 4f7b1b5..9fd0f9f 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_state.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_state.md
@@ -21,31 +21,31 @@ under the License.
<title>Tutorial - State Machine Configuration</title>
</head>
-# [Helix Tutorial](./Tutorial.html): State Machine Configuration
+## [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
+### State Models
-Helix comes with 3 default state models that are commonly used. It is possible to have multiple state models in a cluster.
+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
+#### 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
+#### ONLINE-OFFLINE
* Has 2 states: OFFLINE and ONLINE. This simple state model is a good starting point for most applications.
-### LEADER-STANDBY
+#### 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
+### Constraints
In addition to the state machine configuration, one can specify the constraints of states and transitions.
@@ -54,38 +54,40 @@ For example, one can say:
* MASTER:1
<br/>Maximum number of replicas in MASTER state at any time is 1
-* OFFLINE-SLAVE:5
+* 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
+#### 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
+#### 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
+#### 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
+### Special States
-### DROPPED
+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
+#### 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
+### 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.
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_throttling.md
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diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_throttling.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_throttling.md
index 7417979..16a6f81 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_throttling.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_throttling.md
@@ -21,13 +21,13 @@ under the License.
<title>Tutorial - Throttling</title>
</head>
-# [Helix Tutorial](./Tutorial.html): Throttling
+## [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 is capable of coordinating this decision.
+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 light weight, but some might involve moving data, which is quite expensive from a network and IOPS perspective.
+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:
@@ -36,3 +36,4 @@ Helix allows applications to set a threshold on transitions. The threshold can b
* Resource e.g database
* Node i.e per-node maximum transitions in parallel
+
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_user_def_rebalancer.md
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diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_user_def_rebalancer.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_user_def_rebalancer.md
index f30aafc..90577af 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_user_def_rebalancer.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_user_def_rebalancer.md
@@ -21,7 +21,7 @@ under the License.
<title>Tutorial - User-Defined Rebalancing</title>
</head>
-# [Helix Tutorial](./Tutorial.html): User-Defined Rebalancing
+## [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.
@@ -224,4 +224,4 @@ On any node failure, as in the case of node addition, the rebalancer is invoked
The rebalancer was invoked once again and the resulting ResourceAssignment reflects the steady state.
### Caveats
-- The rebalancer class must be available at runtime, or else Helix will not attempt to rebalance at all
\ No newline at end of file
+- The rebalancer class must be available at runtime, or else Helix will not attempt to rebalance at all
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/markdown/tutorial_yaml.md
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_yaml.md b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_yaml.md
index 0f8e0cc..4660afa 100644
--- a/site-releases/0.7.0-incubating/src/site/markdown/tutorial_yaml.md
+++ b/site-releases/0.7.0-incubating/src/site/markdown/tutorial_yaml.md
@@ -21,7 +21,7 @@ under the License.
<title>Tutorial - YAML Cluster Setup</title>
</head>
-# [Helix Tutorial](./Tutorial.html): YAML Cluster Setup
+## [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.
@@ -99,4 +99,4 @@ 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.
\ No newline at end of file
+- 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/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/resources/images/HELIX-components.png
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http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/site.xml
----------------------------------------------------------------------
diff --git a/site-releases/0.7.0-incubating/src/site/site.xml b/site-releases/0.7.0-incubating/src/site/site.xml
index 4003197..af84d98 100644
--- a/site-releases/0.7.0-incubating/src/site/site.xml
+++ b/site-releases/0.7.0-incubating/src/site/site.xml
@@ -17,12 +17,12 @@
-->
<project name="Apache Helix">
<bannerLeft>
- <src>images/helix-logo.jpg</src>
- <href>http://helix.incubator.apache.org/site-releases/0.7.0-incubating-site</href>
+ <src>../../images/helix-logo.jpg</src>
+ <href>http://helix.incubator.apache.org/</href>
</bannerLeft>
<bannerRight>
- <src>http://incubator.apache.org/images/egg-logo.png</src>
- <href>http://incubator.apache.org/</href>
+ <src>../../images/feather_small.gif</src>
+ <href>http://www.apache.org/</href>
</bannerRight>
<version position="none"/>
@@ -58,19 +58,20 @@
<item name="Release 0.7.0-incubating" href="http://helix.incubator.apache.org/site-releases/0.7.0-incubating-site/"/>
</breadcrumbs>
- <menu name="Apache Helix">
- <item name="Home" href="../../index.html"/>
+ <links>
+ <item name="Helix 0.7.0-incubating" 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-0.7.0-incubating.html"/>
</menu>
- <menu name="Helix 0.7.0-incubating">
- <item name="Introduction" href="./index.html"/>
- <item name="Getting Helix" href="./Building.html"/>
- <item name="Core concepts" href="./Concepts.html"/>
- <item name="Architecture" href="./Architecture.html"/>
+ <menu name="Hands-On">
<item name="Quick Start" href="./Quickstart.html"/>
<item name="Tutorial" href="./Tutorial.html"/>
- <item name="Release Notes" href="releasenotes/release-0.7.0-incubating.html"/>
- <item name="Download" href="./download.html"/>
+ <item name="Javadocs" href="http://helix.incubator.apache.org/javadocs/0.7.0-incubating"/>
</menu>
<menu name="Recipes">
@@ -104,9 +105,29 @@
</body>
<custom>
- <fluidoSkin>
+ <reflowSkin>
+ <theme>bootswatch-cerulean</theme>
+ <highlightJs>false</highlightJs>
+ <brand>
+ <name>Apache Helix</name>
+ <href>http://helix.incubator.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>
- <!-- twitter link work only with sidebar disabled -->
<sideBarEnabled>true</sideBarEnabled>
<googleSearch></googleSearch>
<twitter>
@@ -114,7 +135,7 @@
<showUser>true</showUser>
<showFollowers>false</showFollowers>
</twitter>
- </fluidoSkin>
+ </fluidoSkin-->
</custom>
</project>
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/0.7.0-incubating/src/site/xdoc/download.xml.vm
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diff --git a/site-releases/0.7.0-incubating/src/site/xdoc/download.xml.vm b/site-releases/0.7.0-incubating/src/site/xdoc/download.xml.vm
index 14e22c5..6949719 100644
--- a/site-releases/0.7.0-incubating/src/site/xdoc/download.xml.vm
+++ b/site-releases/0.7.0-incubating/src/site/xdoc/download.xml.vm
@@ -24,7 +24,7 @@ under the License.
xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
<properties>
- <title>Apache Incubator Helix Downloads</title>
+ <title>Apache Helix Downloads</title>
<author email="dev@helix.incubator.apache.org">Apache Helix Documentation Team</author>
</properties>
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/trunk/src/site/apt/releasing.apt
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diff --git a/site-releases/trunk/src/site/apt/releasing.apt b/site-releases/trunk/src/site/apt/releasing.apt
deleted file mode 100644
index 11d0cd9..0000000
--- a/site-releases/trunk/src/site/apt/releasing.apt
+++ /dev/null
@@ -1,107 +0,0 @@
- -----
- Helix release process
- -----
- -----
- 2012-12-15
- -----
-
-~~ 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
-
-Helix release process
-
- [[1]] Post to the dev list a few days before you plan to do an Helix release
-
- [[2]] Your maven setting must contains the entry to be able to deploy.
-
- ~/.m2/settings.xml
-
-+-------------
- <server>
- <id>apache.releases.https</id>
- <username></username>
- <password></password>
- </server>
-+-------------
-
- [[3]] Apache DAV passwords
-
-+-------------
- Add the following info into your ~/.netrc
- machine git-wip-us.apache.org login <apache username> <password>
-
-+-------------
- [[4]] Release Helix
- You should have a GPG agent running in the session you will run the maven release commands(preferred), and confirm it works by running "gpg -ab" (type some text and press Ctrl-D).
- If you do not have a GPG agent running, make sure that you have the "apache-release" profile set in your settings.xml as shown below.
-
- Run the release
-
-+-------------
-mvn release:prepare release:perform -B
-+-------------
-
- GPG configuration in maven settings xml:
-
-+-------------
-<profile>
- <id>apache-release</id>
- <properties>
- <gpg.passphrase>[GPG_PASSWORD]</gpg.passphrase>
- </properties>
-</profile>
-+-------------
-
- [[4]] go to https://repository.apache.org and close your staged repository. Note the repository url (format https://repository.apache.org/content/repositories/orgapachehelix-019/org/apache/helix/helix/0.6-incubating/)
-
-+-------------
-svn co https://dist.apache.org/repos/dist/dev/incubator/helix helix-dev-release
-cd helix-dev-release
-sh ./release-script-svn.sh version stagingRepoUrl
-then svn add <new directory created with new version as name>
-then svn ci
-+-------------
-
- [[5]] Validating the release
-
-+-------------
- * Download sources, extract, build and run tests - mvn clean package
- * Verify license headers - mvn -Prat -DskipTests
- * Download binaries and .asc files
- * Download release manager's public key - From the KEYS file, get the release manager's public key finger print and run gpg --keyserver pgpkeys.mit.edu --recv-key <key>
- * Validate authenticity of key - run gpg --fingerprint <key>
- * Check signatures of all the binaries using gpg <binary>
-+-------------
-
- [[6]] Call for a vote in the dev list and wait for 72 hrs. for the vote results. 3 binding votes are necessary for the release to be finalized. example
- After the vote has passed, move the files from dist dev to dist release: svn mv https://dist.apache.org/repos/dist/dev/incubator/helix/version to https://dist.apache.org/repos/dist/release/incubator/helix/
-
- [[7]] Prepare release note. Add a page in src/site/apt/releasenotes/ and change value of \<currentRelease> in parent pom.
-
-
- [[8]] Send out an announcement of the release to:
-
- * users@helix.incubator.apache.org
-
- * dev@helix.incubator.apache.org
-
- [[9]] Celebrate !
-
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/trunk/src/site/markdown/Architecture.md
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diff --git a/site-releases/trunk/src/site/markdown/Architecture.md b/site-releases/trunk/src/site/markdown/Architecture.md
deleted file mode 100644
index 933e917..0000000
--- a/site-releases/trunk/src/site/markdown/Architecture.md
+++ /dev/null
@@ -1,252 +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>Architecture</title>
-</head>
-
-Architecture
-----------------------------
-Helix aims to provide the following abilities to a distributed system:
-
-* Automatic management of a cluster hosting partitioned, replicated resources.
-* Soft and hard failure detection and handling.
-* Automatic load balancing via smart placement of resources on servers(nodes) based on server capacity and resource profile (size of partition, access patterns, etc).
-* Centralized config management and self discovery. Eliminates the need to modify config on each node.
-* Fault tolerance and optimized rebalancing during cluster expansion.
-* Manages entire operational lifecycle of a node. Addition, start, stop, enable/disable without downtime.
-* Monitor cluster health and provide alerts on SLA violation.
-* Service discovery mechanism to route requests.
-
-To build such a system, we need a mechanism to co-ordinate between different nodes and other components in the system. This mechanism can be achieved with software that reacts to any change in the cluster and comes up with a set of tasks needed to bring the cluster to a stable state. The set of tasks will be assigned to one or more nodes in the cluster. Helix serves this purpose of managing the various components in the cluster.
-
-
-
-Distributed System Components
-
-In general any distributed system cluster will have the following components and properties:
-
-* A set of nodes also referred to as instances.
-* A set of resources which can be databases, lucene indexes or tasks.
-* Each resource is also partitioned into one or more Partitions.
-* Each partition may have one or more copies called replicas.
-* Each replica can have a state associated with it. For example Master, Slave, Leader, Standby, Online, Offline etc
-
-Roles
------
-
-
-
-Not all nodes in a distributed system will perform similar functionalities. For example, a few nodes might be serving requests and a few nodes might be sending requests, and some nodes might be controlling the nodes in the cluster. Thus, Helix categorizes nodes by their specific roles in the system.
-
-We have divided Helix nodes into 3 logical components based on their responsibilities:
-
-1. Participant: The nodes that actually host the distributed resources.
-2. Spectator: The nodes that simply observe the Participant state and route the request accordingly. Routers, for example, need to know the instance on which a partition is hosted and its state in order to route the request to the appropriate end point.
-3. Controller: The controller observes and controls the Participant nodes. It is responsible for coordinating all transitions in the cluster and ensuring that state constraints are satisfied and cluster stability is maintained.
-
-These are simply logical components and can be deployed as per the system requirements. For example:
-
-1. The controller can be deployed as a separate service
-2. The controller can be deployed along with a Participant but only one Controller will be active at any given time.
-
-Both have pros and cons, which will be discussed later and one can chose the mode of deployment as per system needs.
-
-
-## Cluster state metadata store
-
-We need a distributed store to maintain the state of the cluster and a notification system to notify if there is any change in the cluster state. Helix uses Zookeeper to achieve this functionality.
-
-Zookeeper provides:
-
-* A way to represent PERSISTENT state which basically remains until its deleted.
-* A way to represent TRANSIENT/EPHEMERAL state which vanishes when the process that created the state dies.
-* Notification mechanism when there is a change in PERSISTENT and EPHEMERAL state
-
-The namespace provided by ZooKeeper is much like that of a standard file system. A name is a sequence of path elements separated by a slash (/). Every node[ZNode] in ZooKeeper\'s namespace is identified by a path.
-
-More info on Zookeeper can be found at http://zookeeper.apache.org
-
-## State machine and constraints
-
-Even though the concepts of Resources, Partitions, and Replicas are common to most distributed systems, one thing that differentiates one distributed system from another is the way each partition is assigned a state and the constraints on each state.
-
-For example:
-
-1. If a system is serving read-only data then all partition\'s replicas are equal and they can either be ONLINE or OFFLINE.
-2. If a system takes _both_ reads and writes but ensure that writes go through only one partition, the states will be MASTER, SLAVE, and OFFLINE. Writes go through the MASTER and replicate to the SLAVEs. Optionally, reads can go through SLAVES.
-
-Apart from defining state for each partition, the transition path to each state can be application specific. For example, in order to become MASTER it might be a requirement to first become a SLAVE. This ensures that if the SLAVE does not have the data as part of OFFLINE-SLAVE transition it can bootstrap data from other nodes in the system.
-
-Helix provides a way to configure an application specific state machine along with constraints on each state. Along with constraints on STATE, Helix also provides a way to specify constraints on transitions. (More on this later.)
-
-```
- OFFLINE | SLAVE | MASTER
- _____________________________
- | | | |
-OFFLINE | N/A | SLAVE | SLAVE |
- |__________|________|_________|
- | | | |
-SLAVE | OFFLINE | N/A | MASTER |
- |__________|________|_________|
- | | | |
-MASTER | SLAVE | SLAVE | N/A |
- |__________|________|_________|
-
-```
-
-
-
-## Concepts
-
-The following terminologies are used in Helix to model a state machine.
-
-* IdealState: The state in which we need the cluster to be in if all nodes are up and running. In other words, all state constraints are satisfied.
-* CurrentState: Represents the actual current state of each node in the cluster
-* ExternalView: Represents the combined view of CurrentState of all nodes.
-
-The goal of Helix is always to make the CurrentState of the system same as the IdealState. Some scenarios where this may not be true are:
-
-* When all nodes are down
-* When one or more nodes fail
-* New nodes are added and the partitions need to be reassigned
-
-### IdealState
-
-Helix lets the application define the IdealState on a resource basis which basically consists of:
-
-* List of partitions. Example: 64
-* Number of replicas for each partition. Example: 3
-* Node and State for each replica.
-
-Example:
-
-* Partition-1, replica-1, Master, Node-1
-* Partition-1, replica-2, Slave, Node-2
-* Partition-1, replica-3, Slave, Node-3
-* .....
-* .....
-* Partition-p, replica-3, Slave, Node-n
-
-Helix comes with various algorithms to automatically assign the partitions to nodes. The default algorithm minimizes the number of shuffles that happen when new nodes are added to the system.
-
-### CurrentState
-
-Every instance in the cluster hosts one or more partitions of a resource. Each of the partitions has a state associated with it.
-
-Example Node-1
-
-* Partition-1, Master
-* Partition-2, Slave
-* ....
-* ....
-* Partition-p, Slave
-
-### ExternalView
-
-External clients needs to know the state of each partition in the cluster and the Node hosting that partition. Helix provides one view of the system to Spectators as _ExternalView_. ExternalView is simply an aggregate of all node CurrentStates.
-
-* Partition-1, replica-1, Master, Node-1
-* Partition-1, replica-2, Slave, Node-2
-* Partition-1, replica-3, Slave, Node-3
-* .....
-* .....
-* Partition-p, replica-3, Slave, Node-n
-
-## Process Workflow
-
-Mode of operation in a cluster
-
-A node process can be one of the following:
-
-* Participant: The process registers itself in the cluster and acts on the messages received in its queue and updates the current state. Example: a storage node in a distributed database
-* Spectator: The process is simply interested in the changes in the Externalview.
-* Controller: This process actively controls the cluster by reacting to changes in cluster state and sending messages to Participants.
-
-
-### Participant Node Process
-
-* When Node starts up, it registers itself under _LiveInstances_
-* After registering, it waits for new _Messages_ in the message queue
-* When it receives a message, it will perform the required task as indicated in the message
-* After the task is completed, depending on the task outcome it updates the CurrentState
-
-### Controller Process
-
-* Watches IdealState
-* Notified when a node goes down/comes up or node is added/removed. Watches LiveInstances and CurrentState of each node in the cluster
-* Triggers appropriate state transitions by sending message to Participants
-
-### Spectator Process
-
-* When the process starts, it asks the Helix agent to be notified of changes in ExternalView
-* Whenever it receives a notification, it reads the Externalview and performs required duties.
-
-#### Interaction between controller, participant and spectator
-
-The following picture shows how controllers, participants and spectators interact with each other.
-
-
-
-## Core algorithm
-
-* Controller gets the IdealState and the CurrentState of active storage nodes from Zookeeper
-* Compute the delta between IdealState and CurrentState for each partition across all participant nodes
-* For each partition compute tasks based on the State Machine Table. It\'s possible to configure priority on the state Transition. For example, in case of Master-Slave:
- * Attempt mastership transfer if possible without violating constraint.
- * Partition Addition
- * Drop Partition
-* Add the tasks in parallel if possible to the respective queue for each storage node (if the tasks added are mutually independent)
-* If a task is dependent on another task being completed, do not add that task
-* After any task is completed by a Participant, Controllers gets notified of the change and the State Transition algorithm is re-run until the CurrentState is same as IdealState.
-
-## Helix ZNode layout
-
-Helix organizes znodes under clusterName in multiple levels.
-
-The top level (under the cluster name) ZNodes are all Helix-defined and in upper case:
-
-* PROPERTYSTORE: application property store
-* STATEMODELDEFES: state model definitions
-* INSTANCES: instance runtime information including current state and messages
-* CONFIGS: configurations
-* IDEALSTATES: ideal states
-* EXTERNALVIEW: external views
-* LIVEINSTANCES: live instances
-* CONTROLLER: cluster controller runtime information
-
-Under INSTANCES, there are runtime ZNodes for each instance. An instance organizes ZNodes as follows:
-
-* CURRENTSTATES
- * sessionId
- * resourceName
-* ERRORS
-* STATUSUPDATES
-* MESSAGES
-* HEALTHREPORT
-
-Under CONFIGS, there are different scopes of configurations:
-
-* RESOURCE: contains resource scope configurations
-* CLUSTER: contains cluster scope configurations
-* PARTICIPANT: contains participant scope configurations
-
-The following image shows an example of Helix znodes layout for a cluster named "test-cluster":
-
-
http://git-wip-us.apache.org/repos/asf/incubator-helix/blob/4a4510d1/site-releases/trunk/src/site/markdown/Building.md
----------------------------------------------------------------------
diff --git a/site-releases/trunk/src/site/markdown/Building.md b/site-releases/trunk/src/site/markdown/Building.md
index 2d8a51b..6ea8777 100644
--- a/site-releases/trunk/src/site/markdown/Building.md
+++ b/site-releases/trunk/src/site/markdown/Building.md
@@ -20,6 +20,8 @@ under the License.
Build Instructions
------------------
+### From Source
+
Requirements: JDK 1.6+, Maven 2.0.8+
```