org.apache.twill.internal

Class AbstractTwillService

java.lang.Object

com.google.common.util.concurrent.AbstractExecutionThreadService

org.apache.twill.internal.AbstractTwillService

All Implemented Interfaces:

com.google.common.util.concurrent.Service, org.apache.twill.internal.state.MessageCallback

public abstract class AbstractTwillService
extends com.google.common.util.concurrent.AbstractExecutionThreadService
implements org.apache.twill.internal.state.MessageCallback

A base implementation of Service that uses ZooKeeper to transmit states and messages. It uses the following directory structure in ZK:

 /instances
     |- [runId_1]
     |- [runId_2]
     |- ...
 /[runId_1]
     |- messages
          |- [messageId_1]
          |- [messageId_2]
          |- ....
 /[runId_2]
     |- messages
 

It assumes that the zk root node is already namespaced (either with applicationId for AM or runnableId for containers).

The ephemeral nodes under /instances are the liveNode for each running instance. It can carries data about that service, which is set by the corresponding implementation.

Each running instance also has its own node named by the runId. Under that node, it has a messages node for receiving messages from the controller. New message is created by creating a sequence node under the messages node, with the node data carrying the message content. The message node will be removed once the message is being processed by the service.

Nested Class Summary

Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service

com.google.common.util.concurrent.Service.Listener, com.google.common.util.concurrent.Service.State

Field Summary

Fields

Modifier and Type	Field and Description
protected RunId	runId
protected ZKClient	zkClient

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractTwillService(ZKClient zkClient, RunId runId)

Method Summary

Modifier and Type	Method and Description
protected void	doRun() Override to execution service work.
protected void	doStart() Override to perform any work during service start.
protected void	doStop() Overrides to perform any work during service shutdown.
protected Object	getLiveNodeData() Returns an Object to be stored in the live node.
protected com.google.gson.Gson	getLiveNodeGson() Returns a Gson instance for serializing object returned by the getLiveNodeData() method.
com.google.common.util.concurrent.ListenableFuture<String>	onReceived(String messageId, org.apache.twill.internal.state.Message message) Handles message by simply logging it.
protected void	run()
protected void	shutDown()
protected void	startUp()
protected OperationFuture<?>	updateLiveNode() Update the live node for the service.

Methods inherited from class com.google.common.util.concurrent.AbstractExecutionThreadService

addListener, awaitRunning, awaitRunning, awaitTerminated, awaitTerminated, executor, failureCause, isRunning, serviceName, start, startAndWait, startAsync, state, stop, stopAndWait, stopAsync, toString, triggerShutdown

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

zkClient

protected final ZKClient zkClient

runId

protected final RunId runId

Constructor Detail

AbstractTwillService

protected AbstractTwillService(ZKClient zkClient,
                               RunId runId)

Method Detail

doStart

protected void doStart()
                throws Exception

Override to perform any work during service start.

Throws:

Exception

doRun

protected void doRun()
              throws Exception

Override to execution service work. When this method returns, this Service will stop.

Throws:

Exception

doStop

protected void doStop()
               throws Exception

Overrides to perform any work during service shutdown.

Throws:

Exception

getLiveNodeData

protected Object getLiveNodeData()

Returns an Object to be stored in the live node. The object return will be GSon serialized. If null is returned, no data will be stored to the live node.

getLiveNodeGson

protected com.google.gson.Gson getLiveNodeGson()

Returns a Gson instance for serializing object returned by the getLiveNodeData() method.

onReceived

public com.google.common.util.concurrent.ListenableFuture<String> onReceived(String messageId,
                                                                             org.apache.twill.internal.state.Message message)

Handles message by simply logging it. Child class should override this method for custom handling of message.

Specified by:

onReceived in interface org.apache.twill.internal.state.MessageCallback

message - Message being received.

Returns:

A ListenableFuture that would be completed when message processing is completed or failed. The result of the future should be the input message Id if succeeded.

See Also:

MessageCallback

startUp

protected final void startUp()
                      throws Exception

Overrides:

startUp in class com.google.common.util.concurrent.AbstractExecutionThreadService

Throws:

Exception

run

protected final void run()
                  throws Exception

Specified by:

run in class com.google.common.util.concurrent.AbstractExecutionThreadService

Throws:

Exception

shutDown

protected final void shutDown()
                       throws Exception

Overrides:

shutDown in class com.google.common.util.concurrent.AbstractExecutionThreadService

Throws:

Exception

updateLiveNode

protected final OperationFuture<?> updateLiveNode()

Update the live node for the service.

Returns:

A OperationFuture that will be completed when the update is done.