org.apache.hadoop.yarn.applications.distributedshell

Class ApplicationMaster

java.lang.Object

org.apache.hadoop.yarn.applications.distributedshell.ApplicationMaster

@InterfaceAudience.Public
@InterfaceStability.Unstable
public class ApplicationMaster
extends Object

An ApplicationMaster for executing shell commands on a set of launched containers using the YARN framework.

This class is meant to act as an example on how to write yarn-based application masters.

The ApplicationMaster is started on a container by the ResourceManager's launcher. The first thing that the ApplicationMaster needs to do is to connect and register itself with the ResourceManager. The registration sets up information within the ResourceManager regarding what host:port the ApplicationMaster is listening on to provide any form of functionality to a client as well as a tracking url that a client can use to keep track of status/job history if needed. However, in the distributedshell, trackingurl and appMasterHost:appMasterRpcPort are not supported.

The ApplicationMaster needs to send a heartbeat to the ResourceManager at regular intervals to inform the ResourceManager that it is up and alive. The ApplicationMasterProtocol.allocate(org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest) to the ResourceManager from the ApplicationMaster acts as a heartbeat.

For the actual handling of the job, the ApplicationMaster has to request the ResourceManager via AllocateRequest for the required no. of containers using ResourceRequest with the necessary resource specifications such as node location, computational (memory/disk/cpu) resource requirements. The ResourceManager responds with an AllocateResponse that informs the ApplicationMaster of the set of newly allocated containers, completed containers as well as current state of available resources.

For each allocated container, the ApplicationMaster can then set up the necessary launch context via ContainerLaunchContext to specify the allocated container id, local resources required by the executable, the environment to be setup for the executable, commands to execute, etc. and submit a StartContainerRequest to the ContainerManagementProtocol to launch and execute the defined commands on the given allocated container.

The ApplicationMaster can monitor the launched container by either querying the ResourceManager using ApplicationMasterProtocol.allocate(org.apache.hadoop.yarn.api.protocolrecords.AllocateRequest) to get updates on completed containers or via the ContainerManagementProtocol by querying for the status of the allocated container's ContainerId.

After the job has been completed, the ApplicationMaster has to send a FinishApplicationMasterRequest to the ResourceManager to inform it that the ApplicationMaster has been completed.

Field Summary

Fields

Modifier and Type	Field and Description
protected ApplicationAttemptId	appAttemptID
protected Set<ContainerId>	launchedContainers
protected AtomicInteger	numAllocatedContainers
protected AtomicInteger	numRequestedContainers
protected int	numTotalContainers

Constructor Summary

Constructors

Constructor and Description
ApplicationMaster()

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	finish()
boolean	init(String[] args) Parse command line options
static void	main(String[] args)
void	run() Main run function for the application master

Methods inherited from class java.lang.Object

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

Field Detail

appAttemptID

protected ApplicationAttemptId appAttemptID

numTotalContainers

protected int numTotalContainers

numAllocatedContainers

protected AtomicInteger numAllocatedContainers

numRequestedContainers

protected AtomicInteger numRequestedContainers

launchedContainers

protected final Set<ContainerId> launchedContainers

Constructor Detail

ApplicationMaster

public ApplicationMaster()

Method Detail

main

public static void main(String[] args)

Parameters:

args - Command line args

init

public boolean init(String[] args)
             throws org.apache.commons.cli.ParseException,
                    IOException

Parse command line options

Parameters:

args - Command line args

Returns:

Whether init successful and run should be invoked

Throws:

org.apache.commons.cli.ParseException

IOException

run

public void run()
         throws YarnException,
                IOException,
                InterruptedException

Main run function for the application master

Throws:

YarnException

IOException

InterruptedException

finish

protected boolean finish()