Package org.apache.hadoop.yarn.client.api

Class SharedCacheClient

java.lang.Object

org.apache.hadoop.service.AbstractService

org.apache.hadoop.yarn.client.api.SharedCacheClient

All Implemented Interfaces:

Closeable, AutoCloseable, Service

@Public
@Unstable
public abstract class SharedCacheClient
extends AbstractService

This is the client for YARN's shared cache.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.hadoop.service.Service

Service.STATE

Constructor Summary

Constructors

Constructor	Description
SharedCacheClient(String name)

Method Summary

Modifier and Type	Method	Description
static SharedCacheClient	createSharedCacheClient()
abstract String	getFileChecksum(Path sourceFile)	A convenience method to calculate the checksum of a specified file.
abstract void	release(ApplicationId applicationId, String resourceKey)	The method to release a resource with the SharedCacheManager. This method is called once an application is no longer using a claimed resource in the shared cache.
abstract URL	use(ApplicationId applicationId, String resourceKey)	The method to claim a resource with the SharedCacheManager. The client uses a checksum to identify the resource and an ApplicationId to identify which application will be using the resource.

Methods inherited from class org.apache.hadoop.service.AbstractService

close, getBlockers, getConfig, getFailureCause, getFailureState, getLifecycleHistory, getName, getServiceState, getStartTime, init, isInState, noteFailure, putBlocker, registerGlobalListener, registerServiceListener, removeBlocker, serviceInit, serviceStart, serviceStop, setConfig, start, stop, toString, unregisterGlobalListener, unregisterServiceListener, waitForServiceToStop

Methods inherited from class java.lang.Object

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

Constructor Details

SharedCacheClient

@Private
public SharedCacheClient(String name)

Method Details

createSharedCacheClient

@Public
public static SharedCacheClient createSharedCacheClient()

use

@Public
@Unstable
public abstract URL use(ApplicationId applicationId,
 String resourceKey)
                 throws YarnException

The method to claim a resource with the SharedCacheManager. The client uses a checksum to identify the resource and an ApplicationId to identify which application will be using the resource.

The SharedCacheManager responds with whether or not the resource exists in the cache. If the resource exists, a URL to the resource in the shared cache is returned. If the resource does not exist, null is returned instead.

Once a URL has been returned for a resource, that URL is safe to use for the lifetime of the application that corresponds to the provided ApplicationId.

Parameters:

applicationId - ApplicationId of the application using the resource

resourceKey - the key (i.e. checksum) that identifies the resource

Returns:

URL to the resource, or null if it does not exist

Throws:

YarnException

release

@Public
@Unstable
public abstract void release(ApplicationId applicationId,
 String resourceKey)
                      throws YarnException

The method to release a resource with the SharedCacheManager. This method is called once an application is no longer using a claimed resource in the shared cache. The client uses a checksum to identify the resource and an ApplicationId to identify which application is releasing the resource.

Note: This method is an optimization and the client is not required to call it for correctness.

Parameters:

applicationId - ApplicationId of the application releasing the resource

resourceKey - the key (i.e. checksum) that identifies the resource

Throws:

YarnException

getFileChecksum

@Public
@Unstable
public abstract String getFileChecksum(Path sourceFile)
                                throws IOException

A convenience method to calculate the checksum of a specified file.

Parameters:

sourceFile - A path to the input file

Returns:

A hex string containing the checksum digest

Throws:

IOException