org.apache.hadoop.tools.util
Class RetriableCommand

java.lang.Object
  org.apache.hadoop.tools.util.RetriableCommand

Direct Known Subclasses:

RetriableDirectoryCreateCommand, RetriableFileCopyCommand

public abstract class RetriableCommand
extends Object

This class represents commands that be retried on failure, in a configurable manner.

Field Summary

protected String

description

Constructor Summary

RetriableCommand(String description)
Constructor.

RetriableCommand(String description, RetryPolicy retryPolicy)
Constructor.

Method Summary

protected abstract Object	doExecute(Object... arguments) Implement this interface-method define the command-logic that will be retried on failure (i.e.
Object	execute(Object... arguments) The execute() method invokes doExecute() until either: 1.
RetriableCommand	setRetryPolicy(RetryPolicy retryHandler) Fluent-interface to change the RetryHandler.

Methods inherited from class java.lang.Object

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

Field Detail

description

protected String description

Constructor Detail

RetriableCommand

public RetriableCommand(String description)

Constructor.

Parameters:

description - The human-readable description of the command.

RetriableCommand

public RetriableCommand(String description,
                        RetryPolicy retryPolicy)

Constructor.

Parameters:

description - The human-readable description of the command.

retryPolicy - The RetryHandler to be used to compute retries.

Method Detail

doExecute

protected abstract Object doExecute(Object... arguments)
                             throws Exception

Implement this interface-method define the command-logic that will be retried on failure (i.e. with Exception).

Parameters:

arguments - Argument-list to the command.

Returns:

Generic "Object".

Throws:

Exception - Throws Exception on complete failure.

execute

public Object execute(Object... arguments)
               throws Exception

The execute() method invokes doExecute() until either: 1. doExecute() succeeds, or 2. the command may no longer be retried (e.g. runs out of retry-attempts).

Parameters:

arguments - The list of arguments for the command.

Returns:

Generic "Object" from doExecute(), on success.

Throws:

IOException, - IOException, on complete failure.

Exception

setRetryPolicy

public RetriableCommand setRetryPolicy(RetryPolicy retryHandler)

Fluent-interface to change the RetryHandler.

Parameters:

retryHandler - The new RetryHandler instance to be used.

Returns:

Self.