com.google.appengine.tools.mapreduce.impl.handlers

Class MemoryLimiter

java.lang.Object

com.google.appengine.tools.mapreduce.impl.handlers.MemoryLimiter

public final class MemoryLimiter
extends Object

Limits the number of parallel requests according to their estimated memory usage. Estimates are specified in MB. For internal use only. User code cannot safely depend on this class.

Field Summary

Fields

Modifier and Type	Field and Description
static int	TOTAL_CLAIMABLE_MEMORY_SIZE_MB

Constructor Summary

Constructors

Constructor and Description
MemoryLimiter()

Method Summary

Methods

Modifier and Type	Method and Description
long	claim(long toClaimMb) This method attempts to claim ram to the provided request.
void	release(long ammountUsed)

Methods inherited from class java.lang.Object

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

Field Detail

TOTAL_CLAIMABLE_MEMORY_SIZE_MB

public static final int TOTAL_CLAIMABLE_MEMORY_SIZE_MB

Constructor Detail

MemoryLimiter

public MemoryLimiter()

Method Detail

claim

public long claim(long toClaimMb)
           throws RejectRequestException

This method attempts to claim ram to the provided request. This may block waiting for some to be available. Ultimately it is either granted memory or an exception is thrown.

Parameters:

toClaimMb - The amount of memory the request wishes to claim. (In Megabytes)

Returns:

The amount of memory which was claimed. (This may be different from the amount requested.) This value needs to be passed to release(long) when the request exits.

Throws:

RejectRequestException - If the request should be rejected because it could not be given the resources requested.

release

public void release(long ammountUsed)

Parameters:

ammountUsed - the number returned from claim(long) when the request began. (Note that this is NOT the value that was passed to claim.)