alluxio.client.file.dora

Class ConsistentHashPolicy

java.lang.Object

alluxio.client.file.dora.ConsistentHashPolicy

All Implemented Interfaces:

WorkerLocationPolicy

public class ConsistentHashPolicy
extends Object
implements WorkerLocationPolicy

An impl of WorkerLocationPolicy. A policy where a file path is matched to worker(s) by a consistenct hashing algorithm. The hash algorithm makes sure the same path maps to the same worker sequence. On top of that, consistent hashing makes sure worker membership changes incur minimal hash changes.

Nested Class Summary

Nested classes/interfaces inherited from interface alluxio.client.file.dora.WorkerLocationPolicy

WorkerLocationPolicy.Factory

Constructor Summary

Constructors

Constructor and Description
ConsistentHashPolicy(AlluxioConfiguration conf) Constructs a new ConsistentHashPolicy.

Method Summary

Modifier and Type	Method and Description
List<BlockWorkerInfo>	getPreferredWorkers(List<BlockWorkerInfo> blockWorkerInfos, String fileId, int count) Find a specified number of workers following the logic defined by the policy.

Methods inherited from class java.lang.Object

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

Constructor Detail

ConsistentHashPolicy

public ConsistentHashPolicy(AlluxioConfiguration conf)

Constructs a new ConsistentHashPolicy.

Parameters:

conf - the configuration used by the policy

Method Detail

getPreferredWorkers

public List<BlockWorkerInfo> getPreferredWorkers(List<BlockWorkerInfo> blockWorkerInfos,
                                                 String fileId,
                                                 int count)
                                          throws ResourceExhaustedException

Description copied from interface: WorkerLocationPolicy

Find a specified number of workers following the logic defined by the policy. This method should return exactly #{count} different workers, no more no less. If the specified number of workers cannot be found, this method will throw a ResourceExhaustedException. We want the semantics here to be explicit when the requirement cannot be satisfied. So the caller should define its own logic handling the exception and finding backups.

Specified by:

getPreferredWorkers in interface WorkerLocationPolicy

Returns:

a list of preferred workers

Throws:

ResourceExhaustedException - if unable to return exactly #{count} workers