Package org.apache.hadoop.hdfs.server.federation.resolver

Class MultipleDestinationMountTableResolver

java.lang.Object

org.apache.hadoop.hdfs.server.federation.resolver.MountTableResolver

org.apache.hadoop.hdfs.server.federation.resolver.MultipleDestinationMountTableResolver

All Implemented Interfaces:

FileSubclusterResolver, StateStoreCache

public class MultipleDestinationMountTableResolver
extends MountTableResolver

Mount table resolver that supports multiple locations for each mount entry. The returned location contains prioritized remote paths from highest priority to the lowest priority. Multiple locations for a mount point are optional. When multiple locations are specified, both will be checked for the presence of a file and the nameservice for a new file/dir is chosen based on the results of a consistent hashing algorithm.

Does the Mount table entry for this path have multiple destinations?

• No: Return the location
• Yes: Return all locations, prioritizing the best guess from the consistent hashing algorithm.

It has multiple options to order the locations: HASH (default), LOCAL, RANDOM, and HASH_ALL.

The consistent hashing result is dependent on the number and combination of nameservices that are registered for particular mount point. The order of nameservices/locations in the mount table is not prioritized. Each consistent hash calculation considers only the set of unique nameservices present for the mount table location.

Constructor Summary

Constructors

Constructor	Description
MultipleDestinationMountTableResolver(org.apache.hadoop.conf.Configuration conf, Router router)

Method Summary

Modifier and Type	Method	Description
void	addResolver(DestinationOrder order, OrderedResolver resolver)
PathLocation	getDestinationForPath(String path)	Get the destinations for a global path.
OrderedResolver	getOrderedResolver(DestinationOrder order)

Methods inherited from class org.apache.hadoop.hdfs.server.federation.resolver.MountTableResolver

addEntry, clear, getCacheSize, getDefaultNameService, getDefaultNamespace, getLocCacheAccess, getLocCacheMiss, getMountPoint, getMountPoints, getMounts, getMountTableStore, getRouter, getTrashRoot, isDefaultNSEnable, isTrashPath, loadCache, lookupLocation, refreshEntries, removeEntry, setDefaultNameService, setDefaultNSEnable, setDisabled, subtractTrashCurrentPath, toString

Methods inherited from class java.lang.Object

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

Constructor Details

MultipleDestinationMountTableResolver

public MultipleDestinationMountTableResolver(org.apache.hadoop.conf.Configuration conf,
 Router router)

Method Details

getDestinationForPath

public PathLocation getDestinationForPath(String path)
                                   throws IOException

Description copied from interface: FileSubclusterResolver

Get the destinations for a global path. Results are from the mount table cache. If multiple destinations are available, the first result is the highest priority destination.

Specified by:

getDestinationForPath in interface FileSubclusterResolver

Overrides:

getDestinationForPath in class MountTableResolver

Parameters:

path - Global path.

Returns:

Location in a destination namespace or null if it does not exist.

Throws:

IOException - Throws exception if the data is not available.

addResolver

@VisibleForTesting
public void addResolver(DestinationOrder order,
 OrderedResolver resolver)

getOrderedResolver

@VisibleForTesting
public OrderedResolver getOrderedResolver(DestinationOrder order)