Package org.apache.hadoop.hdfs.server.namenode.ha

Class ObserverReadProxyProvider<T>

java.lang.Object

org.apache.hadoop.hdfs.server.namenode.ha.AbstractNNFailoverProxyProvider<T>

org.apache.hadoop.hdfs.server.namenode.ha.ObserverReadProxyProvider<T>

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.hadoop.io.retry.FailoverProxyProvider<T>

Direct Known Subclasses:

ObserverReadProxyProviderWithIPFailover

@Private
@Evolving
public class ObserverReadProxyProvider<T>
extends AbstractNNFailoverProxyProvider<T>

A FailoverProxyProvider implementation that supports reading from observer namenode(s). This constructs a wrapper proxy that sends the request to observer namenode(s), if observer read is enabled. In case there are multiple observer namenodes, it will try them one by one in case the RPC failed. It will fail back to the active namenode after it has exhausted all the observer namenodes. Read and write requests will still be sent to active NN if reading from observer is turned off.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.hadoop.hdfs.server.namenode.ha.AbstractNNFailoverProxyProvider

AbstractNNFailoverProxyProvider.NNProxyInfo<T>

Nested classes/interfaces inherited from interface org.apache.hadoop.io.retry.FailoverProxyProvider

org.apache.hadoop.io.retry.FailoverProxyProvider.ProxyInfo<T extends Object>

Field Summary

Fields inherited from class org.apache.hadoop.hdfs.server.namenode.ha.AbstractNNFailoverProxyProvider

conf, factory, fallbackToSimpleAuth, ugi, xface

Constructor Summary

Constructors

Constructor	Description
ObserverReadProxyProvider(org.apache.hadoop.conf.Configuration conf, URI uri, Class<T> xface, HAProxyFactory<T> factory)	By default ObserverReadProxyProvider uses ConfiguredFailoverProxyProvider for failover.
ObserverReadProxyProvider(org.apache.hadoop.conf.Configuration conf, URI uri, Class<T> xface, HAProxyFactory<T> factory, AbstractNNFailoverProxyProvider<T> failoverProxy)

Method Summary

Modifier and Type	Method	Description
void	close()
org.apache.hadoop.ipc.AlignmentContext	getAlignmentContext()
org.apache.hadoop.io.retry.FailoverProxyProvider.ProxyInfo<T>	getProxy()
void	performFailover(T currentProxy)
boolean	useLogicalURI()	Inquire whether logical HA URI is used for the implementation.

Methods inherited from class org.apache.hadoop.hdfs.server.namenode.ha.AbstractNNFailoverProxyProvider

createProxyIfNeeded, getFallbackToSimpleAuth, getInterface, getProxyAddresses, getRandomOrder, setFallbackToSimpleAuth

Methods inherited from class java.lang.Object

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

Constructor Details

ObserverReadProxyProvider

public ObserverReadProxyProvider(org.apache.hadoop.conf.Configuration conf,
 URI uri,
 Class<T> xface,
 HAProxyFactory<T> factory)

By default ObserverReadProxyProvider uses ConfiguredFailoverProxyProvider for failover.

ObserverReadProxyProvider

public ObserverReadProxyProvider(org.apache.hadoop.conf.Configuration conf,
 URI uri,
 Class<T> xface,
 HAProxyFactory<T> factory,
 AbstractNNFailoverProxyProvider<T> failoverProxy)

Method Details

getAlignmentContext

public org.apache.hadoop.ipc.AlignmentContext getAlignmentContext()

getProxy

public org.apache.hadoop.io.retry.FailoverProxyProvider.ProxyInfo<T> getProxy()

performFailover

public void performFailover(T currentProxy)

close

public void close()
           throws IOException

Throws:

IOException

useLogicalURI

public boolean useLogicalURI()

Description copied from class: AbstractNNFailoverProxyProvider

Inquire whether logical HA URI is used for the implementation. If it is used, a special token handling may be needed to make sure a token acquired from a node in the HA pair can be used against the other node.

Specified by:

useLogicalURI in class AbstractNNFailoverProxyProvider<T>

Returns:

true if logical HA URI is used. false, if not used.