Package org.apache.hadoop.ipc

Class RetryCache

java.lang.Object

org.apache.hadoop.ipc.RetryCache

@Private
public class RetryCache
extends Object

Maintains a cache of non-idempotent requests that have been successfully processed by the RPC server implementation, to handle the retries. A request is uniquely identified by the unique client ID + call ID of the RPC request. On receiving retried request, an entry will be found in the RetryCache and the previous response is sent back to the request.

To look an implementation using this cache, see HDFS FSNamesystem class.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	RetryCache.CacheEntry	CacheEntry is tracked using unique client ID and callId of the RPC request.
static class	RetryCache.CacheEntryWithPayload	CacheEntry with payload that tracks the previous response or parts of previous response to be used for generating response for retried requests.

Field Summary

Fields

Modifier and Type	Field	Description
static final org.slf4j.Logger	LOG

Constructor Summary

Constructors

Constructor	Description
RetryCache(String cacheName, double percentage, long expirationTime)	Constructor

Method Summary

Modifier and Type	Method	Description
void	addCacheEntry(byte[] clientId, int callId)	Add a new cache entry into the retry cache.
void	addCacheEntryWithPayload(byte[] clientId, int callId, Object payload)
static void	clear(RetryCache cache)
String	getCacheName()
LightWeightGSet<RetryCache.CacheEntry,RetryCache.CacheEntry>	getCacheSet()
RetryCacheMetrics	getMetricsForTests()
void	lock()
static void	setState(RetryCache.CacheEntry e, boolean success)
static void	setState(RetryCache.CacheEntryWithPayload e, boolean success, Object payload)
void	unlock()
static RetryCache.CacheEntry	waitForCompletion(RetryCache cache, byte[] clientId, int callId)	Static method that provides null check for retryCache.
static RetryCache.CacheEntryWithPayload	waitForCompletion(RetryCache cache, Object payload, byte[] clientId, int callId)	Static method that provides null check for retryCache.

Methods inherited from class java.lang.Object

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

Field Details

LOG

public static final org.slf4j.Logger LOG

Constructor Details

RetryCache

public RetryCache(String cacheName,
 double percentage,
 long expirationTime)

Constructor

Parameters:

cacheName - name to identify the cache by

percentage - percentage of total java heap space used by this cache

expirationTime - time for an entry to expire in nanoseconds

Method Details

lock

public void lock()

unlock

public void unlock()

getCacheSet

@VisibleForTesting
public LightWeightGSet<RetryCache.CacheEntry,RetryCache.CacheEntry> getCacheSet()

getMetricsForTests

@VisibleForTesting
public RetryCacheMetrics getMetricsForTests()

getCacheName

public String getCacheName()

Returns:

This method returns cache name for metrics.

addCacheEntry

public void addCacheEntry(byte[] clientId,
 int callId)

Add a new cache entry into the retry cache. The cache entry consists of clientId and callId extracted from editlog.

Parameters:

clientId - input clientId.

callId - input callId.

addCacheEntryWithPayload

public void addCacheEntryWithPayload(byte[] clientId,
 int callId,
 Object payload)

waitForCompletion

public static RetryCache.CacheEntry waitForCompletion(RetryCache cache,
 byte[] clientId,
 int callId)

Static method that provides null check for retryCache.

Parameters:

cache - input Cache.

clientId - client id of this request

callId - client call id of this request

Returns:

CacheEntry.

waitForCompletion

public static RetryCache.CacheEntryWithPayload waitForCompletion(RetryCache cache,
 Object payload,
 byte[] clientId,
 int callId)

Static method that provides null check for retryCache.

Parameters:

cache - input cache.

payload - input payload.

clientId - client id of this request

callId - client call id of this request

Returns:

CacheEntryWithPayload.

setState

public static void setState(RetryCache.CacheEntry e,
 boolean success)

setState

public static void setState(RetryCache.CacheEntryWithPayload e,
 boolean success,
 Object payload)

clear

public static void clear(RetryCache cache)