org.apache.hadoop.hbase.regionserver.wal

Class FSHLog.SyncRunner

java.lang.Object

org.apache.hadoop.hbase.util.HasThread

org.apache.hadoop.hbase.regionserver.wal.FSHLog.SyncRunner

All Implemented Interfaces:

Runnable

Enclosing class:

FSHLog

private class FSHLog.SyncRunner
extends HasThread

Thread to runs the hdfs sync call. This call takes a while to complete. This is the longest pole adding edits to the WAL and this must complete to be sure all edits persisted. We run multiple threads sync'ng rather than one that just syncs in series so we have better latencies; otherwise, an edit that arrived just after a sync started, might have to wait almost the length of two sync invocations before it is marked done.

When the sync completes, it marks all the passed in futures done. On the other end of the sync future is a blocked thread, usually a regionserver Handler. There may be more than one future passed in the case where a few threads arrive at about the same time and all invoke 'sync'. In this case we'll batch up the invocations and run one filesystem sync only for a batch of Handler sync invocations. Do not confuse these Handler SyncFutures with the futures an ExecutorService returns when you call submit. We have no use for these in this model. These SyncFutures are 'artificial', something to hold the Handler until the filesystem sync completes.

Field Summary

Fields

Modifier and Type	Field and Description
private long	sequence
private BlockingQueue<SyncFuture>	syncFutures
private SyncFuture	takeSyncFuture

Constructor Summary

Constructors

Constructor and Description
SyncRunner(String name, int maxHandlersCount)

Method Summary

Modifier and Type	Method and Description
(package private) boolean	areSyncFuturesReleased()
(package private) void	offer(long sequence, SyncFuture[] syncFutures, int syncFutureCount)
private int	releaseSyncFuture(SyncFuture syncFuture, long currentSequence, Throwable t) Release the passed syncFuture
private int	releaseSyncFutures(long currentSequence, Throwable t) Release all SyncFutures whose sequence is <= currentSequence.
void	run()
private long	updateHighestSyncedSequence(long sequence)

Methods inherited from class org.apache.hadoop.hbase.util.HasThread

getName, getThread, interrupt, isAlive, isInterrupted, join, join, join, setDaemon, setName, setPriority, setUncaughtExceptionHandler, start

Methods inherited from class java.lang.Object

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

Field Detail

sequence

private volatile long sequence

syncFutures

private final BlockingQueue<SyncFuture> syncFutures

takeSyncFuture

private volatile SyncFuture takeSyncFuture

Constructor Detail

SyncRunner

SyncRunner(String name,
           int maxHandlersCount)

Method Detail

offer

void offer(long sequence,
           SyncFuture[] syncFutures,
           int syncFutureCount)

releaseSyncFuture

private int releaseSyncFuture(SyncFuture syncFuture,
                              long currentSequence,
                              Throwable t)

Release the passed syncFuture

Returns:

Returns 1.

releaseSyncFutures

private int releaseSyncFutures(long currentSequence,
                               Throwable t)

Release all SyncFutures whose sequence is <= currentSequence.

Parameters:

t - May be non-null if we are processing SyncFutures because an exception was thrown.

Returns:

Count of SyncFutures we let go.

updateHighestSyncedSequence

private long updateHighestSyncedSequence(long sequence)

Parameters:

sequence - The sequence we ran the filesystem sync against.

Returns:

Current highest synced sequence.

areSyncFuturesReleased

boolean areSyncFuturesReleased()

run

public void run()

Specified by:

run in interface Runnable

Specified by:

run in class HasThread