/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.db.commitlog;
import org.apache.cassandra.utils.concurrent.WaitQueue;
import org.slf4j.*;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import static org.apache.cassandra.db.commitlog.CommitLogSegment.Allocation;
public abstract class AbstractCommitLogService
{
// how often should we log syngs that lag behind our desired period
private static final long LAG_REPORT_INTERVAL = TimeUnit.MINUTES.toMillis(5);
private final Thread thread;
private volatile boolean shutdown = false;
// all Allocations written before this time will be synced
protected volatile long lastSyncedAt = System.currentTimeMillis();
// counts of total written, and pending, log messages
private final AtomicLong written = new AtomicLong(0);
protected final AtomicLong pending = new AtomicLong(0);
// signal that writers can wait on to be notified of a completed sync
protected final WaitQueue syncComplete = new WaitQueue();
private final Semaphore haveWork = new Semaphore(1);
private static final Logger logger = LoggerFactory.getLogger(AbstractCommitLogService.class);
/**
* CommitLogService provides a fsync service for Allocations, fulfilling either the
* Batch or Periodic contract.
*
* Subclasses may be notified when a sync finishes by using the syncComplete WaitQueue.
*/
AbstractCommitLogService(final CommitLog commitLog, final String name, final long pollIntervalMillis)
{
if (pollIntervalMillis < 1)
throw new IllegalArgumentException(String.format("Commit log flush interval must be positive: %dms", pollIntervalMillis));
Runnable runnable = new Runnable()
{
public void run()
{
long firstLagAt = 0;
long totalSyncDuration = 0; // total time spent syncing since firstLagAt
long syncExceededIntervalBy = 0; // time that syncs exceeded pollInterval since firstLagAt
int lagCount = 0;
int syncCount = 0;
boolean run = true;
while (run)
{
try
{
// always run once after shutdown signalled
run = !shutdown;
// sync and signal
long syncStarted = System.currentTimeMillis();
commitLog.sync(shutdown);
lastSyncedAt = syncStarted;
syncComplete.signalAll();
// sleep any time we have left before the next one is due
long now = System.currentTimeMillis();
long sleep = syncStarted + pollIntervalMillis - now;
if (sleep < 0)
{
// if we have lagged noticeably, update our lag counter
if (firstLagAt == 0)
{
firstLagAt = now;
totalSyncDuration = syncExceededIntervalBy = syncCount = lagCount = 0;
}
syncExceededIntervalBy -= sleep;
lagCount++;
}
syncCount++;
totalSyncDuration += now - syncStarted;
if (firstLagAt > 0 && now - firstLagAt >= LAG_REPORT_INTERVAL)
{
logger.warn(String.format("Out of %d commit log syncs over the past %ds with average duration of %.2fms, %d have exceeded the configured commit interval by an average of %.2fms",
syncCount, (now - firstLagAt) / 1000, (double) totalSyncDuration / syncCount, lagCount, (double) syncExceededIntervalBy / lagCount));
firstLagAt = 0;
}
// if we have lagged this round, we probably have work to do already so we don't sleep
if (sleep < 0 || !run)
continue;
try
{
haveWork.tryAcquire(sleep, TimeUnit.MILLISECONDS);
}
catch (InterruptedException e)
{
throw new AssertionError();
}
}
catch (Throwable t)
{
if (!CommitLog.handleCommitError("Failed to persist commits to disk", t))
break;
// sleep for full poll-interval after an error, so we don't spam the log file
try
{
haveWork.tryAcquire(pollIntervalMillis, TimeUnit.MILLISECONDS);
}
catch (InterruptedException e)
{
throw new AssertionError();
}
}
}
}
};
thread = new Thread(runnable, name);
thread.start();
}
/**
* Block for @param alloc to be sync'd as necessary, and handle bookkeeping
*/
public void finishWriteFor(Allocation alloc)
{
maybeWaitForSync(alloc);
written.incrementAndGet();
}
protected abstract void maybeWaitForSync(Allocation alloc);
/**
* Sync immediately, but don't block for the sync to cmplete
*/
public WaitQueue.Signal requestExtraSync()
{
WaitQueue.Signal signal = syncComplete.register();
haveWork.release(1);
return signal;
}
public void shutdown()
{
shutdown = true;
haveWork.release(1);
}
public void awaitTermination() throws InterruptedException
{
thread.join();
}
public long getCompletedTasks()
{
return written.incrementAndGet();
}
public long getPendingTasks()
{
return pending.get();
}
}