com.zaxxer.hikari.util.SuspendResumeLock Maven / Gradle / Ivy
/*
* Copyright (C) 2013, 2014 Brett Wooldridge
*
* Licensed 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 com.zaxxer.hikari.util;
import java.sql.SQLException;
import java.sql.SQLTransientException;
import java.util.concurrent.Semaphore;
/**
* This class implements a lock that can be used to suspend and resume the pool. It
* also provides a faux implementation that is used when the feature is disabled that
* hopefully gets fully "optimized away" by the JIT.
*
* @author Brett Wooldridge
*/
public class SuspendResumeLock
{
public static final SuspendResumeLock FAUX_LOCK = new SuspendResumeLock(false) {
@Override
public void acquire() {}
@Override
public void release() {}
@Override
public void suspend() {}
@Override
public void resume() {}
};
private static final int MAX_PERMITS = 10000;
private final Semaphore acquisitionSemaphore;
/**
* Default constructor
*/
public SuspendResumeLock()
{
this(true);
}
private SuspendResumeLock(final boolean createSemaphore)
{
acquisitionSemaphore = (createSemaphore ? new Semaphore(MAX_PERMITS, true) : null);
}
public void acquire() throws SQLException
{
if (acquisitionSemaphore.tryAcquire()) {
return;
}
else if (Boolean.getBoolean("com.zaxxer.hikari.throwIfSuspended")) {
throw new SQLTransientException("The pool is currently suspended and configured to throw exceptions upon acquisition");
}
acquisitionSemaphore.acquireUninterruptibly();
}
public void release()
{
acquisitionSemaphore.release();
}
public void suspend()
{
acquisitionSemaphore.acquireUninterruptibly(MAX_PERMITS);
}
public void resume()
{
acquisitionSemaphore.release(MAX_PERMITS);
}
}