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Elasticsearch subproject :server
/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
package org.elasticsearch.common.util.concurrent;
import org.elasticsearch.Assertions;
import org.elasticsearch.common.lease.Releasable;
import org.elasticsearch.common.unit.TimeValue;
import org.elasticsearch.index.engine.EngineException;
import java.util.concurrent.locks.Lock;
/**
* Releasable lock used inside of Engine implementations
*/
public class ReleasableLock implements Releasable {
private final Lock lock;
// a per-thread count indicating how many times the thread has entered the lock; only works if assertions are enabled
private final ThreadLocal holdingThreads;
public ReleasableLock(Lock lock) {
this.lock = lock;
if (Assertions.ENABLED) {
holdingThreads = new ThreadLocal<>();
} else {
holdingThreads = null;
}
}
@Override
public void close() {
lock.unlock();
assert removeCurrentThread();
}
public ReleasableLock acquire() throws EngineException {
lock.lock();
assert addCurrentThread();
return this;
}
/**
* Try acquiring lock, returning null if unable.
*/
public ReleasableLock tryAcquire() {
boolean locked = lock.tryLock();
if (locked) {
assert addCurrentThread();
return this;
} else {
return null;
}
}
/**
* Try acquiring lock, returning null if unable to acquire lock within timeout.
*/
public ReleasableLock tryAcquire(TimeValue timeout) throws InterruptedException {
boolean locked = lock.tryLock(timeout.duration(), timeout.timeUnit());
if (locked) {
assert addCurrentThread();
return this;
} else {
return null;
}
}
private boolean addCurrentThread() {
final Integer current = holdingThreads.get();
holdingThreads.set(current == null ? 1 : current + 1);
return true;
}
private boolean removeCurrentThread() {
final Integer count = holdingThreads.get();
assert count != null && count > 0;
if (count == 1) {
holdingThreads.remove();
} else {
holdingThreads.set(count - 1);
}
return true;
}
public boolean isHeldByCurrentThread() {
if (holdingThreads == null) {
throw new UnsupportedOperationException("asserts must be enabled");
}
final Integer count = holdingThreads.get();
return count != null && count > 0;
}
}