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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.config.server.filedistribution;
import com.yahoo.vespa.config.server.TimeoutBudget;
import com.yahoo.vespa.curator.Curator;
import com.yahoo.vespa.curator.recipes.CuratorLock;
import com.yahoo.vespa.curator.recipes.CuratorLockException;
import java.time.Clock;
import java.time.Duration;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
/**
* Global filedistribution lock to ensure only one configserver may work on filedistribution.
* The implementation uses a combination of a {@link java.util.concurrent.locks.ReentrantLock} and
* a {@link CuratorLock} to ensure both mutual exclusion within the JVM and
* across JVMs via ZooKeeper.
*
* @author lulf
*/
public class FileDistributionLock implements Lock {
private final Lock processLock;
private final CuratorLock curatorLock;
public FileDistributionLock(Curator curator, String zkPath) {
this.processLock = new ReentrantLock();
this.curatorLock = new CuratorLock(curator, zkPath);
}
@Override
public void lock() {
processLock.lock();
try {
curatorLock.lock();
} catch (CuratorLockException e) {
processLock.unlock();
throw e;
}
}
@Override
public void lockInterruptibly() throws InterruptedException {
throw new UnsupportedOperationException();
}
@Override
public boolean tryLock() {
if (processLock.tryLock()) {
if (curatorLock.tryLock()) {
return true;
} else {
processLock.unlock();
return false;
}
} else {
return false;
}
}
@Override
public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {
TimeoutBudget budget = new TimeoutBudget(Clock.systemUTC(), Duration.ofMillis(unit.toMillis(timeout)));
if (processLock.tryLock(budget.timeLeft().toMillis(), TimeUnit.MILLISECONDS)) {
if (curatorLock.tryLock(budget.timeLeft().toMillis(), TimeUnit.MILLISECONDS)) {
return true;
} else {
processLock.unlock();
return false;
}
} else {
return false;
}
}
@Override
public void unlock() {
try {
curatorLock.unlock();
} finally {
processLock.unlock();
}
}
@Override
public Condition newCondition() {
throw new UnsupportedOperationException();
}
}
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