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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.curator;
import com.yahoo.concurrent.UncheckedTimeoutException;
import com.yahoo.path.Path;
import com.yahoo.transaction.Mutex;
import com.yahoo.vespa.curator.stats.LockStats;
import com.yahoo.vespa.curator.stats.ThreadLockStats;
import org.apache.curator.framework.recipes.locks.InterProcessLock;
import java.time.Duration;
import java.time.Instant;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;
/**
* A cluster-wide re-entrant mutex which is released on (the last symmetric) close.
*
* Re-entrancy is limited to the instance of this. To ensure re-entrancy callers should access the lock through
* {@link Curator#lock(Path, Duration)} instead of constructing this directly.
*
* @author bratseth
*/
public class Lock implements Mutex {
// TODO(hakon): Remove once debugging is done
private final Object monitor = new Object();
private long nextSequenceNumber = 0;
private final Map<Long, Long> reentriesByThreadId = new HashMap<>();
private final Instant created = Instant.now();
private Curator curator;
private final InterProcessLock mutex;
private final String lockPath;
public Lock(String lockPath, Curator curator) {
this(lockPath, curator.createMutex(lockPath));
this.curator = curator;
}
/** Public for testing only */
public Lock(String lockPath, InterProcessLock mutex) {
this.lockPath = lockPath;
this.mutex = mutex;
this.curator = null;
}
/** Take the lock with the given timeout. This may be called multiple times from the same thread - each matched by a close */
public void acquire(Duration timeout) throws UncheckedTimeoutException {
ThreadLockStats threadLockStats = LockStats.getForCurrentThread();
threadLockStats.invokingAcquire(lockPath, timeout);
final boolean acquired;
try {
acquired = mutex.acquire(timeout.toMillis(), TimeUnit.MILLISECONDS);
} catch (Exception e) {
threadLockStats.acquireFailed();
throw new RuntimeException("Exception acquiring lock '" + lockPath + "'", e);
}
if (!acquired) {
threadLockStats.acquireTimedOut();
throw new UncheckedTimeoutException("Timed out after waiting " + timeout +
" to acquire lock '" + lockPath + "'");
}
invoke(+1L, (lockPath, debug) -> threadLockStats.lockAcquired(debug), lockPath);
}
@FunctionalInterface
private interface BiConsumer2 {
void accept(String lockPath, String debug);
}
// TODO(hakon): Remove once debugging is unnecessary
private void invoke(long reentryCountDiff, BiConsumer2 consumer, String lockPath) {
long threadId = Thread.currentThread().getId();
final long sequenceNumber;
final Map<Long, Long> reentriesByThreadIdCopy;
synchronized (monitor) {
sequenceNumber = nextSequenceNumber++;
reentriesByThreadId.merge(threadId, reentryCountDiff, (oldValue, argumentValue) -> {
long sum = oldValue + argumentValue /* == reentryCountDiff */;
if (sum == 0) {
// Remove from map
return null;
} else {
return sum;
}
});
reentriesByThreadIdCopy = Map.copyOf(reentriesByThreadId);
}
String debug = "thread " + threadId + " Lock 0x" + Integer.toHexString(System.identityHashCode(this)) +
"@" + created + " Curator 0x" + Integer.toHexString(System.identityHashCode(curator)) +
" lock " + lockPath + " #" + sequenceNumber +
", reentries by thread ID = " + reentriesByThreadIdCopy;
consumer.accept(lockPath, debug);
}
@Override
public void close() {
ThreadLockStats threadLockStats = LockStats.getForCurrentThread();
// Update metrics now before release() to avoid double-counting time in locked state.
// The lockPath must be sent down as close() may be invoked in an order not necessarily
// equal to the reverse order of acquires.
invoke(-1L, threadLockStats::preRelease, lockPath);
try {
mutex.release();
threadLockStats.postRelease(lockPath);
}
catch (Exception e) {
threadLockStats.releaseFailed(lockPath);
throw new RuntimeException("Exception releasing lock '" + lockPath + "'", e);
}
}
protected String lockPath() { return lockPath; }
@Override
public String toString() {
return "Lock{" + lockPath + "}";
}
}
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