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// Copyright Verizon Media. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.vespa.curator.stats;
import com.yahoo.vespa.curator.Lock;
import java.time.Duration;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.PriorityQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.function.Consumer;
/**
* This class contains process-wide statistics and information related to acquiring and releasing
* {@link Lock}. Instances of this class contain information tied to a specific thread and lock path.
*
* <p>Instances of this class are thread-safe as long as foreign threads (!= this.thread) avoid mutable methods.</p>
*
* @author hakon
*/
public class ThreadLockInfo {
private static final ConcurrentHashMap<Thread, ThreadLockInfo> locks = new ConcurrentHashMap<>();
private static final int MAX_COMPLETED_LOCK_INFOS_SIZE = 5;
/** Would have used a thread-safe priority queue. */
private static final Object completedLockInfosMonitor = new Object();
private static final PriorityQueue<LockInfo> completedLockInfos =
new PriorityQueue<>(Comparator.comparing(LockInfo::getDurationInTerminalStateAndForPriorityQueue));
private static final ConcurrentHashMap<String, LockCounters> countersByLockPath = new ConcurrentHashMap<>();
private final Thread thread;
private final String lockPath;
private final LockCounters lockCountersForPath;
/** The locks are reentrant so there may be more than 1 lock for this thread. */
private final ConcurrentLinkedQueue<LockInfo> lockInfos = new ConcurrentLinkedQueue<>();
public static Map<String, LockCounters> getLockCountersByPath() { return Map.copyOf(countersByLockPath); }
public static List<ThreadLockInfo> getThreadLockInfos() { return List.copyOf(locks.values()); }
public static List<LockInfo> getSlowLockInfos() {
synchronized (completedLockInfosMonitor) {
return List.copyOf(completedLockInfos);
}
}
/** Returns the per-thread singleton ThreadLockInfo. */
public static ThreadLockInfo getCurrentThreadLockInfo(String lockPath) {
return locks.computeIfAbsent(
Thread.currentThread(),
currentThread -> {
LockCounters lockCounters = countersByLockPath.computeIfAbsent(lockPath, ignored -> new LockCounters());
return new ThreadLockInfo(currentThread, lockPath, lockCounters);
});
}
static void clearStaticDataForTesting() {
locks.clear();
completedLockInfos.clear();
countersByLockPath.clear();
}
ThreadLockInfo(Thread currentThread, String lockPath, LockCounters lockCountersForPath) {
this.thread = currentThread;
this.lockPath = lockPath;
this.lockCountersForPath = lockCountersForPath;
}
public String getThreadName() { return thread.getName(); }
public String getLockPath() { return lockPath; }
public String getStackTrace() {
var stackTrace = new StringBuilder();
StackTraceElement[] elements = thread.getStackTrace();
for (int i = 0; i < elements.length; ++i) {
var element = elements[i];
stackTrace.append(element.getClassName())
.append('.')
.append(element.getMethodName())
.append('(')
.append(element.getFileName())
.append(':')
.append(element.getLineNumber())
.append(")\n");
}
return stackTrace.toString();
}
public List<LockInfo> getLockInfos() { return List.copyOf(lockInfos); }
/** Mutable method (see class doc) */
public void invokingAcquire(Duration timeout) {
lockCountersForPath.invokeAcquireCount.incrementAndGet();
lockCountersForPath.inCriticalRegionCount.incrementAndGet();
lockInfos.add(LockInfo.invokingAcquire(this, timeout));
}
/** Mutable method (see class doc) */
public void acquireFailed() {
removeLastLockInfo(lockCountersForPath.acquireFailedCount, LockInfo::acquireFailed);
}
/** Mutable method (see class doc) */
public void acquireTimedOut() {
if (lockInfos.size() > 1) {
lockCountersForPath.timeoutOnReentrancyErrorCount.incrementAndGet();
}
removeLastLockInfo(lockCountersForPath.acquireTimedOutCount, LockInfo::timedOut);
}
/** Mutable method (see class doc) */
public void lockAcquired() {
lockCountersForPath.lockAcquiredCount.incrementAndGet();
getLastLockInfo().ifPresent(LockInfo::lockAcquired);
}
/** Mutable method (see class doc) */
public void lockReleased() {
removeLastLockInfo(lockCountersForPath.locksReleasedCount, LockInfo::released);
}
private Optional<LockInfo> getLastLockInfo() {
return lockInfos.isEmpty() ? Optional.empty() : Optional.of(lockInfos.peek());
}
private void removeLastLockInfo(AtomicInteger metricToIncrement, Consumer<LockInfo> completeLockInfo) {
metricToIncrement.incrementAndGet();
lockCountersForPath.inCriticalRegionCount.decrementAndGet();
if (lockInfos.isEmpty()) {
lockCountersForPath.noLocksErrorCount.incrementAndGet();
return;
}
LockInfo lockInfo = lockInfos.poll();
completeLockInfo.accept(lockInfo);
synchronized (completedLockInfosMonitor) {
if (completedLockInfos.size() < MAX_COMPLETED_LOCK_INFOS_SIZE) {
lockInfo.fillStackTrace();
completedLockInfos.add(lockInfo);
} else if (lockInfo.getDurationInTerminalStateAndForPriorityQueue()
.compareTo(completedLockInfos.peek().getDurationInTerminalStateAndForPriorityQueue()) > 0) {
completedLockInfos.poll();
lockInfo.fillStackTrace();
completedLockInfos.add(lockInfo);
}
}
}
}
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