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The free Java library for Asterisk PBX integration.
package org.asteriskjava.lock;
import com.google.common.util.concurrent.RateLimiter;
import org.asteriskjava.pbx.util.LogTime;
import org.asteriskjava.util.Log;
import org.asteriskjava.util.LogFactory;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
public class Locker {
private static final Log logger = LogFactory.getLog(Locker.class);
private static volatile boolean diags = false;
private static ScheduledFuture future;
private static final ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
private static final Object sync = new Object();
// keep references to Lockables so they can't be garbage collected between
// reporting intervals
private static final Map keepList = new HashMap<>();
private static final RateLimiter waitRateLimiter = RateLimiter.create(4);
public static LockCloser doWithLock(final Lockable lockable) {
try {
if (diags) {
synchronized (sync) {
keepList.put(lockable.getLockableId(), lockable);
}
return lockWithDiags(lockable);
}
return simpleLock(lockable);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
/**
* determine the caller to Locker
*
* @param lockable
* @return
*/
static String getCaller(Lockable lockable) {
StackTraceElement[] trace = new Exception().getStackTrace();
String name = lockable.getClass().getCanonicalName();
for (StackTraceElement element : trace) {
if (element.getFileName() != null && !element.getFileName().contains(Locker.class.getSimpleName())) {
name = element.getFileName() + " " + element.getMethodName() + " " + element.getLineNumber() + " "
+ element.getClassName();
break;
}
}
return name;
}
public interface LockCloser extends AutoCloseable {
public void close();
}
// Once every ten seconds max
private static RateLimiter warnRateLimiter = RateLimiter.create(0.1);
private static final LogTime startTime = new LogTime();
private static LockCloser simpleLock(Lockable lockable) throws InterruptedException {
LogTime acquireTimer = new LogTime();
ReentrantLock lock = lockable.getInternalLock();
lock.lock();
// lock acquired!
if (acquireTimer.timeTaken() > 1_000 && warnRateLimiter.tryAcquire()) {
logger.warn("Locks are being held for to long, waited " + acquireTimer.timeTaken()
+ "ms, you can enable lock diagnostics by calling Locker.enable()");
}
LogTime holdTimer = new LogTime();
return () -> {
lock.unlock();
if (holdTimer.timeTaken() > 500 && warnRateLimiter.tryAcquire()) {
// don't start warning for the first 10 seconds
if (startTime.timeTaken() > 10_000) {
logger.warn("Locks are being held for to long (" + holdTimer.timeTaken()
+ "ms), you can enable lock diagnostics by calling Locker.enable()");
}
}
};
}
private static LockCloser lockWithDiags(Lockable lockable) throws InterruptedException {
int offset = lockable.addLockRequested();
long waitStart = System.currentTimeMillis();
ReentrantLock lock = lockable.getInternalLock();
while (!lock.tryLock(100, TimeUnit.MILLISECONDS)) {
if (!lockable.isLockDumped() && lockable.getDumpRateLimit().tryAcquire()) {
lockable.setLockDumped(true);
dumpThread(lockable.threadHoldingLock.get(),
"Waiting on lock... blocked by... id:" + lockable.getLockableId());
} else {
if (waitRateLimiter.tryAcquire()) {
long elapsed = System.currentTimeMillis() - waitStart;
logger.warn("waiting " + elapsed + "(MS) id:" + lockable.getLockableId());
}
}
lockable.setLockBlocked(true);
}
lockable.setLockDumped(false);
lockable.addLockAcquired(1);
long acquiredAt = System.currentTimeMillis();
lockable.threadHoldingLock.set(Thread.currentThread());
return new LockCloser() {
@Override
public void close() {
// ignore any wait that may have been caused by Locker code, so
// count the waiters before we release the lock
long waiters = lockable.getLockRequested() - offset;
lockable.addLockWaited((int) waiters);
boolean dumped = lockable.isLockDumped();
// release the lock
lock.unlock();
// count the time waiting and holding the lock
int holdTime = (int) (System.currentTimeMillis() - acquiredAt);
int waitTime = (int) (acquiredAt - waitStart);
lockable.addLockTotalWaitTime(waitTime);
lockable.addLockTotalHoldTime(holdTime);
long averageHoldTime = lockable.getLockAverageHoldTime();
if ((waiters > 0 && holdTime > averageHoldTime * 2) || dumped) {
// some threads waited
String message = "Lock held for (" + holdTime + "MS), " + waiters
+ " threads waited for some of that time! " + getCaller(lockable) + " id:"
+ lockable.getLockableId();
logger.warn(message);
if (holdTime > averageHoldTime * 10.0 || dumped) {
Exception trace = new Exception(message);
logger.error(trace, trace);
}
}
if (holdTime > averageHoldTime * 5.0) {
// long hold!
String message = "Lock hold of lock (" + holdTime + "MS), average is "
+ lockable.getLockAverageHoldTime() + " " + getCaller(lockable) + " id:"
+ lockable.getLockableId();
logger.warn(message);
if (holdTime > averageHoldTime * 10.0) {
Exception trace = new Exception(message);
logger.error(trace, trace);
}
}
}
};
}
public static void dumpThread(Thread thread, String message) {
if (thread != null) {
StackTraceElement[] trace = thread.getStackTrace();
String dump = "";
int i = 0;
for (; i < trace.length; i++) {
StackTraceElement ste = trace[i];
dump += "\tat " + ste.toString();
dump += '\n';
}
logger.error(message);
if (dump.length() > 0) {
logger.error(dump);
} else {
logger.error("Unable to create dump, thread seems to have exited.");
}
} else {
logger.error("Thread hasn't been set: " + message);
}
}
/**
* start dumping lock stats once per minute, can't be stopped once started.
*/
public static void enable() {
synchronized (sync) {
if (!diags) {
diags = true;
future = executor.scheduleWithFixedDelay(() -> {
dumpStats();
}, 1, 1, TimeUnit.MINUTES);
logger.warn("Lock checking enabled");
} else {
logger.warn("Already enabled");
}
}
}
public static void disable() {
synchronized (sync) {
if (diags) {
diags = false;
future.cancel(false);
dumpStats();
logger.warn("Lock checking disabled");
} else {
logger.warn("Lock checking is already disabled");
}
}
}
private static volatile boolean first = true;
static void dumpStats() {
List lockables = new LinkedList<>();
synchronized (sync) {
lockables.addAll(keepList.values());
keepList.clear();
}
boolean activity = false;
for (Lockable lockable : lockables) {
if (lockable.wasLockBlocked()) {
int waited = lockable.getLockWaited();
int waitTime = lockable.getLockTotalWaitTime();
int acquired = lockable.getLockAcquired();
int holdTime = lockable.getLockTotalHoldTime();
lockable.setLockBlocked(false);
activity = true;
logger.warn(lockable.asLockString());
lockable.addLockWaited(-waited);
lockable.addLockTotalWaitTime(-waitTime);
lockable.addLockAcquired(-acquired);
lockable.addLockTotalHoldTime(-holdTime);
}
}
if (first || activity) {
logger.warn("Will dump Lock stats each minute when there is contention...");
first = false;
}
}
}