/*
*
* * Copyright 2014 Orient Technologies LTD (info(at)orientechnologies.com)
* *
* * Licensed under the Apache License, Version 2.0 (the "License");
* * you may not use this file except in compliance with the License.
* * You may obtain a copy of the License at
* *
* * http://www.apache.org/licenses/LICENSE-2.0
* *
* * Unless required by applicable law or agreed to in writing, software
* * distributed under the License is distributed on an "AS IS" BASIS,
* * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* * See the License for the specific language governing permissions and
* * limitations under the License.
* *
* * For more information: http://www.orientechnologies.com
*
*/
package com.orientechnologies.common.concur.resource;
import com.orientechnologies.common.concur.OTimeoutException;
import com.orientechnologies.common.concur.lock.OLockException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.IdentityHashMap;
import java.util.Set;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Adaptive class to handle shared resources. It's configurable specifying if it's running in a concurrent environment and allow o
* specify a maximum timeout to avoid deadlocks.
*
* @author Luca Garulli (l.garulli--at--orientechnologies.com)
*
*/
public class OSharedResourceAdaptive {
private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
private final AtomicInteger users = new AtomicInteger(0);
private final boolean concurrent;
private final int timeout;
private final boolean ignoreThreadInterruption;
private int scaledUpCount = 0;
protected OSharedResourceAdaptive() {
this.concurrent = true;
this.timeout = 0;
this.ignoreThreadInterruption = false;
}
protected OSharedResourceAdaptive(final int iTimeout) {
this.concurrent = true;
this.timeout = iTimeout;
this.ignoreThreadInterruption = false;
}
protected OSharedResourceAdaptive(final boolean iConcurrent) {
this.concurrent = iConcurrent;
this.timeout = 0;
this.ignoreThreadInterruption = false;
}
protected OSharedResourceAdaptive(final boolean iConcurrent, final int iTimeout, boolean ignoreThreadInterruption) {
this.concurrent = iConcurrent;
this.timeout = iTimeout;
this.ignoreThreadInterruption = ignoreThreadInterruption;
}
public int getUsers() {
return users.get();
}
public int addUser() {
return users.incrementAndGet();
}
public int removeUser() {
if (users.get() < 1)
throw new IllegalStateException("Cannot remove user of the shared resource " + toString() + " because no user is using it");
return users.decrementAndGet();
}
public boolean isConcurrent() {
return concurrent;
}
/** To use in assert block. */
public boolean assertExclusiveLockHold() {
return lock.getWriteHoldCount() > 0;
}
/** To use in assert block. */
public boolean assertSharedLockHold() {
return lock.getReadHoldCount() > 0;
}
protected void acquireExclusiveLock() {
if (concurrent)
if (timeout > 0) {
try {
if (lock.writeLock().tryLock(timeout, TimeUnit.MILLISECONDS))
// OK
return;
} catch (InterruptedException e) {
if (ignoreThreadInterruption) {
// IGNORE THE THREAD IS INTERRUPTED: TRY TO RE-LOCK AGAIN
try {
if (lock.writeLock().tryLock(timeout, TimeUnit.MILLISECONDS)) {
// OK, RESET THE INTERRUPTED STATE
Thread.currentThread().interrupt();
return;
}
} catch (InterruptedException e2) {
Thread.currentThread().interrupt();
}
}
throw new OLockException("Thread interrupted while waiting for resource of class '" + getClass() + "' with timeout="
+ timeout);
}
throwTimeoutException(lock.writeLock());
} else {
lock.writeLock().lock();
}
}
protected boolean tryAcquireExclusiveLock() {
return !concurrent || lock.writeLock().tryLock();
}
protected void acquireSharedLock() {
if (concurrent)
if (timeout > 0) {
try {
if (lock.readLock().tryLock(timeout, TimeUnit.MILLISECONDS))
// OK
return;
} catch (InterruptedException e) {
if (ignoreThreadInterruption) {
// IGNORE THE THREAD IS INTERRUPTED: TRY TO RE-LOCK AGAIN
try {
if (lock.readLock().tryLock(timeout, TimeUnit.MILLISECONDS)) {
// OK, RESET THE INTERRUPTED STATE
Thread.currentThread().interrupt();
return;
}
} catch (InterruptedException e2) {
Thread.currentThread().interrupt();
}
}
throw new OLockException("Thread interrupted while waiting for resource of class '" + getClass() + "' with timeout="
+ timeout);
}
throwTimeoutException(lock.readLock());
} else
lock.readLock().lock();
}
protected boolean tryAcquireSharedLock() {
return !concurrent || lock.readLock().tryLock();
}
protected void releaseExclusiveLock() {
if (concurrent) {
lock.writeLock().unlock();
}
}
protected void releaseSharedLock() {
if (concurrent)
lock.readLock().unlock();
}
private void throwTimeoutException(Lock lock) {
final String owner = extractLockOwnerStackTrace(lock);
throw new OTimeoutException("Timeout on acquiring exclusive lock against resource of class: " + getClass() + " with timeout="
+ timeout + (owner != null ? "\n" + owner : ""));
}
private String extractLockOwnerStackTrace(Lock lock) {
try {
Field syncField = lock.getClass().getDeclaredField("sync");
syncField.setAccessible(true);
Object sync = syncField.get(lock);
Method getOwner = sync.getClass().getSuperclass().getDeclaredMethod("getOwner");
getOwner.setAccessible(true);
final Thread owner = (Thread) getOwner.invoke(sync);
if (owner == null)
return null;
StringWriter stringWriter = new StringWriter();
PrintWriter printWriter = new PrintWriter(stringWriter);
printWriter.append("Owner thread : ").append(owner.toString()).append("\n");
StackTraceElement[] stackTrace = owner.getStackTrace();
for (StackTraceElement traceElement : stackTrace)
printWriter.println("\tat " + traceElement);
printWriter.flush();
return stringWriter.toString();
} catch (RuntimeException e) {
return null;
} catch (NoSuchFieldException e) {
return null;
} catch (IllegalAccessException e) {
return null;
} catch (NoSuchMethodException e) {
return null;
} catch (InvocationTargetException e) {
return null;
}
}
}