org.eclipse.persistence.internal.helper.ReadLockManager Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of eclipselink Show documentation
Show all versions of eclipselink Show documentation
EclipseLink build based upon Git transaction f2b9fc5
/*
* Copyright (c) 2021 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Oracle - initial API and implementation
package org.eclipse.persistence.internal.helper;
import org.eclipse.persistence.internal.helper.type.ReadLockAcquisitionMetadata;
import java.util.*;
public class ReadLockManager {
public static final int FIRST_INDEX_OF_COLLECTION = 0;
/**
* This vector of read locks is essentially a basket of cache keys (classes that extend concurrency manager) that a
* specific thread has acquired for reading. We need to create this additional logic in order to be able to reduce
* the readers count on a cache key whenever
*
*/
private final Vector readLocks = new Vector<>(1);
/**
* We have seen that the read locks vector we have is very insufficient. We keep it for now due to the tracing code
* that is making use of it. But we also want to have a new tracing map with a lot more metadata
*/
private final Map> mapThreadToReadLockAcquisitionMetadata = new HashMap<>();
/**
* This is a field that will never be cleared. It will be getting ADDs if any problem is detected when we try remove
* a read lock from our tracing.
*/
private final List removeReadLockProblemsDetected = new ArrayList<>();
/**
* add a concurrency manager as deferred locks to the DLM
*/
public synchronized void addReadLock(ConcurrencyManager concurrencyManager) {
final Thread currentThread = Thread.currentThread();
final long currentThreadId = currentThread.getId();
ReadLockAcquisitionMetadata readLockAcquisitionMetadata = ConcurrencyUtil.SINGLETON.createReadLockAcquisitionMetadata(concurrencyManager);
this.readLocks.add(FIRST_INDEX_OF_COLLECTION, concurrencyManager);
if(!mapThreadToReadLockAcquisitionMetadata.containsKey(currentThreadId)) {
List newList = Collections.synchronizedList(new ArrayList());
mapThreadToReadLockAcquisitionMetadata.put(currentThreadId, newList );
}
List acquiredReadLocksInCurrentTransactionList = mapThreadToReadLockAcquisitionMetadata.get(currentThreadId);
acquiredReadLocksInCurrentTransactionList.add(FIRST_INDEX_OF_COLLECTION, readLockAcquisitionMetadata);
}
/**
* During normal operation of the concurrency manager, each time a cache key is decrement in the number of readers,
* so must the corresponding read lock manager of the thread be told let go of the cache key object acquired for
* reading.
*
* @param concurrencyManager
* the concurrency cache key that is about to be decrement in number of readers.
*/
public synchronized void removeReadLock(ConcurrencyManager concurrencyManager) {
final Thread currentThread = Thread.currentThread();
final long currentThreadId = currentThread.getId();
boolean readLockManagerHasTracingAboutAddedReadLocksForCurrentThread = mapThreadToReadLockAcquisitionMetadata.containsKey(currentThreadId);
if (!readLockManagerHasTracingAboutAddedReadLocksForCurrentThread) {
String errorMessage = ConcurrencyUtil.SINGLETON.readLockManagerProblem02ReadLockManageHasNoEntriesForThread(concurrencyManager, currentThreadId);
removeReadLockProblemsDetected.add(errorMessage);
return;
}
List readLocksAcquiredDuringCurrentThread = mapThreadToReadLockAcquisitionMetadata.get(currentThreadId);
ReadLockAcquisitionMetadata readLockAquisitionMetadataToRemove = null;
for (ReadLockAcquisitionMetadata currentReadLockAcquisitionMetadata : readLocksAcquiredDuringCurrentThread) {
ConcurrencyManager currentCacheKeyObjectToCheck = currentReadLockAcquisitionMetadata.getCacheKeyWhoseNumberOfReadersThreadIsIncrementing();
boolean dtoToRemoveFound = concurrencyManager.getConcurrencyManagerId() == currentCacheKeyObjectToCheck.getConcurrencyManagerId();
if (dtoToRemoveFound) {
readLockAquisitionMetadataToRemove = currentReadLockAcquisitionMetadata;
break;
}
}
if (readLockAquisitionMetadataToRemove == null) {
String errorMessage = ConcurrencyUtil.SINGLETON.readLockManagerProblem03ReadLockManageHasNoEntriesForThread(concurrencyManager, currentThreadId);
removeReadLockProblemsDetected.add(errorMessage);
return;
}
this.readLocks.remove(concurrencyManager);
readLocksAcquiredDuringCurrentThread.remove(readLockAquisitionMetadataToRemove);
if (readLocksAcquiredDuringCurrentThread.isEmpty()) {
mapThreadToReadLockAcquisitionMetadata.remove(currentThreadId);
}
}
/**
* Return a set of the deferred locks
*/
public synchronized List getReadLocks() {
return Collections.unmodifiableList(readLocks);
}
/**
* Allow the concurrency manager to directly pump a message stating that there was a problem while decrementing the
* number of readers.
*
* @param problemDetected
* the detected problem
*/
public synchronized void addRemoveReadLockProblemsDetected(String problemDetected) {
removeReadLockProblemsDetected.add(problemDetected);
}
/** Getter for {@link #mapThreadToReadLockAcquisitionMetadata} */
public Map> getMapThreadToReadLockAcquisitionMetadata() {
return mapThreadToReadLockAcquisitionMetadata;
}
/** Getter for {@link #removeReadLockProblemsDetected} */
public List getRemoveReadLockProblemsDetected() {
return removeReadLockProblemsDetected;
}
/**
* True if the tracing the data on the object has been completely removed. If this is the case it is perfectly fine
* to remove the read lock manager from from the hash map of Thread To tis ReadLockManager Tracing.
*
* @return true if the current read lock manger contains no information about acquired locks that were never
* released or any errors detected while attempting to remove a cache key. If there is any error detected or
* any read lock acquired in the tracing we definitely do not want this object instance to be thrown out
* from our main tracing. It is probably revealing problems in read lock acquisition and released.
*/
public synchronized boolean isEmpty() {
return readLocks.isEmpty() && removeReadLockProblemsDetected.isEmpty();
}
/**
* Create a new instance {@link ReadLockManager} that is in all regards
* equal to the current instance.
*
* USE CASE:
* This method is meant to be used by algorithms
* that want to dump a snapshot of the current state of the system
* or to go about doing
*/
@SuppressWarnings("unchecked")
@Override
public synchronized ReadLockManager clone() {
ReadLockManager clone = new ReadLockManager();
clone.readLocks.addAll(this.readLocks);
for (Map.Entry> currentEntry : this.mapThreadToReadLockAcquisitionMetadata.entrySet()) {
Long key = currentEntry.getKey();
List value = currentEntry.getValue();
clone.mapThreadToReadLockAcquisitionMetadata.put(key, new ArrayList<>(value));
}
clone.removeReadLockProblemsDetected.addAll(this.removeReadLockProblemsDetected);
return clone;
}
}