/*
* JBoss, Home of Professional Open Source
* Copyright 2009 Red Hat Inc. and/or its affiliates and other
* contributors as indicated by the @author tags. All rights reserved.
* See the copyright.txt in the distribution for a full listing of
* individual contributors.
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* This software is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this software; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA, or see the FSF site: http://www.fsf.org.
*/
package org.infinispan.loaders;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import java.util.Set;
import org.infinispan.Cache;
import org.infinispan.container.entries.InternalCacheEntry;
import org.infinispan.marshall.StreamingMarshaller;
import org.infinispan.util.concurrent.locks.StripedLock;
import org.infinispan.util.logging.Log;
import org.infinispan.util.logging.LogFactory;
/**
* This class extends {@link AbstractCacheStore} adding lock support for consistently accessing stored data.
* <p/>
* In-memory locking is needed by aggregation operations(e.g. loadAll, toStream, fromStream) to make sure that
* manipulated data won't be corrupted by concurrent access to Store. It also assures atomic data access for each stored
* entry.
* <p/>
* Locking is based on a {@link StripedLock}. You can tune the concurrency level of the striped lock (see the Javadocs
* of StripedLock for details on what this is) by using the {@link LockSupportCacheStoreConfig#setLockConcurrencyLevel(int)}
* setter.
* <p/>
*
* @author Mircea.Markus@jboss.com
* @author <a href="http://gleamynode.net/">Trustin Lee</a>
*
* @param <L> the type of the locking key returned by
* {@link #getLockFromKey(Object)}
*/
public abstract class LockSupportCacheStore<L> extends AbstractCacheStore {
private static final Log log = LogFactory.getLog(LockSupportCacheStore.class);
private static final boolean trace = log.isTraceEnabled();
private StripedLock locks;
private long globalLockTimeoutMillis;
private LockSupportCacheStoreConfig config;
@Override
public void init(CacheLoaderConfig config, Cache<?, ?> cache, StreamingMarshaller m) throws CacheLoaderException {
super.init(config, cache, m);
this.config = (LockSupportCacheStoreConfig) config;
}
@Override
public void start() throws CacheLoaderException {
super.start();
if (config == null) {
throw new CacheLoaderException("Null config. Possible reason is not calling super.init(...)");
}
log.tracef("Starting cache with config: %s", config);
locks = new StripedLock(config.getLockConcurrencyLevel());
globalLockTimeoutMillis = config.getLockAcquistionTimeout();
}
/**
* Release the locks (either read or write).
*/
protected final void unlock(L key) {
locks.releaseLock(key);
}
/**
* Acquires write lock on the given key.
*/
protected final void lockForWriting(L key) {
locks.acquireLock(key, true);
}
/**
* Acquires read lock on the given key.
*/
protected final void lockForReading(L key) {
locks.acquireLock(key, false);
}
/**
* Upgrades a read lock to a write lock.
*/
protected final void upgradeLock(L key) {
locks.upgradeLock(key);
}
/**
* Downgrade a write lock to a read lock
*/
protected final void downgradeLock(L key) {
locks.downgradeLock(key);
}
/**
* Same as {@link #lockForWriting(Object)}, but with 0 timeout.
*/
protected final boolean immediateLockForWriting(L key) {
return locks.acquireLock(key, true, 0);
}
/**
* Based on the supplied param, acquires a global read(false) or write (true) lock.
*/
protected final boolean acquireGlobalLock(boolean exclusive) {
return locks.acquireGlobalLock(exclusive, globalLockTimeoutMillis);
}
/**
* Based on the supplied param, releases a global read(false) or write (true) lock.
*/
protected final void releaseGlobalLock(boolean exclusive) {
locks.releaseGlobalLock(exclusive);
}
@Override
public final InternalCacheEntry load(Object key) throws CacheLoaderException {
L lockingKey = getLockFromKey(key);
lockForReading(lockingKey);
try {
return loadLockSafe(key, lockingKey);
} finally {
unlock(lockingKey);
}
}
@Override
public final Set<InternalCacheEntry> loadAll() throws CacheLoaderException {
acquireGlobalLock(false);
try {
return loadAllLockSafe();
} finally {
releaseGlobalLock(false);
}
}
@Override
public final Set<InternalCacheEntry> load(int maxEntries) throws CacheLoaderException {
if (maxEntries < 0) {
return loadAll();
}
acquireGlobalLock(false);
try {
return loadLockSafe(maxEntries);
} finally {
releaseGlobalLock(false);
}
}
@Override
public Set<Object> loadAllKeys(Set<Object> keysToExclude) throws CacheLoaderException {
acquireGlobalLock(false);
try {
return loadAllKeysLockSafe(keysToExclude);
} finally {
releaseGlobalLock(false);
}
}
@Override
public final void store(InternalCacheEntry ed) throws CacheLoaderException {
if (trace) {
log.tracef("store(%s)", ed);
}
if (ed == null) {
return;
}
if (ed.canExpire() && ed.isExpired(System.currentTimeMillis())) {
if (containsKey(ed.getKey())) {
if (trace) {
log.tracef("Entry %s is expired! Removing!", ed);
}
remove(ed.getKey());
} else {
if (trace) {
log.tracef("Entry %s is expired! Not doing anything.", ed);
}
}
return;
}
L keyHashCode = getLockFromKey(ed.getKey());
lockForWriting(keyHashCode);
try {
storeLockSafe(ed, keyHashCode);
} finally {
unlock(keyHashCode);
}
if (trace) {
log.tracef("exit store(%s)", ed);
}
}
@Override
public final boolean remove(Object key) throws CacheLoaderException {
if (trace) {
log.tracef("remove(%s)", key);
}
L keyHashCode = getLockFromKey(key);
try {
lockForWriting(keyHashCode);
return removeLockSafe(key, keyHashCode);
} finally {
unlock(keyHashCode);
if (trace) {
log.tracef("Exit remove(%s)", key);
}
}
}
@Override
public final void fromStream(ObjectInput objectInput) throws CacheLoaderException {
try {
acquireGlobalLock(true);
fromStreamLockSafe(objectInput);
} finally {
releaseGlobalLock(true);
}
}
@Override
public void toStream(ObjectOutput objectOutput) throws CacheLoaderException {
try {
acquireGlobalLock(false);
toStreamLockSafe(objectOutput);
} finally {
releaseGlobalLock(false);
}
}
@Override
public final void clear() throws CacheLoaderException {
if (trace) {
log.trace("Clearing store");
}
try {
acquireGlobalLock(true);
clearLockSafe();
} finally {
releaseGlobalLock(true);
}
}
public int getTotalLockCount() {
return locks.getTotalLockCount();
}
protected abstract void clearLockSafe() throws CacheLoaderException;
protected abstract Set<InternalCacheEntry> loadAllLockSafe() throws CacheLoaderException;
protected abstract Set<InternalCacheEntry> loadLockSafe(int maxEntries) throws CacheLoaderException;
protected abstract Set<Object> loadAllKeysLockSafe(Set<Object> keysToExclude) throws CacheLoaderException;
protected abstract void toStreamLockSafe(ObjectOutput oos) throws CacheLoaderException;
protected abstract void fromStreamLockSafe(ObjectInput ois) throws CacheLoaderException;
protected abstract boolean removeLockSafe(Object key, L lockingKey) throws CacheLoaderException;
protected abstract void storeLockSafe(InternalCacheEntry ed, L lockingKey) throws CacheLoaderException;
protected abstract InternalCacheEntry loadLockSafe(Object key, L lockingKey) throws CacheLoaderException;
protected abstract L getLockFromKey(Object key) throws CacheLoaderException;
}