/*
* 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.atomic;
import org.infinispan.AdvancedCache;
import org.infinispan.batch.AutoBatchSupport;
import org.infinispan.container.entries.CacheEntry;
import org.infinispan.context.Flag;
import org.infinispan.context.FlagContainer;
import org.infinispan.marshall.MarshalledValue;
import org.infinispan.transaction.LocalTransaction;
import org.infinispan.transaction.TransactionTable;
import org.infinispan.util.logging.Log;
import org.infinispan.util.logging.LogFactory;
import javax.transaction.SystemException;
import javax.transaction.Transaction;
import javax.transaction.TransactionManager;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.Set;
/**
* A layer of indirection around an {@link AtomicHashMap} to provide consistency and isolation for concurrent readers
* while writes may also be going on. The techniques used in this implementation are very similar to the lock-free
* reader MVCC model used in the {@link org.infinispan.container.entries.MVCCEntry} implementations for the core data
* container, which closely follow software transactional memory approaches to dealing with concurrency.
* <br /><br />
* Implementations of this class are rarely created on their own; {@link AtomicHashMap#getProxy(org.infinispan.AdvancedCache, Object, boolean)}
* should be used to retrieve an instance of this proxy.
* <br /><br />
* Typically proxies are only created by the {@link AtomicMapLookup} helper, and would not be created by end-user code
* directly.
*
* @author Manik Surtani
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
* @see AtomicHashMap
* @since 4.0
*/
public class AtomicHashMapProxy<K, V> extends AutoBatchSupport implements AtomicMap<K, V> {
private static final Log log = LogFactory.getLog(AtomicHashMapProxy.class);
private static final boolean trace = log.isTraceEnabled();
protected final Object deltaMapKey;
protected final AdvancedCache<Object, AtomicMap<K, V>> cache;
protected volatile boolean startedReadingMap = false;
protected final FlagContainer flagContainer;
protected TransactionTable transactionTable;
protected TransactionManager transactionManager;
AtomicHashMapProxy(AdvancedCache<Object, AtomicMap<K, V>> cache, Object deltaMapKey) {
this(cache, deltaMapKey, null);
}
AtomicHashMapProxy(AdvancedCache<?, ?> cache, Object deltaMapKey, FlagContainer flagContainer) {
this.cache = (AdvancedCache<Object, AtomicMap<K, V>>) cache;
this.deltaMapKey = deltaMapKey;
this.batchContainer = cache.getBatchContainer();
this.flagContainer = flagContainer;
transactionTable = cache.getComponentRegistry().getComponent(TransactionTable.class);
transactionManager = cache.getTransactionManager();
}
@SuppressWarnings("unchecked")
protected AtomicHashMap<K, V> toMap(Object object) {
Object map = (object instanceof MarshalledValue) ? ((MarshalledValue) object).get() : object;
return (AtomicHashMap<K, V>) map;
}
// internal helper, reduces lots of casts.
protected AtomicHashMap<K, V> getDeltaMapForRead() {
AtomicHashMap<K, V> ahm = toMap(cache.get(deltaMapKey));
if (ahm != null && !startedReadingMap) startedReadingMap = true;
assertValid(ahm);
return ahm;
}
/**
* Looks up the CacheEntry stored in transactional context corresponding to this AtomicMap. If this AtomicMap
* has yet to be touched by the current transaction, this method will return a null.
* @return
*/
protected CacheEntry lookupEntryFromCurrentTransaction() {
// Prior to 5.1, this used to happen by grabbing any InvocationContext in ThreadLocal. Since ThreadLocals
// can no longer be relied upon in 5.1, we need to grab the TransactionTable and check if an ongoing
// transaction exists, peeking into transactional state instead.
try {
Transaction tx = transactionManager.getTransaction();
LocalTransaction localTransaction = tx == null ? null : transactionTable.getLocalTransaction(tx);
// The stored localTransaction could be null, if this is the first call in a transaction. In which case
// we know that there is no transactional state to refer to - i.e., no entries have been looked up as yet.
return localTransaction == null ? null : localTransaction.lookupEntry(deltaMapKey);
} catch (SystemException e) {
return null;
}
}
@SuppressWarnings("unchecked")
protected AtomicHashMap<K, V> getDeltaMapForWrite() {
CacheEntry lookedUpEntry = lookupEntryFromCurrentTransaction();
boolean lockedAndCopied = lookedUpEntry != null && lookedUpEntry.isChanged() &&
toMap(lookedUpEntry.getValue()).copied;
if (lockedAndCopied) {
return getDeltaMapForRead();
} else {
// acquire WL
boolean suppressLocks = flagContainer != null && flagContainer.hasFlag(Flag.SKIP_LOCKING);
if (!suppressLocks && flagContainer != null) flagContainer.setFlags(Flag.FORCE_WRITE_LOCK);
if (trace) {
if (suppressLocks)
log.trace("Skip locking flag used. Skipping locking.");
else
log.trace("Forcing write lock even for reads");
}
// reinstate the flag
if (suppressLocks) flagContainer.setFlags(Flag.SKIP_LOCKING);
AtomicHashMap<K, V> map = getDeltaMapForRead();
// copy for write
AtomicHashMap<K, V> copy = map == null ? new AtomicHashMap<K, V>(true) : map.copy();
copy.initForWriting();
cache.put(deltaMapKey, copy);
return copy;
}
}
// readers
protected void assertValid(AtomicHashMap<?, ?> map) {
if (startedReadingMap && (map == null || map.removed)) throw new IllegalStateException("AtomicMap stored under key " + deltaMapKey + " has been concurrently removed!");
}
@Override
public Set<K> keySet() {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null ? Collections.<K>emptySet() : map.keySet();
}
@Override
public Collection<V> values() {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null ? Collections.<V>emptySet() : map.values();
}
@Override
public Set<Entry<K, V>> entrySet() {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null ? Collections.<Entry<K,V>>emptySet() : map.entrySet();
}
@Override
public int size() {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null ? 0 : map.size();
}
@Override
public boolean isEmpty() {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null || map.isEmpty();
}
@Override
public boolean containsKey(Object key) {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map != null && map.containsKey(key);
}
@Override
public boolean containsValue(Object value) {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map != null && map.containsValue(value);
}
@Override
public V get(Object key) {
AtomicHashMap<K, V> map = getDeltaMapForRead();
return map == null ? null : map.get(key);
}
//writers
@Override
public V put(K key, V value) {
AtomicHashMap<K, V> deltaMapForWrite;
try {
startAtomic();
deltaMapForWrite = getDeltaMapForWrite();
return deltaMapForWrite.put(key, value);
}
finally {
endAtomic();
}
}
@Override
public V remove(Object key) {
AtomicHashMap<K, V> deltaMapForWrite;
try {
startAtomic();
deltaMapForWrite = getDeltaMapForWrite();
return deltaMapForWrite.remove(key);
}
finally {
endAtomic();
}
}
@Override
public void putAll(Map<? extends K, ? extends V> m) {
AtomicHashMap<K, V> deltaMapForWrite;
try {
startAtomic();
deltaMapForWrite = getDeltaMapForWrite();
deltaMapForWrite.putAll(m);
}
finally {
endAtomic();
}
}
@Override
public void clear() {
AtomicHashMap<K, V> deltaMapForWrite;
try {
startAtomic();
deltaMapForWrite = getDeltaMapForWrite();
deltaMapForWrite.clear();
} finally {
endAtomic();
}
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder("AtomicHashMapProxy{deltaMapKey=");
sb.append(deltaMapKey);
sb.append("}");
return sb.toString();
}
}