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A module of the Hibernate Core project
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2009, Red Hat, Inc or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Middleware LLC.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program 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 distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.cache.infinispan.access;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
import javax.transaction.SystemException;
import javax.transaction.Transaction;
import javax.transaction.TransactionManager;
import org.hibernate.cache.CacheException;
import org.hibernate.cache.infinispan.InfinispanRegionFactory;
import org.infinispan.AdvancedCache;
import org.infinispan.manager.EmbeddedCacheManager;
/**
* Encapsulates logic to allow a {@link TransactionalAccessDelegate} to determine
* whether a {@link TransactionalAccessDelegate#putFromLoad(Object, Object, long, Object, boolean)}
* call should be allowed to update the cache. A putFromLoad has
* the potential to store stale data, since the data may have been removed from the
* database and the cache between the time when the data was read from the database
* and the actual call to putFromLoad.
*
* The expected usage of this class by a thread that read the cache and did
* not find data is:
*
*
* - Call {@link #registerPendingPut(Object)}
* - Read the database
* - Call {@link #acquirePutFromLoadLock(Object)}
*
- if above returns
false, the thread should not cache the data;
* only if above returns true, put data in the cache and...
* - then call {@link #releasePutFromLoadLock(Object)}
*
*
*
*
* The expected usage by a thread that is taking an action such that any pending
* putFromLoad may have stale data and should not cache it is to either
* call
*
*
* - {@link #invalidateKey(Object)} (for a single key invalidation)
* - or {@link #invalidateRegion()} (for a general invalidation all pending puts)
*
*
*
*
* This class also supports the concept of "naked puts", which are calls to
* {@link #acquirePutFromLoadLock(Object)} without a preceding {@link #registerPendingPut(Object)}
* call.
*
*
* @author Brian Stansberry
*
* @version $Revision: $
*/
public class PutFromLoadValidator {
/**
* Period (in ms) after a removal during which a call to
* {@link #acquirePutFromLoadLock(Object)} that hasn't been
* {@link #registerPendingPut(Object) pre-registered} (aka a "naked put")
* will return false.
* will return false.
*/
public static final long NAKED_PUT_INVALIDATION_PERIOD = TimeUnit.SECONDS.toMillis(20);
/**
* Used to determine whether the owner of a pending put is a thread or a transaction
*/
private final TransactionManager transactionManager;
private final long nakedPutInvalidationPeriod;
/**
* Registry of expected, future, isPutValid calls. If a key+owner is registered in this map, it
* is not a "naked put" and is allowed to proceed.
*/
private final ConcurrentMap pendingPuts;
private final ConcurrentMap recentRemovals = new ConcurrentHashMap();
/**
* List of recent removals. Used to ensure we don't leak memory via the recentRemovals map
*/
private final List removalsQueue = new LinkedList();
/**
* The time when the first element in removalsQueue will expire. No reason to do housekeeping on
* the queue before this time.
*/
private volatile long earliestRemovalTimestamp;
/** Lock controlling access to removalsQueue */
private final Lock removalsLock = new ReentrantLock();
/**
* The time of the last call to regionRemoved(), plus NAKED_PUT_INVALIDATION_PERIOD. All naked
* puts will be rejected until the current time is greater than this value.
*/
private volatile long invalidationTimestamp;
/**
* Creates a new PutFromLoadValidator.
*/
public PutFromLoadValidator(AdvancedCache cache) {
this(cache, NAKED_PUT_INVALIDATION_PERIOD);
}
/**
* Constructor variant for use by unit tests; allows control of various timeouts by the test.
*/
public PutFromLoadValidator(AdvancedCache cache,
long nakedPutInvalidationPeriod) {
this(cache.getCacheManager(), cache.getTransactionManager(),
nakedPutInvalidationPeriod);
}
public PutFromLoadValidator(EmbeddedCacheManager cacheManager,
TransactionManager tm, long nakedPutInvalidationPeriod) {
this.pendingPuts = cacheManager
.getCache(InfinispanRegionFactory.PENDING_PUTS_CACHE_NAME);
this.transactionManager = tm;
this.nakedPutInvalidationPeriod = nakedPutInvalidationPeriod;
}
// ----------------------------------------------------------------- Public
/**
* Acquire a lock giving the calling thread the right to put data in the
* cache for the given key.
*
* NOTE: A call to this method that returns true
* should always be matched with a call to {@link #releasePutFromLoadLock(Object)}.
*
*
* @param key the key
*
* @return true if the lock is acquired and the cache put
* can proceed; false if the data should not be cached
*/
public boolean acquirePutFromLoadLock(Object key) {
boolean valid = false;
boolean locked = false;
long now = System.currentTimeMillis();
try {
PendingPutMap pending = pendingPuts.get(key);
if (pending != null) {
locked = pending.acquireLock(100, TimeUnit.MILLISECONDS);
if (locked) {
try {
PendingPut toCancel = pending.remove(getOwnerForPut());
if (toCancel != null) {
valid = !toCancel.completed;
toCancel.completed = true;
}
}
finally {
if (!valid) {
pending.releaseLock();
locked = false;
}
}
}
}
else {
// Key wasn't in pendingPuts, so either this is a "naked put"
// or regionRemoved has been called. Check if we can proceed
if (now > invalidationTimestamp) {
Long removedTime = recentRemovals.get(key);
if (removedTime == null || now > removedTime ) {
// It's legal to proceed. But we have to record this key
// in pendingPuts so releasePutFromLoadLock can find it.
// To do this we basically simulate a normal "register
// then acquire lock" pattern
registerPendingPut(key);
locked = acquirePutFromLoadLock(key);
valid = locked;
}
}
}
}
catch (Throwable t) {
if (locked) {
PendingPutMap toRelease = pendingPuts.get(key);
if (toRelease != null) {
toRelease.releaseLock();
}
}
if (t instanceof RuntimeException) {
throw (RuntimeException) t;
} else if (t instanceof Error) {
throw (Error) t;
} else {
throw new RuntimeException(t);
}
}
return valid;
}
/**
* Releases the lock previously obtained by a call to
* {@link #acquirePutFromLoadLock(Object)} that returned true.
*
* @param key the key
*/
public void releasePutFromLoadLock(Object key) {
PendingPutMap pending = pendingPuts.get(key);
if (pending != null) {
if (pending.size() == 0) {
pendingPuts.remove(key, pending);
}
pending.releaseLock();
}
}
/**
* Invalidates any {@link #registerPendingPut(Object) previously registered pending puts} ensuring a subsequent call to
* {@link #acquirePutFromLoadLock(Object)} will return false. This method will block until any
* concurrent thread that has {@link #acquirePutFromLoadLock(Object) acquired the putFromLoad lock} for the given key
* has released the lock. This allows the caller to be certain the putFromLoad will not execute after this method
* returns, possibly caching stale data.
*
* @param key key identifying data whose pending puts should be invalidated
* @return true if the invalidation was successful; false if a problem occured (which the
* caller should treat as an exception condition)
*/
public boolean invalidateKey(Object key) {
boolean success = true;
// Invalidate any pending puts
PendingPutMap pending = pendingPuts.get(key);
if (pending != null) {
// This lock should be available very quickly, but we'll be
// very patient waiting for it as callers should treat not
// acquiring it as an exception condition
if (pending.acquireLock(60, TimeUnit.SECONDS)) {
try {
pending.invalidate();
}
finally {
pending.releaseLock();
}
} else {
success = false;
}
}
// Record when this occurred to invalidate later naked puts
RecentRemoval removal = new RecentRemoval(key, this.nakedPutInvalidationPeriod);
recentRemovals.put(key, removal.timestamp);
// Don't let recentRemovals map become a memory leak
RecentRemoval toClean = null;
boolean attemptClean = removal.timestamp > earliestRemovalTimestamp;
removalsLock.lock();
try {
removalsQueue.add(removal);
if (attemptClean) {
if (removalsQueue.size() > 1) { // we have at least one as we
// just added it
toClean = removalsQueue.remove(0);
}
earliestRemovalTimestamp = removalsQueue.get( 0 ).timestamp;
}
} finally {
removalsLock.unlock();
}
if (toClean != null) {
Long cleaned = recentRemovals.get(toClean.key);
if (cleaned != null && cleaned.equals(toClean.timestamp)) {
cleaned = recentRemovals.remove(toClean.key);
if (cleaned != null && !cleaned.equals(toClean.timestamp)) {
// Oops; removed the wrong timestamp; restore it
recentRemovals.putIfAbsent(toClean.key, cleaned);
}
}
}
return success;
}
/**
* Invalidates all {@link #registerPendingPut(Object) previously registered pending puts} ensuring a subsequent call to
* {@link #acquirePutFromLoadLock(Object)} will return false. This method will block until any
* concurrent thread that has {@link #acquirePutFromLoadLock(Object) acquired the putFromLoad lock} for the any key has
* released the lock. This allows the caller to be certain the putFromLoad will not execute after this method returns,
* possibly caching stale data.
*
* @return true if the invalidation was successful; false if a problem occured (which the
* caller should treat as an exception condition)
*/
public boolean invalidateRegion() {
boolean ok = false;
invalidationTimestamp = System.currentTimeMillis() + this.nakedPutInvalidationPeriod;
try {
// Acquire the lock for each entry to ensure any ongoing
// work associated with it is completed before we return
for (PendingPutMap entry : pendingPuts.values()) {
if (entry.acquireLock(60, TimeUnit.SECONDS)) {
try {
entry.invalidate();
}
finally {
entry.releaseLock();
}
} else {
ok = false;
}
}
removalsLock.lock();
try {
recentRemovals.clear();
removalsQueue.clear();
ok = true;
} finally {
removalsLock.unlock();
}
}
catch (Exception e) {
ok = false;
}
finally {
earliestRemovalTimestamp = invalidationTimestamp;
}
return ok;
}
/**
* Notifies this validator that it is expected that a database read followed by a subsequent {@link
* #acquirePutFromLoadLock(Object)} call will occur. The intent is this method would be called following a cache miss
* wherein it is expected that a database read plus cache put will occur. Calling this method allows the validator to
* treat the subsequent acquirePutFromLoadLock as if the database read occurred when this method was
* invoked. This allows the validator to compare the timestamp of this call against the timestamp of subsequent removal
* notifications. A put that occurs without this call preceding it is "naked"; i.e the validator must assume the put is
* not valid if any relevant removal has occurred within {@link #NAKED_PUT_INVALIDATION_PERIOD} milliseconds.
*
* @param key key that will be used for subsequent cache put
*/
public void registerPendingPut(Object key) {
PendingPut pendingPut = new PendingPut(getOwnerForPut());
PendingPutMap pendingForKey = new PendingPutMap(pendingPut);
for (;;) {
PendingPutMap existing = pendingPuts.putIfAbsent(key, pendingForKey);
if (existing != null) {
if (existing.acquireLock(10, TimeUnit.SECONDS)) {
try {
existing.put(pendingPut);
PendingPutMap doublecheck = pendingPuts.putIfAbsent(key, existing);
if (doublecheck == null || doublecheck == existing) {
break;
}
// else we hit a race and need to loop to try again
}
finally {
existing.releaseLock();
}
} else {
// Can't get the lock; when we come back we'll be a "naked put"
break;
}
} else {
// normal case
break;
}
}
}
// -------------------------------------------------------------- Protected
/** Only for use by unit tests; may be removed at any time */
protected int getRemovalQueueLength() {
removalsLock.lock();
try {
return removalsQueue.size();
} finally {
removalsLock.unlock();
}
}
// ---------------------------------------------------------------- Private
private Object getOwnerForPut() {
Transaction tx = null;
try {
if (transactionManager != null) {
tx = transactionManager.getTransaction();
}
} catch (SystemException se) {
throw new CacheException("Could not obtain transaction", se);
}
return tx == null ? Thread.currentThread() : tx;
}
/**
* Lazy-initialization map for PendingPut. Optimized for the expected usual case where only a
* single put is pending for a given key.
*
* This class is NOT THREAD SAFE. All operations on it must be performed with the lock held.
*/
private static class PendingPutMap {
private PendingPut singlePendingPut;
private Map fullMap;
private final Lock lock = new ReentrantLock();
PendingPutMap(PendingPut singleItem) {
this.singlePendingPut = singleItem;
}
public void put(PendingPut pendingPut) {
if (singlePendingPut == null) {
if (fullMap == null) {
// initial put
singlePendingPut = pendingPut;
} else {
fullMap.put(pendingPut.owner, pendingPut);
}
} else {
// 2nd put; need a map
fullMap = new HashMap(4);
fullMap.put(singlePendingPut.owner, singlePendingPut);
singlePendingPut = null;
fullMap.put(pendingPut.owner, pendingPut);
}
}
public PendingPut remove(Object ownerForPut) {
PendingPut removed = null;
if (fullMap == null) {
if (singlePendingPut != null
&& singlePendingPut.owner.equals(ownerForPut)) {
removed = singlePendingPut;
singlePendingPut = null;
}
} else {
removed = fullMap.remove(ownerForPut);
}
return removed;
}
public int size() {
return fullMap == null ? (singlePendingPut == null ? 0 : 1)
: fullMap.size();
}
public boolean acquireLock(long time, TimeUnit unit) {
try {
return lock.tryLock(time, unit);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
return false;
}
}
public void releaseLock() {
lock.unlock();
}
public void invalidate() {
if (singlePendingPut != null) {
singlePendingPut.completed = true;
// Nullify to avoid leaking completed pending puts
singlePendingPut = null;
} else if (fullMap != null) {
for (PendingPut pp : fullMap.values()) {
pp.completed = true;
}
// Nullify to avoid leaking completed pending puts
fullMap = null;
}
}
}
private static class PendingPut {
private final Object owner;
private volatile boolean completed;
private PendingPut(Object owner) {
this.owner = owner;
}
}
private static class RecentRemoval {
private final Object key;
private final Long timestamp;
private RecentRemoval(Object key, long nakedPutInvalidationPeriod) {
this.key = key;
timestamp = System.currentTimeMillis() + nakedPutInvalidationPeriod;
}
}
}
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