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* Copyright 2011 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,
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
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package org.infinispan.interceptors.locking;
import org.infinispan.commands.read.GetKeyValueCommand;
import org.infinispan.commands.tx.CommitCommand;
import org.infinispan.commands.tx.PrepareCommand;
import org.infinispan.commands.tx.RollbackCommand;
import org.infinispan.commands.write.EvictCommand;
import org.infinispan.configuration.cache.Configurations;
import org.infinispan.context.Flag;
import org.infinispan.context.InvocationContext;
import org.infinispan.context.impl.TxInvocationContext;
import org.infinispan.factories.annotations.Inject;
import org.infinispan.remoting.rpc.RpcManager;
import org.infinispan.transaction.LocalTransaction;
import org.infinispan.transaction.TransactionTable;
import org.infinispan.transaction.xa.CacheTransaction;
import org.infinispan.transaction.xa.GlobalTransaction;
import org.infinispan.util.concurrent.TimeoutException;
import org.infinispan.util.logging.Log;
import java.util.Collection;
import static org.infinispan.util.Util.toStr;
/**
* Base class for transaction based locking interceptors.
*
* @author Mircea.Markus@jboss.com
* @since 5.1
*/
public abstract class AbstractTxLockingInterceptor extends AbstractLockingInterceptor {
protected TransactionTable txTable;
protected RpcManager rpcManager;
private boolean clustered;
@Inject
@SuppressWarnings("unused")
public void setDependencies(TransactionTable txTable, RpcManager rpcManager) {
this.txTable = txTable;
this.rpcManager = rpcManager;
clustered = rpcManager != null;
}
@Override
public Object visitRollbackCommand(TxInvocationContext ctx, RollbackCommand command) throws Throwable {
try {
return invokeNextInterceptor(ctx, command);
} finally {
lockManager.unlockAll(ctx);
}
}
@Override
public final Object visitEvictCommand(InvocationContext ctx, EvictCommand command) throws Throwable {
// ensure keys are properly locked for evict commands
command.setFlags(Flag.ZERO_LOCK_ACQUISITION_TIMEOUT, Flag.CACHE_MODE_LOCAL);
try {
lockKey(ctx, command.getKey(), 0, command.hasFlag(Flag.SKIP_LOCKING));
return invokeNextInterceptor(ctx, command);
} finally {
//evict doesn't get called within a tx scope, so we should apply the changes before returning
lockManager.unlockAll(ctx);
}
}
@Override
public Object visitGetKeyValueCommand(InvocationContext ctx, GetKeyValueCommand command) throws Throwable {
try {
return super.visitGetKeyValueCommand(ctx, command);
} finally {
//when not invoked in an explicit tx's scope the get is non-transactional(mainly for efficiency).
//locks need to be released in this situation as they might have been acquired from L1.
if (!ctx.isInTxScope()) lockManager.unlockAll(ctx);
}
}
@Override
public Object visitCommitCommand(TxInvocationContext ctx, CommitCommand command) throws Throwable {
try {
return super.visitCommitCommand(ctx, command);
} finally {
if (releaseLockOnTxCompletion(ctx)) lockManager.unlockAll(ctx);
}
}
protected final Object invokeNextAndCommitIf1Pc(TxInvocationContext ctx, PrepareCommand command) throws Throwable {
Object result = invokeNextInterceptor(ctx, command);
if (command.isOnePhaseCommit() && releaseLockOnTxCompletion(ctx)) {
lockManager.unlockAll(ctx);
}
return result;
}
/**
* The backup (non-primary) owners keep a "backup lock" for each key they received in a lock/prepare command.
* Normally there can be many transactions holding the backup lock at the same time, but when the secondary owner
* becomes a primary owner a new transaction trying to obtain the "real" lock will have to wait for all backup
* locks to be released. The backup lock will be released either by a commit/rollback/unlock command or by
* the originator leaving the cluster (if recovery is disabled).
*/
protected final void lockAndRegisterBackupLock(TxInvocationContext ctx, Object key, long lockTimeout, boolean skipLocking) throws InterruptedException {
if (cdl.localNodeIsPrimaryOwner(key)) {
lockKeyAndCheckOwnership(ctx, key, lockTimeout, skipLocking);
} else if (cdl.localNodeIsOwner(key)) {
ctx.getCacheTransaction().addBackupLockForKey(key);
}
}
/**
* Besides acquiring a lock, this method also handles the following situation:
* 1. consistentHash("k") == {A, B}, tx1 prepared on A and B. Then node A crashed (A == single lock owner)
* 2. at this point tx2 which also writes "k" tries to prepare on B.
* 3. tx2 has to determine that "k" is already locked by another tx (i.e. tx1) and it has to wait for that tx to finish before acquiring the lock.
*
* The algorithm used at step 3 is:
* - the transaction table(TT) associates the current topology id with every remote and local transaction it creates
* - TT also keeps track of the minimal value of all the topology ids of all the transactions still present in the cache (minTopologyId)
* - when a tx wants to acquire lock "k":
* - if tx.topologyId > TT.minTopologyId then "k" might be a key whose owner crashed. If so:
* - obtain the list LT of transactions that started in a previous topology (txTable.getTransactionsPreparedBefore)
* - for each t in LT:
* - if t wants to write "k" then block until t finishes (CacheTransaction.waitForTransactionsToFinishIfItWritesToKey)
* - only then try to acquire lock on "k"
* - if tx.topologyId == TT.minTopologyId try to acquire lock straight away.
*
* Note: The algorithm described below only when nodes leave the cluster, so it doesn't add a performance burden
* when the cluster is stable.
*/
protected final void lockKeyAndCheckOwnership(InvocationContext ctx, Object key, long lockTimeout, boolean skipLocking) throws InterruptedException {
TxInvocationContext txContext = (TxInvocationContext) ctx;
int transactionTopologyId = -1;
boolean checkForPendingLocks = false;
if (clustered) {
CacheTransaction tx = txContext.getCacheTransaction();
boolean isFromStateTransfer = txContext.isOriginLocal() && ((LocalTransaction)tx).isFromStateTransfer();
// if the transaction is from state transfer it should not wait for the backup locks of other transactions
if (!isFromStateTransfer) {
transactionTopologyId = tx.getTopologyId();
if (transactionTopologyId != TransactionTable.CACHE_STOPPED_TOPOLOGY_ID) {
checkForPendingLocks = txTable.getMinTopologyId() < transactionTopologyId;
}
}
}
Log log = getLog();
boolean trace = log.isTraceEnabled();
if (checkForPendingLocks) {
if (trace)
log.tracef("Checking for pending locks and then locking key %s", toStr(key));
final long expectedEndTime = nowMillis() + cacheConfiguration.locking().lockAcquisitionTimeout();
// Check local transactions first
waitForTransactionsToComplete(txContext, txTable.getLocalTransactions(), key, transactionTopologyId, expectedEndTime);
// ... then remote ones
waitForTransactionsToComplete(txContext, txTable.getRemoteTransactions(), key, transactionTopologyId, expectedEndTime);
// Then try to acquire a lock
final long remaining = expectedEndTime - nowMillis();
if (remaining <= 0) {
throw newTimeoutException(key, txContext);
} else {
if (trace)
log.tracef("Finished waiting for other potential lockers, trying to acquire the lock on %s", toStr(key));
lockManager.acquireLock(ctx, key, remaining, skipLocking);
}
} else {
if (trace)
log.tracef("Locking key %s, no need to check for pending locks.", toStr(key));
lockManager.acquireLock(ctx, key, lockTimeout, skipLocking);
}
}
private void waitForTransactionsToComplete(TxInvocationContext txContext, Collection<? extends CacheTransaction> transactions,
Object key, int transactionTopologyId, long expectedEndTime) throws InterruptedException {
GlobalTransaction thisTransaction = txContext.getGlobalTransaction();
for (CacheTransaction tx : transactions) {
if (tx.getTopologyId() < transactionTopologyId) {
// don't wait for the current transaction
if (tx.getGlobalTransaction().equals(thisTransaction))
continue;
boolean txCompleted = false;
long remaining;
while ((remaining = expectedEndTime - nowMillis()) > 0) {
if (tx.waitForLockRelease(key, remaining)) {
txCompleted = true;
break;
}
}
if (!txCompleted) {
throw newTimeoutException(key, txContext);
}
}
}
}
private TimeoutException newTimeoutException(Object key, TxInvocationContext txContext) {
return new TimeoutException("Could not acquire lock on " + key + " on behalf of transaction " +
txContext.getGlobalTransaction() + ". Lock is being held by " + lockManager.getOwner(key));
}
private boolean releaseLockOnTxCompletion(TxInvocationContext ctx) {
return ctx.isOriginLocal() || Configurations.isSecondPhaseAsync(cacheConfiguration);
}
private long nowMillis() {
//use nanos as is more precise and less expensive.
return System.nanoTime() / 1000000;
}
}