2 * Copyright (c) 2015 Brocade Communications Systems, Inc. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.controller.cluster.datastore;
10 import akka.actor.ActorSelection;
11 import akka.dispatch.Futures;
12 import com.google.common.base.Preconditions;
13 import java.util.AbstractMap.SimpleImmutableEntry;
14 import java.util.ArrayList;
15 import java.util.Collection;
16 import java.util.List;
17 import java.util.Map.Entry;
18 import java.util.Optional;
19 import java.util.SortedSet;
20 import java.util.concurrent.TimeUnit;
21 import javax.annotation.concurrent.GuardedBy;
22 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
23 import org.opendaylight.controller.cluster.datastore.utils.ActorContext;
24 import org.slf4j.Logger;
25 import org.slf4j.LoggerFactory;
26 import scala.concurrent.Future;
27 import scala.concurrent.Promise;
30 * A helper class that wraps an eventual TransactionContext instance. Operations destined for the target
31 * TransactionContext instance are cached until the TransactionContext instance becomes available at which
32 * time they are executed.
34 * @author Thomas Pantelis
36 class TransactionContextWrapper {
37 private static final Logger LOG = LoggerFactory.getLogger(TransactionContextWrapper.class);
40 * The list of transaction operations to execute once the TransactionContext becomes available.
42 @GuardedBy("queuedTxOperations")
43 private final List<Entry<TransactionOperation, Boolean>> queuedTxOperations = new ArrayList<>();
44 private final TransactionIdentifier identifier;
45 private final OperationLimiter limiter;
46 private final String shardName;
49 * The resulting TransactionContext.
51 private volatile TransactionContext transactionContext;
52 @GuardedBy("queuedTxOperations")
53 private TransactionContext deferredTransactionContext;
54 @GuardedBy("queuedTxOperations")
55 private boolean pendingEnqueue;
57 TransactionContextWrapper(final TransactionIdentifier identifier, final ActorContext actorContext,
58 final String shardName) {
59 this.identifier = Preconditions.checkNotNull(identifier);
60 this.limiter = new OperationLimiter(identifier,
61 // 1 extra permit for the ready operation
62 actorContext.getDatastoreContext().getShardBatchedModificationCount() + 1,
63 TimeUnit.MILLISECONDS.toSeconds(actorContext.getDatastoreContext().getOperationTimeoutInMillis()));
64 this.shardName = Preconditions.checkNotNull(shardName);
67 TransactionContext getTransactionContext() {
68 return transactionContext;
71 TransactionIdentifier getIdentifier() {
76 * Adds a TransactionOperation to be executed once the TransactionContext becomes available. This method is called
77 * only after the caller has checked (without synchronizing with executePriorTransactionOperations()) that the
78 * context is not available.
80 private void enqueueTransactionOperation(final TransactionOperation operation) {
81 // We have three things to do here:
82 // - synchronize with executePriorTransactionOperations() so that logical operation ordering is maintained
83 // - acquire a permit for the operation if we still need to enqueue it
84 // - enqueue the operation
86 // Since each operation needs to acquire a permit exactly once and the limiter is shared between us and the
87 // TransactionContext, we need to know whether an operation has a permit before we enqueue it. Further
89 // - this method may be called from the thread invoking executePriorTransactionOperations()
90 // - user may be violating API contract of using the transaction from a single thread
92 // As a first step, we will synchronize on the queue and check if the handoff has completed. While we have
93 // the lock, we will assert that we will be enqueing another operation.
94 final TransactionContext contextOnEntry;
95 synchronized (queuedTxOperations) {
96 contextOnEntry = transactionContext;
97 if (contextOnEntry == null) {
98 Preconditions.checkState(pendingEnqueue == false, "Concurrent access to transaction %s detected",
100 pendingEnqueue = true;
104 // Short-circuit if there is a context
105 if (contextOnEntry != null) {
106 operation.invoke(transactionContext, null);
110 boolean cleanupEnqueue = true;
111 TransactionContext finishHandoff = null;
113 // Acquire the permit,
114 final boolean havePermit = limiter.acquire();
116 LOG.warn("Failed to acquire enqueue operation permit for transaction {} on shard {}", identifier,
120 // Ready to enqueue, take the lock again and append the operation
121 synchronized (queuedTxOperations) {
122 LOG.debug("Tx {} Queuing TransactionOperation", identifier);
123 queuedTxOperations.add(new SimpleImmutableEntry<>(operation, havePermit));
124 pendingEnqueue = false;
125 cleanupEnqueue = false;
126 finishHandoff = deferredTransactionContext;
127 deferredTransactionContext = null;
130 if (cleanupEnqueue) {
131 synchronized (queuedTxOperations) {
132 pendingEnqueue = false;
133 finishHandoff = deferredTransactionContext;
134 deferredTransactionContext = null;
137 if (finishHandoff != null) {
138 executePriorTransactionOperations(finishHandoff);
143 void maybeExecuteTransactionOperation(final TransactionOperation op) {
144 final TransactionContext localContext = transactionContext;
145 if (localContext != null) {
146 op.invoke(localContext, null);
148 // The shard Tx hasn't been created yet so add the Tx operation to the Tx Future
149 // callback to be executed after the Tx is created.
150 enqueueTransactionOperation(op);
154 void executePriorTransactionOperations(final TransactionContext localTransactionContext) {
156 // Access to queuedTxOperations and transactionContext must be protected and atomic
157 // (ie synchronized) with respect to #addTxOperationOnComplete to handle timing
158 // issues and ensure no TransactionOperation is missed and that they are processed
159 // in the order they occurred.
161 // We'll make a local copy of the queuedTxOperations list to handle re-entrancy
162 // in case a TransactionOperation results in another transaction operation being
163 // queued (eg a put operation from a client read Future callback that is notified
165 final Collection<Entry<TransactionOperation, Boolean>> operationsBatch;
166 synchronized (queuedTxOperations) {
167 if (queuedTxOperations.isEmpty()) {
168 if (!pendingEnqueue) {
169 // We're done invoking the TransactionOperations so we can now publish the TransactionContext.
170 localTransactionContext.operationHandOffComplete();
172 // This is null-to-non-null transition after which we are releasing the lock and not doing
173 // any further processing.
174 transactionContext = localTransactionContext;
176 deferredTransactionContext = localTransactionContext;
181 operationsBatch = new ArrayList<>(queuedTxOperations);
182 queuedTxOperations.clear();
185 // Invoke TransactionOperations outside the sync block to avoid unnecessary blocking. A slight down-side is
186 // that we need to re-acquire the lock below but this should be negligible.
187 for (Entry<TransactionOperation, Boolean> oper : operationsBatch) {
188 final Boolean permit = oper.getValue();
189 if (permit.booleanValue() && !localTransactionContext.usesOperationLimiting()) {
190 // If the context is not using limiting we need to release operations as we are queueing them, so
191 // user threads are not charged for them.
194 oper.getKey().invoke(localTransactionContext, permit);
199 Future<ActorSelection> readyTransaction(Optional<SortedSet<String>> participatingShardNames) {
200 // avoid the creation of a promise and a TransactionOperation
201 final TransactionContext localContext = transactionContext;
202 if (localContext != null) {
203 return localContext.readyTransaction(null, participatingShardNames);
206 final Promise<ActorSelection> promise = Futures.promise();
207 enqueueTransactionOperation(new TransactionOperation() {
209 public void invoke(final TransactionContext newTransactionContext, final Boolean havePermit) {
210 promise.completeWith(newTransactionContext.readyTransaction(havePermit, participatingShardNames));
214 return promise.future();
217 OperationLimiter getLimiter() {