2 * Copyright (c) 2016 Cisco 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.databroker.actors.dds;
10 import akka.actor.ActorRef;
11 import com.google.common.base.MoreObjects;
12 import com.google.common.base.Optional;
13 import com.google.common.base.Preconditions;
14 import com.google.common.base.Throwables;
15 import com.google.common.base.Verify;
16 import com.google.common.collect.Iterables;
17 import com.google.common.util.concurrent.CheckedFuture;
18 import com.google.common.util.concurrent.ListenableFuture;
19 import com.google.common.util.concurrent.SettableFuture;
20 import java.util.ArrayDeque;
21 import java.util.Deque;
22 import java.util.Iterator;
23 import java.util.concurrent.CountDownLatch;
24 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
25 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
26 import java.util.function.Consumer;
27 import javax.annotation.Nonnull;
28 import javax.annotation.Nullable;
29 import javax.annotation.concurrent.GuardedBy;
30 import javax.annotation.concurrent.NotThreadSafe;
31 import org.opendaylight.controller.cluster.access.client.ConnectionEntry;
32 import org.opendaylight.controller.cluster.access.commands.AbstractLocalTransactionRequest;
33 import org.opendaylight.controller.cluster.access.commands.TransactionAbortRequest;
34 import org.opendaylight.controller.cluster.access.commands.TransactionAbortSuccess;
35 import org.opendaylight.controller.cluster.access.commands.TransactionCanCommitSuccess;
36 import org.opendaylight.controller.cluster.access.commands.TransactionCommitSuccess;
37 import org.opendaylight.controller.cluster.access.commands.TransactionDoCommitRequest;
38 import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitRequest;
39 import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitSuccess;
40 import org.opendaylight.controller.cluster.access.commands.TransactionPurgeRequest;
41 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
42 import org.opendaylight.controller.cluster.access.concepts.Request;
43 import org.opendaylight.controller.cluster.access.concepts.RequestFailure;
44 import org.opendaylight.controller.cluster.access.concepts.Response;
45 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
46 import org.opendaylight.mdsal.common.api.ReadFailedException;
47 import org.opendaylight.yangtools.concepts.Identifiable;
48 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
49 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
50 import org.slf4j.Logger;
51 import org.slf4j.LoggerFactory;
54 * Class translating transaction operations towards a particular backend shard.
57 * This class is not safe to access from multiple application threads, as is usual for transactions. Internal state
58 * transitions coming from interactions with backend are expected to be thread-safe.
61 * This class interacts with the queueing mechanism in ClientActorBehavior, hence once we arrive at a decision
62 * to use either a local or remote implementation, we are stuck with it. We can re-evaluate on the next transaction.
64 * @author Robert Varga
66 abstract class AbstractProxyTransaction implements Identifiable<TransactionIdentifier> {
68 * Marker object used instead of read-type of requests, which are satisfied only once. This has a lower footprint
69 * and allows compressing multiple requests into a single entry.
72 private static final class IncrementSequence {
73 private long delta = 1;
79 void incrementDelta() {
84 // Generic state base class. Direct instances are used for fast paths, sub-class is used for successor transitions
85 private static class State {
86 private final String string;
88 State(final String string) {
89 this.string = Preconditions.checkNotNull(string);
93 public final String toString() {
98 // State class used when a successor has interfered. Contains coordinator latch, the successor and previous state
99 private static final class SuccessorState extends State {
100 private final CountDownLatch latch = new CountDownLatch(1);
101 private AbstractProxyTransaction successor;
102 private State prevState;
108 // Synchronize with succession process and return the successor
109 AbstractProxyTransaction await() {
112 } catch (InterruptedException e) {
113 LOG.warn("Interrupted while waiting for latch of {}", successor);
114 throw Throwables.propagate(e);
123 State getPrevState() {
127 void setPrevState(final State prevState) {
128 Verify.verify(this.prevState == null);
129 this.prevState = Preconditions.checkNotNull(prevState);
132 // To be called from safe contexts, where successor is known to be completed
133 AbstractProxyTransaction getSuccessor() {
134 return Verify.verifyNotNull(successor);
137 void setSuccessor(final AbstractProxyTransaction successor) {
138 Verify.verify(this.successor == null);
139 this.successor = Preconditions.checkNotNull(successor);
143 private static final Logger LOG = LoggerFactory.getLogger(AbstractProxyTransaction.class);
144 private static final AtomicIntegerFieldUpdater<AbstractProxyTransaction> SEALED_UPDATER =
145 AtomicIntegerFieldUpdater.newUpdater(AbstractProxyTransaction.class, "sealed");
146 private static final AtomicReferenceFieldUpdater<AbstractProxyTransaction, State> STATE_UPDATER =
147 AtomicReferenceFieldUpdater.newUpdater(AbstractProxyTransaction.class, State.class, "state");
148 private static final State OPEN = new State("open");
149 private static final State SEALED = new State("sealed");
150 private static final State FLUSHED = new State("flushed");
152 // Touched from client actor thread only
153 private final Deque<Object> successfulRequests = new ArrayDeque<>();
154 private final ProxyHistory parent;
156 // Accessed from user thread only, which may not access this object concurrently
157 private long sequence;
160 * Atomic state-keeping is required to synchronize the process of propagating completed transaction state towards
161 * the backend -- which may include a successor.
163 * Successor, unlike {@link AbstractProxyTransaction#seal()} is triggered from the client actor thread, which means
164 * the successor placement needs to be atomic with regard to the application thread.
166 * In the common case, the application thread performs performs the seal operations and then "immediately" sends
167 * the corresponding message. The uncommon case is when the seal and send operations race with a connect completion
168 * or timeout, when a successor is injected.
170 * This leaves the problem of needing to completely transferring state just after all queued messages are replayed
171 * after a successor was injected, so that it can be properly sealed if we are racing. Further complication comes
172 * from lock ordering, where the successor injection works with a locked queue and locks proxy objects -- leading
173 * to a potential AB-BA deadlock in case of a naive implementation.
175 * For tracking user-visible state we use a single volatile int, which is flipped atomically from 0 to 1 exactly
176 * once in {@link AbstractProxyTransaction#seal()}. That keeps common operations fast, as they need to perform
177 * only a single volatile read to assert state correctness.
179 * For synchronizing client actor (successor-injecting) and user (commit-driving) thread, we keep a separate state
180 * variable. It uses pre-allocated objects for fast paths (i.e. no successor present) and a per-transition object
181 * for slow paths (when successor is injected/present).
183 private volatile int sealed = 0;
184 private volatile State state = OPEN;
186 AbstractProxyTransaction(final ProxyHistory parent) {
187 this.parent = Preconditions.checkNotNull(parent);
190 final ActorRef localActor() {
191 return parent.localActor();
194 private void incrementSequence(final long delta) {
196 LOG.debug("Transaction {} incremented sequence to {}", this, sequence);
199 final long nextSequence() {
200 final long ret = sequence++;
201 LOG.debug("Transaction {} allocated sequence {}", this, ret);
205 final void delete(final YangInstanceIdentifier path) {
211 final void merge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
217 final void write(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
223 final CheckedFuture<Boolean, ReadFailedException> exists(final YangInstanceIdentifier path) {
225 return doExists(path);
228 final CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(final YangInstanceIdentifier path) {
233 final void enqueueRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback,
234 final long enqueuedTicks) {
235 LOG.debug("Transaction proxy {} enqueing request {} callback {}", this, request, callback);
236 parent.enqueueRequest(request, callback, enqueuedTicks);
239 final void sendRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
240 LOG.debug("Transaction proxy {} sending request {} callback {}", this, request, callback);
241 parent.sendRequest(request, callback);
245 * Seal this transaction before it is either committed or aborted.
248 // Transition user-visible state first
249 final boolean success = SEALED_UPDATER.compareAndSet(this, 0, 1);
250 Preconditions.checkState(success, "Proxy %s was already sealed", getIdentifier());
254 final void ensureSealed() {
255 if (SEALED_UPDATER.compareAndSet(this, 0, 1)) {
260 private void internalSeal() {
262 parent.onTransactionSealed(this);
264 // Now deal with state transfer, which can occur via successor or a follow-up canCommit() or directCommit().
265 if (!STATE_UPDATER.compareAndSet(this, OPEN, SEALED)) {
266 // Slow path: wait for the successor to complete
267 final AbstractProxyTransaction successor = awaitSuccessor();
269 // At this point the successor has completed transition and is possibly visible by the user thread, which is
270 // still stuck here. The successor has not seen final part of our state, nor the fact it is sealed.
271 // Propagate state and seal the successor.
272 flushState(successor);
273 successor.ensureSealed();
277 private void checkNotSealed() {
278 Preconditions.checkState(sealed == 0, "Transaction %s has already been sealed", getIdentifier());
281 private void checkSealed() {
282 Preconditions.checkState(sealed != 0, "Transaction %s has not been sealed yet", getIdentifier());
285 private SuccessorState getSuccessorState() {
286 final State local = state;
287 Verify.verify(local instanceof SuccessorState, "State %s has unexpected class", local);
288 return (SuccessorState) local;
291 private void checkReadWrite() {
292 if (isSnapshotOnly()) {
293 throw new UnsupportedOperationException("Transaction " + getIdentifier() + " is a read-only snapshot");
297 final void recordSuccessfulRequest(final @Nonnull TransactionRequest<?> req) {
298 successfulRequests.add(Verify.verifyNotNull(req));
301 final void recordFinishedRequest() {
302 final Object last = successfulRequests.peekLast();
303 if (last instanceof IncrementSequence) {
304 ((IncrementSequence) last).incrementDelta();
306 successfulRequests.addLast(new IncrementSequence());
311 * Abort this transaction. This is invoked only for read-only transactions and will result in an explicit message
312 * being sent to the backend.
317 parent.abortTransaction(this);
320 final void abort(final VotingFuture<Void> ret) {
324 if (t instanceof TransactionAbortSuccess) {
326 } else if (t instanceof RequestFailure) {
327 ret.voteNo(((RequestFailure<?, ?>) t).getCause().unwrap());
329 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
332 // This is a terminal request, hence we do not need to record it
333 LOG.debug("Transaction {} abort completed", this);
338 final void enqueueAbort(final Consumer<Response<?, ?>> callback, final long enqueuedTicks) {
339 enqueueRequest(new TransactionAbortRequest(getIdentifier(), nextSequence(), localActor()), callback,
343 final void sendAbort(final Consumer<Response<?, ?>> callback) {
344 sendRequest(new TransactionAbortRequest(getIdentifier(), nextSequence(), localActor()), callback);
348 * Commit this transaction, possibly in a coordinated fashion.
350 * @param coordinated True if this transaction should be coordinated across multiple participants.
351 * @return Future completion
353 final ListenableFuture<Boolean> directCommit() {
357 // Precludes startReconnect() from interfering with the fast path
358 synchronized (this) {
359 if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
360 final SettableFuture<Boolean> ret = SettableFuture.create();
361 sendRequest(Verify.verifyNotNull(commitRequest(false)), t -> {
362 if (t instanceof TransactionCommitSuccess) {
363 ret.set(Boolean.TRUE);
364 } else if (t instanceof RequestFailure) {
365 ret.setException(((RequestFailure<?, ?>) t).getCause().unwrap());
367 ret.setException(new IllegalStateException("Unhandled response " + t.getClass()));
370 // This is a terminal request, hence we do not need to record it
371 LOG.debug("Transaction {} directCommit completed", this);
379 // We have had some interference with successor injection, wait for it to complete and defer to the successor.
380 return awaitSuccessor().directCommit();
383 final void canCommit(final VotingFuture<?> ret) {
387 // Precludes startReconnect() from interfering with the fast path
388 synchronized (this) {
389 if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
390 final TransactionRequest<?> req = Verify.verifyNotNull(commitRequest(true));
392 sendRequest(req, t -> {
393 if (t instanceof TransactionCanCommitSuccess) {
395 } else if (t instanceof RequestFailure) {
396 ret.voteNo(((RequestFailure<?, ?>) t).getCause().unwrap());
398 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
401 recordSuccessfulRequest(req);
402 LOG.debug("Transaction {} canCommit completed", this);
409 // We have had some interference with successor injection, wait for it to complete and defer to the successor.
410 awaitSuccessor().canCommit(ret);
413 private AbstractProxyTransaction awaitSuccessor() {
414 return getSuccessorState().await();
417 final void preCommit(final VotingFuture<?> ret) {
421 final TransactionRequest<?> req = new TransactionPreCommitRequest(getIdentifier(), nextSequence(),
423 sendRequest(req, t -> {
424 if (t instanceof TransactionPreCommitSuccess) {
426 } else if (t instanceof RequestFailure) {
427 ret.voteNo(((RequestFailure<?, ?>) t).getCause().unwrap());
429 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
432 onPreCommitComplete(req);
436 private void onPreCommitComplete(final TransactionRequest<?> req) {
438 * The backend has agreed that the transaction has entered PRE_COMMIT phase, meaning it will be committed
439 * to storage after the timeout completes.
441 * All state has been replicated to the backend, hence we do not need to keep it around. Retain only
442 * the precommit request, so we know which request to use for resync.
444 LOG.debug("Transaction {} preCommit completed, clearing successfulRequests", this);
445 successfulRequests.clear();
447 // TODO: this works, but can contain some useless state (like batched operations). Create an empty
448 // equivalent of this request and store that.
449 recordSuccessfulRequest(req);
452 final void doCommit(final VotingFuture<?> ret) {
456 sendRequest(new TransactionDoCommitRequest(getIdentifier(), nextSequence(), localActor()), t -> {
457 if (t instanceof TransactionCommitSuccess) {
459 } else if (t instanceof RequestFailure) {
460 ret.voteNo(((RequestFailure<?, ?>) t).getCause().unwrap());
462 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
465 LOG.debug("Transaction {} doCommit completed", this);
470 final void sendPurge() {
471 successfulRequests.clear();
473 final TransactionRequest<?> req = new TransactionPurgeRequest(getIdentifier(), nextSequence(), localActor());
474 sendRequest(req, t -> {
475 LOG.debug("Transaction {} purge completed", this);
476 parent.completeTransaction(this);
480 final void enqueuePurge(final long enqueuedTicks) {
481 successfulRequests.clear();
483 final TransactionRequest<?> req = new TransactionPurgeRequest(getIdentifier(), nextSequence(), localActor());
484 enqueueRequest(req, t -> {
485 LOG.debug("Transaction {} purge completed", this);
486 parent.completeTransaction(this);
490 // Called with the connection unlocked
491 final synchronized void startReconnect() {
492 // At this point canCommit/directCommit are blocked, we assert a new successor state, retrieving the previous
493 // state. This method is called with the queue still unlocked.
494 final SuccessorState nextState = new SuccessorState();
495 final State prevState = STATE_UPDATER.getAndSet(this, nextState);
497 LOG.debug("Start reconnect of proxy {} previous state {}", this, prevState);
498 Verify.verify(!(prevState instanceof SuccessorState), "Proxy %s duplicate reconnect attempt after %s", this,
501 // We have asserted a slow-path state, seal(), canCommit(), directCommit() are forced to slow paths, which will
502 // wait until we unblock nextState's latch before accessing state. Now we record prevState for later use and we
504 nextState.setPrevState(prevState);
507 // Called with the connection locked
508 final void replayMessages(final AbstractProxyTransaction successor,
509 final Iterable<ConnectionEntry> enqueuedEntries) {
510 final SuccessorState local = getSuccessorState();
511 local.setSuccessor(successor);
513 // Replay successful requests first
514 if (!successfulRequests.isEmpty()) {
515 // We need to find a good timestamp to use for successful requests, as we do not want to time them out
516 // nor create timing inconsistencies in the queue -- requests are expected to be ordered by their enqueue
517 // time. We will pick the time of the first entry available. If there is none, we will just use current
518 // time, as all other requests will get enqueued afterwards.
519 final ConnectionEntry firstInQueue = Iterables.getFirst(enqueuedEntries, null);
520 final long now = firstInQueue != null ? firstInQueue.getEnqueuedTicks() : parent.currentTime();
522 for (Object obj : successfulRequests) {
523 if (obj instanceof TransactionRequest) {
524 LOG.debug("Forwarding successful request {} to successor {}", obj, successor);
525 successor.replayRequest((TransactionRequest<?>) obj, resp -> { }, now);
527 Verify.verify(obj instanceof IncrementSequence);
528 successor.incrementSequence(((IncrementSequence) obj).getDelta());
531 LOG.debug("{} replayed {} successful requests", getIdentifier(), successfulRequests.size());
532 successfulRequests.clear();
535 // Now replay whatever is in the connection
536 final Iterator<ConnectionEntry> it = enqueuedEntries.iterator();
537 while (it.hasNext()) {
538 final ConnectionEntry e = it.next();
539 final Request<?, ?> req = e.getRequest();
541 if (getIdentifier().equals(req.getTarget())) {
542 Verify.verify(req instanceof TransactionRequest, "Unhandled request %s", req);
543 LOG.debug("Replaying queued request {} to successor {}", req, successor);
544 successor.replayRequest((TransactionRequest<?>) req, e.getCallback(), e.getEnqueuedTicks());
550 * Check the state at which we have started the reconnect attempt. State transitions triggered while we were
551 * reconnecting have been forced to slow paths, which will be unlocked once we unblock the state latch
552 * at the end of this method.
554 final State prevState = local.getPrevState();
555 if (SEALED.equals(prevState)) {
556 LOG.debug("Proxy {} reconnected while being sealed, propagating state to successor {}", this, successor);
557 flushState(successor);
558 successor.ensureSealed();
563 * Invoked from {@link #replayMessages(AbstractProxyTransaction, Iterable)} to have successor adopt an in-flight
567 * Note: this method is invoked by the predecessor on the successor.
569 * @param request Request which needs to be forwarded
570 * @param callback Callback to be invoked once the request completes
571 * @param enqueuedTicks ticker-based time stamp when the request was enqueued
573 private void replayRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback,
574 final long enqueuedTicks) {
575 if (request instanceof AbstractLocalTransactionRequest) {
576 handleReplayedLocalRequest((AbstractLocalTransactionRequest<?>) request, callback, enqueuedTicks);
578 handleReplayedRemoteRequest(request, callback, enqueuedTicks);
582 // Called with the connection locked
583 final void finishReconnect() {
584 final SuccessorState local = getSuccessorState();
585 LOG.debug("Finishing reconnect of proxy {}", this);
587 // All done, release the latch, unblocking seal() and canCommit() slow paths
592 * Invoked from a retired connection for requests which have been in-flight and need to be re-adjusted
593 * and forwarded to the successor connection.
595 * @param request Request to be forwarded
596 * @param callback Original callback
598 final void forwardRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
599 forwardToSuccessor(getSuccessorState().getSuccessor(), request, callback);
602 final void forwardToSuccessor(final AbstractProxyTransaction successor, final TransactionRequest<?> request,
603 final Consumer<Response<?, ?>> callback) {
604 if (successor instanceof LocalProxyTransaction) {
605 forwardToLocal((LocalProxyTransaction)successor, request, callback);
606 } else if (successor instanceof RemoteProxyTransaction) {
607 forwardToRemote((RemoteProxyTransaction)successor, request, callback);
609 throw new IllegalStateException("Unhandled successor " + successor);
613 abstract boolean isSnapshotOnly();
615 abstract void doDelete(YangInstanceIdentifier path);
617 abstract void doMerge(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
619 abstract void doWrite(YangInstanceIdentifier path, NormalizedNode<?, ?> data);
621 abstract CheckedFuture<Boolean, ReadFailedException> doExists(YangInstanceIdentifier path);
623 abstract CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> doRead(YangInstanceIdentifier path);
625 abstract void doSeal();
627 abstract void doAbort();
630 abstract void flushState(AbstractProxyTransaction successor);
632 abstract TransactionRequest<?> commitRequest(boolean coordinated);
635 * Replay a request originating in this proxy to a successor remote proxy.
637 abstract void forwardToRemote(RemoteProxyTransaction successor, TransactionRequest<?> request,
638 Consumer<Response<?, ?>> callback);
641 * Replay a request originating in this proxy to a successor local proxy.
643 abstract void forwardToLocal(LocalProxyTransaction successor, TransactionRequest<?> request,
644 Consumer<Response<?, ?>> callback);
647 * Invoked from {@link LocalProxyTransaction} when it replays its successful requests to its successor.
650 * Note: this method is invoked by the predecessor on the successor.
652 * @param request Request which needs to be forwarded
653 * @param callback Callback to be invoked once the request completes
654 * @param enqueuedTicks Time stamp to use for enqueue time
656 abstract void handleReplayedLocalRequest(AbstractLocalTransactionRequest<?> request,
657 @Nullable Consumer<Response<?, ?>> callback, long enqueuedTicks);
660 * Invoked from {@link RemoteProxyTransaction} when it replays its successful requests to its successor.
663 * Note: this method is invoked by the predecessor on the successor.
665 * @param request Request which needs to be forwarded
666 * @param callback Callback to be invoked once the request completes
667 * @param enqueuedTicks Time stamp to use for enqueue time
669 abstract void handleReplayedRemoteRequest(TransactionRequest<?> request,
670 @Nullable Consumer<Response<?, ?>> callback, long enqueuedTicks);
673 public final String toString() {
674 return MoreObjects.toStringHelper(this).add("identifier", getIdentifier()).add("state", state).toString();