opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/databroker/actors/dds/AbstractProxyTransaction.java

   1 /*
   2  * Copyright (c) 2016 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   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
   7  */
   8 package org.opendaylight.controller.cluster.databroker.actors.dds;
   9
  10 import akka.actor.ActorRef;
  11 import com.google.common.base.Optional;
  12 import com.google.common.base.Preconditions;
  13 import com.google.common.base.Throwables;
  14 import com.google.common.base.Verify;
  15 import com.google.common.util.concurrent.CheckedFuture;
  16 import com.google.common.util.concurrent.ListenableFuture;
  17 import com.google.common.util.concurrent.SettableFuture;
  18 import java.util.ArrayDeque;
  19 import java.util.Deque;
  20 import java.util.Iterator;
  21 import java.util.concurrent.CountDownLatch;
  22 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
  23 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  24 import java.util.function.Consumer;
  25 import javax.annotation.Nonnull;
  26 import javax.annotation.Nullable;
  27 import javax.annotation.concurrent.GuardedBy;
  28 import javax.annotation.concurrent.NotThreadSafe;
  29 import org.opendaylight.controller.cluster.access.client.ConnectionEntry;
  30 import org.opendaylight.controller.cluster.access.commands.TransactionAbortRequest;
  31 import org.opendaylight.controller.cluster.access.commands.TransactionAbortSuccess;
  32 import org.opendaylight.controller.cluster.access.commands.TransactionCanCommitSuccess;
  33 import org.opendaylight.controller.cluster.access.commands.TransactionCommitSuccess;
  34 import org.opendaylight.controller.cluster.access.commands.TransactionDoCommitRequest;
  35 import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitRequest;
  36 import org.opendaylight.controller.cluster.access.commands.TransactionPreCommitSuccess;
  37 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  38 import org.opendaylight.controller.cluster.access.concepts.Request;
  39 import org.opendaylight.controller.cluster.access.concepts.RequestFailure;
  40 import org.opendaylight.controller.cluster.access.concepts.Response;
  41 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  42 import org.opendaylight.mdsal.common.api.ReadFailedException;
  43 import org.opendaylight.yangtools.concepts.Identifiable;
  44 import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
  45 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
  46 import org.slf4j.Logger;
  47 import org.slf4j.LoggerFactory;
  48
  49 /**
  50  * Class translating transaction operations towards a particular backend shard.
  51  *
  52  * <p>
  53  * This class is not safe to access from multiple application threads, as is usual for transactions. Internal state
  54  * transitions coming from interactions with backend are expected to be thread-safe.
  55  *
  56  * <p>
  57  * This class interacts with the queueing mechanism in ClientActorBehavior, hence once we arrive at a decision
  58  * to use either a local or remote implementation, we are stuck with it. We can re-evaluate on the next transaction.
  59  *
  60  * @author Robert Varga
  61  */
  62 abstract class AbstractProxyTransaction implements Identifiable<TransactionIdentifier> {
  63     /**
  64      * Marker object used instead of read-type of requests, which are satisfied only once. This has a lower footprint
  65      * and allows compressing multiple requests into a single entry.
  66      */
  67     @NotThreadSafe
  68     private static final class IncrementSequence {
  69         private long delta = 1;
  70
  71         long getDelta() {
  72             return delta;
  73         }
  74
  75         void incrementDelta() {
  76             delta++;
  77         }
  78     }
  79
  80     // Generic state base class. Direct instances are used for fast paths, sub-class is used for successor transitions
  81     private static class State {
  82         private final String string;
  83
  84         State(final String string) {
  85             this.string = Preconditions.checkNotNull(string);
  86         }
  87
  88         @Override
  89         public final String toString() {
  90             return string;
  91         }
  92     }
  93
  94     // State class used when a successor has interfered. Contains coordinator latch, the successor and previous state
  95     private static final class SuccessorState extends State {
  96         private final CountDownLatch latch = new CountDownLatch(1);
  97         private AbstractProxyTransaction successor;
  98         private State prevState;
  99
 100         SuccessorState() {
 101             super("successor");
 102         }
 103
 104         // Synchronize with succession process and return the successor
 105         AbstractProxyTransaction await() {
 106             try {
 107                 latch.await();
 108             } catch (InterruptedException e) {
 109                 LOG.warn("Interrupted while waiting for latch of {}", successor);
 110                 throw Throwables.propagate(e);
 111             }
 112             return successor;
 113         }
 114
 115         void finish() {
 116             latch.countDown();
 117         }
 118
 119         State getPrevState() {
 120             return prevState;
 121         }
 122
 123         void setPrevState(final State prevState) {
 124             Verify.verify(this.prevState == null);
 125             this.prevState = Preconditions.checkNotNull(prevState);
 126         }
 127
 128         // To be called from safe contexts, where successor is known to be completed
 129         AbstractProxyTransaction getSuccessor() {
 130             return Verify.verifyNotNull(successor);
 131         }
 132
 133         void setSuccessor(final AbstractProxyTransaction successor) {
 134             Verify.verify(this.successor == null);
 135             this.successor = Preconditions.checkNotNull(successor);
 136         }
 137     }
 138
 139     private static final Logger LOG = LoggerFactory.getLogger(AbstractProxyTransaction.class);
 140     private static final AtomicIntegerFieldUpdater<AbstractProxyTransaction> SEALED_UPDATER =
 141             AtomicIntegerFieldUpdater.newUpdater(AbstractProxyTransaction.class, "sealed");
 142     private static final AtomicReferenceFieldUpdater<AbstractProxyTransaction, State> STATE_UPDATER =
 143             AtomicReferenceFieldUpdater.newUpdater(AbstractProxyTransaction.class, State.class, "state");
 144     private static final State OPEN = new State("open");
 145     private static final State SEALED = new State("sealed");
 146     private static final State FLUSHED = new State("flushed");
 147
 148     // Touched from client actor thread only
 149     private final Deque<Object> successfulRequests = new ArrayDeque<>();
 150     private final ProxyHistory parent;
 151
 152     // Accessed from user thread only, which may not access this object concurrently
 153     private long sequence;
 154
 155     /*
 156      * Atomic state-keeping is required to synchronize the process of propagating completed transaction state towards
 157      * the backend -- which may include a successor.
 158      *
 159      * Successor, unlike {@link AbstractProxyTransaction#seal()} is triggered from the client actor thread, which means
 160      * the successor placement needs to be atomic with regard to the application thread.
 161      *
 162      * In the common case, the application thread performs performs the seal operations and then "immediately" sends
 163      * the corresponding message. The uncommon case is when the seal and send operations race with a connect completion
 164      * or timeout, when a successor is injected.
 165      *
 166      * This leaves the problem of needing to completely transferring state just after all queued messages are replayed
 167      * after a successor was injected, so that it can be properly sealed if we are racing. Further complication comes
 168      * from lock ordering, where the successor injection works with a locked queue and locks proxy objects -- leading
 169      * to a potential AB-BA deadlock in case of a naive implementation.
 170      *
 171      * For tracking user-visible state we use a single volatile int, which is flipped atomically from 0 to 1 exactly
 172      * once in {@link AbstractProxyTransaction#seal()}. That keeps common operations fast, as they need to perform
 173      * only a single volatile read to assert state correctness.
 174      *
 175      * For synchronizing client actor (successor-injecting) and user (commit-driving) thread, we keep a separate state
 176      * variable. It uses pre-allocated objects for fast paths (i.e. no successor present) and a per-transition object
 177      * for slow paths (when successor is injected/present).
 178      */
 179     private volatile int sealed = 0;
 180     private volatile State state = OPEN;
 181
 182     AbstractProxyTransaction(final ProxyHistory parent) {
 183         this.parent = Preconditions.checkNotNull(parent);
 184     }
 185
 186     final ActorRef localActor() {
 187         return parent.localActor();
 188     }
 189
 190     private void incrementSequence(final long delta) {
 191         sequence += delta;
 192         LOG.debug("Transaction {} incremented sequence to {}", this, sequence);
 193     }
 194
 195     final long nextSequence() {
 196         final long ret = sequence++;
 197         LOG.debug("Transaction {} allocated sequence {}", this, ret);
 198         return ret;
 199     }
 200
 201     final void delete(final YangInstanceIdentifier path) {
 202         checkReadWrite();
 203         checkNotSealed();
 204         doDelete(path);
 205     }
 206
 207     final void merge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
 208         checkReadWrite();
 209         checkNotSealed();
 210         doMerge(path, data);
 211     }
 212
 213     final void write(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data) {
 214         checkReadWrite();
 215         checkNotSealed();
 216         doWrite(path, data);
 217     }
 218
 219     final CheckedFuture<Boolean, ReadFailedException> exists(final YangInstanceIdentifier path) {
 220         checkNotSealed();
 221         return doExists(path);
 222     }
 223
 224     final CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read(final YangInstanceIdentifier path) {
 225         checkNotSealed();
 226         return doRead(path);
 227     }
 228
 229     final void sendRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
 230         LOG.debug("Transaction proxy {} sending request {} callback {}", this, request, callback);
 231         parent.sendRequest(request, callback);
 232     }
 233
 234     /**
 235      * Seal this transaction before it is either committed or aborted.
 236      */
 237     final void seal() {
 238         // Transition user-visible state first
 239         final boolean success = SEALED_UPDATER.compareAndSet(this, 0, 1);
 240         Preconditions.checkState(success, "Proxy %s was already sealed", getIdentifier());
 241         doSeal();
 242         parent.onTransactionSealed(this);
 243
 244         // Now deal with state transfer, which can occur via successor or a follow-up canCommit() or directCommit().
 245         if (!STATE_UPDATER.compareAndSet(this, OPEN, SEALED)) {
 246             // Slow path: wait for the successor to complete
 247             final AbstractProxyTransaction successor = awaitSuccessor();
 248
 249             // At this point the successor has completed transition and is possibly visible by the user thread, which is
 250             // still stuck here. The successor has not seen final part of our state, nor the fact it is sealed.
 251             // Propagate state and seal the successor.
 252             flushState(successor);
 253             successor.seal();
 254         }
 255     }
 256
 257     private void checkNotSealed() {
 258         Preconditions.checkState(sealed == 0, "Transaction %s has already been sealed", getIdentifier());
 259     }
 260
 261     private void checkSealed() {
 262         Preconditions.checkState(sealed != 0, "Transaction %s has not been sealed yet", getIdentifier());
 263     }
 264
 265     private SuccessorState getSuccessorState() {
 266         final State local = state;
 267         Verify.verify(local instanceof SuccessorState, "State %s has unexpected class", local);
 268         return (SuccessorState) local;
 269     }
 270
 271     private void checkReadWrite() {
 272         if (isSnapshotOnly()) {
 273             throw new UnsupportedOperationException("Transaction " + getIdentifier() + " is a read-only snapshot");
 274         }
 275     }
 276
 277     final void recordSuccessfulRequest(final @Nonnull TransactionRequest<?> req) {
 278         successfulRequests.add(Verify.verifyNotNull(req));
 279     }
 280
 281     final void recordFinishedRequest() {
 282         final Object last = successfulRequests.peekLast();
 283         if (last instanceof IncrementSequence) {
 284             ((IncrementSequence) last).incrementDelta();
 285         } else {
 286             successfulRequests.addLast(new IncrementSequence());
 287         }
 288     }
 289
 290     /**
 291      * Abort this transaction. This is invoked only for read-only transactions and will result in an explicit message
 292      * being sent to the backend.
 293      */
 294     final void abort() {
 295         checkNotSealed();
 296         doAbort();
 297         parent.abortTransaction(this);
 298     }
 299
 300     final void abort(final VotingFuture<Void> ret) {
 301         checkSealed();
 302
 303         sendAbort(t -> {
 304             if (t instanceof TransactionAbortSuccess) {
 305                 ret.voteYes();
 306             } else if (t instanceof RequestFailure) {
 307                 ret.voteNo(((RequestFailure<?, ?>) t).getCause());
 308             } else {
 309                 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
 310             }
 311
 312             // This is a terminal request, hence we do not need to record it
 313             LOG.debug("Transaction {} abort completed", this);
 314             parent.completeTransaction(this);
 315         });
 316     }
 317
 318     final void sendAbort(final Consumer<Response<?, ?>> callback) {
 319         sendRequest(new TransactionAbortRequest(getIdentifier(), nextSequence(), localActor()), callback);
 320     }
 321
 322     /**
 323      * Commit this transaction, possibly in a coordinated fashion.
 324      *
 325      * @param coordinated True if this transaction should be coordinated across multiple participants.
 326      * @return Future completion
 327      */
 328     final ListenableFuture<Boolean> directCommit() {
 329         checkReadWrite();
 330         checkSealed();
 331
 332         // Precludes startReconnect() from interfering with the fast path
 333         synchronized (this) {
 334             if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
 335                 final SettableFuture<Boolean> ret = SettableFuture.create();
 336                 sendRequest(Verify.verifyNotNull(commitRequest(false)), t -> {
 337                     if (t instanceof TransactionCommitSuccess) {
 338                         ret.set(Boolean.TRUE);
 339                     } else if (t instanceof RequestFailure) {
 340                         ret.setException(((RequestFailure<?, ?>) t).getCause());
 341                     } else {
 342                         ret.setException(new IllegalStateException("Unhandled response " + t.getClass()));
 343                     }
 344
 345                     // This is a terminal request, hence we do not need to record it
 346                     LOG.debug("Transaction {} directCommit completed", this);
 347                     parent.completeTransaction(this);
 348                 });
 349
 350                 return ret;
 351             }
 352         }
 353
 354         // We have had some interference with successor injection, wait for it to complete and defer to the successor.
 355         return awaitSuccessor().directCommit();
 356     }
 357
 358     final void canCommit(final VotingFuture<?> ret) {
 359         checkReadWrite();
 360         checkSealed();
 361
 362         // Precludes startReconnect() from interfering with the fast path
 363         synchronized (this) {
 364             if (STATE_UPDATER.compareAndSet(this, SEALED, FLUSHED)) {
 365                 final TransactionRequest<?> req = Verify.verifyNotNull(commitRequest(true));
 366
 367                 sendRequest(req, t -> {
 368                     if (t instanceof TransactionCanCommitSuccess) {
 369                         ret.voteYes();
 370                     } else if (t instanceof RequestFailure) {
 371                         ret.voteNo(((RequestFailure<?, ?>) t).getCause());
 372                     } else {
 373                         ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
 374                     }
 375
 376                     recordSuccessfulRequest(req);
 377                     LOG.debug("Transaction {} canCommit completed", this);
 378                 });
 379
 380                 return;
 381             }
 382         }
 383
 384         // We have had some interference with successor injection, wait for it to complete and defer to the successor.
 385         awaitSuccessor().canCommit(ret);
 386     }
 387
 388     private AbstractProxyTransaction awaitSuccessor() {
 389         return getSuccessorState().await();
 390     }
 391
 392     final void preCommit(final VotingFuture<?> ret) {
 393         checkReadWrite();
 394         checkSealed();
 395
 396         final TransactionRequest<?> req = new TransactionPreCommitRequest(getIdentifier(), nextSequence(),
 397             localActor());
 398         sendRequest(req, t -> {
 399             if (t instanceof TransactionPreCommitSuccess) {
 400                 ret.voteYes();
 401             } else if (t instanceof RequestFailure) {
 402                 ret.voteNo(((RequestFailure<?, ?>) t).getCause());
 403             } else {
 404                 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
 405             }
 406
 407             recordSuccessfulRequest(req);
 408             LOG.debug("Transaction {} preCommit completed", this);
 409         });
 410     }
 411
 412     final void doCommit(final VotingFuture<?> ret) {
 413         checkReadWrite();
 414         checkSealed();
 415
 416         sendRequest(new TransactionDoCommitRequest(getIdentifier(), nextSequence(), localActor()), t -> {
 417             if (t instanceof TransactionCommitSuccess) {
 418                 ret.voteYes();
 419             } else if (t instanceof RequestFailure) {
 420                 ret.voteNo(((RequestFailure<?, ?>) t).getCause());
 421             } else {
 422                 ret.voteNo(new IllegalStateException("Unhandled response " + t.getClass()));
 423             }
 424
 425             LOG.debug("Transaction {} doCommit completed", this);
 426             parent.completeTransaction(this);
 427         });
 428     }
 429
 430     // Called with the connection unlocked
 431     final synchronized void startReconnect() {
 432         // At this point canCommit/directCommit are blocked, we assert a new successor state, retrieving the previous
 433         // state. This method is called with the queue still unlocked.
 434         final SuccessorState nextState = new SuccessorState();
 435         final State prevState = STATE_UPDATER.getAndSet(this, nextState);
 436
 437         LOG.debug("Start reconnect of proxy {} previous state {}", this, prevState);
 438         Verify.verify(!(prevState instanceof SuccessorState), "Proxy %s duplicate reconnect attempt after %s", this,
 439             prevState);
 440
 441         // We have asserted a slow-path state, seal(), canCommit(), directCommit() are forced to slow paths, which will
 442         // wait until we unblock nextState's latch before accessing state. Now we record prevState for later use and we
 443         // are done.
 444         nextState.setPrevState(prevState);
 445     }
 446
 447     // Called with the connection locked
 448     final void replayMessages(final AbstractProxyTransaction successor,
 449             final Iterable<ConnectionEntry> enqueuedEntries) {
 450         final SuccessorState local = getSuccessorState();
 451         local.setSuccessor(successor);
 452
 453         // Replay successful requests first
 454         for (Object obj : successfulRequests) {
 455             if (obj instanceof TransactionRequest) {
 456                 LOG.debug("Forwarding successful request {} to successor {}", obj, successor);
 457                 successor.handleForwardedRemoteRequest((TransactionRequest<?>) obj, null);
 458             } else {
 459                 Verify.verify(obj instanceof IncrementSequence);
 460                 successor.incrementSequence(((IncrementSequence) obj).getDelta());
 461             }
 462         }
 463         LOG.debug("{} replayed {} successful requests", getIdentifier(), successfulRequests.size());
 464         successfulRequests.clear();
 465
 466         // Now replay whatever is in the connection
 467         final Iterator<ConnectionEntry> it = enqueuedEntries.iterator();
 468         while (it.hasNext()) {
 469             final ConnectionEntry e = it.next();
 470             final Request<?, ?> req = e.getRequest();
 471
 472             if (getIdentifier().equals(req.getTarget())) {
 473                 Verify.verify(req instanceof TransactionRequest, "Unhandled request %s", req);
 474                 LOG.debug("Forwarding queued request{} to successor {}", req, successor);
 475                 successor.handleForwardedRemoteRequest((TransactionRequest<?>) req, e.getCallback());
 476                 it.remove();
 477             }
 478         }
 479
 480         /*
 481          * Check the state at which we have started the reconnect attempt. State transitions triggered while we were
 482          * reconnecting have been forced to slow paths, which will be unlocked once we unblock the state latch
 483          * at the end of this method.
 484          */
 485         final State prevState = local.getPrevState();
 486         if (SEALED.equals(prevState)) {
 487             LOG.debug("Proxy {} reconnected while being sealed, propagating state to successor {}", this, successor);
 488             flushState(successor);
 489             successor.seal();
 490         }
 491     }
 492
 493     // Called with the connection locked
 494     final void finishReconnect() {
 495         final SuccessorState local = getSuccessorState();
 496         LOG.debug("Finishing reconnect of proxy {}", this);
 497
 498         // All done, release the latch, unblocking seal() and canCommit() slow paths
 499         local.finish();
 500     }
 501
 502     /**
 503      * Invoked from a retired connection for requests which have been in-flight and need to be re-adjusted
 504      * and forwarded to the successor connection.
 505      *
 506      * @param request Request to be forwarded
 507      * @param callback Original callback
 508      */
 509     final void replayRequest(final TransactionRequest<?> request, final Consumer<Response<?, ?>> callback) {
 510         final AbstractProxyTransaction successor = getSuccessorState().getSuccessor();
 511
 512         if (successor instanceof LocalProxyTransaction) {
 513             forwardToLocal((LocalProxyTransaction)successor, request, callback);
 514         } else if (successor instanceof RemoteProxyTransaction) {
 515             forwardToRemote((RemoteProxyTransaction)successor, request, callback);
 516         } else {
 517             throw new IllegalStateException("Unhandled successor " + successor);
 518         }
 519     }
 520
 521     abstract boolean isSnapshotOnly();
 522
 523     abstract void doDelete(final YangInstanceIdentifier path);
 524
 525     abstract void doMerge(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data);
 526
 527     abstract void doWrite(final YangInstanceIdentifier path, final NormalizedNode<?, ?> data);
 528
 529     abstract CheckedFuture<Boolean, ReadFailedException> doExists(final YangInstanceIdentifier path);
 530
 531     abstract CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> doRead(
 532             final YangInstanceIdentifier path);
 533
 534     abstract void doSeal();
 535
 536     abstract void doAbort();
 537
 538     @GuardedBy("this")
 539     abstract void flushState(AbstractProxyTransaction successor);
 540
 541     abstract TransactionRequest<?> commitRequest(boolean coordinated);
 542
 543     /**
 544      * Invoked from {@link RemoteProxyTransaction} when it replays its successful requests to its successor. There is
 545      * no equivalent of this call from {@link LocalProxyTransaction} because it does not send a request until all
 546      * operations are packaged in the message.
 547      *
 548      * <p>
 549      * Note: this method is invoked by the predecessor on the successor.
 550      *
 551      * @param request Request which needs to be forwarded
 552      * @param callback Callback to be invoked once the request completes
 553      */
 554     abstract void handleForwardedRemoteRequest(TransactionRequest<?> request,
 555             @Nullable Consumer<Response<?, ?>> callback);
 556
 557     /**
 558      * Replay a request originating in this proxy to a successor remote proxy.
 559      */
 560     abstract void forwardToRemote(RemoteProxyTransaction successor, TransactionRequest<?> request,
 561             Consumer<Response<?, ?>> callback);
 562
 563     /**
 564      * Replay a request originating in this proxy to a successor local proxy.
 565      */
 566     abstract void forwardToLocal(LocalProxyTransaction successor, TransactionRequest<?> request,
 567             Consumer<Response<?, ?>> callback);
 568 }