opendaylight/md-sal/sal-distributed-datastore/src/main/java/org/opendaylight/controller/cluster/datastore/TransactionChainProxy.java

   1 /*
   2  * Copyright (c) 2015 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.datastore;
   9
  10 import akka.actor.ActorSelection;
  11 import akka.dispatch.Futures;
  12 import akka.dispatch.OnComplete;
  13 import com.google.common.base.Preconditions;
  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.concurrent.ConcurrentHashMap;
  19 import java.util.concurrent.ConcurrentMap;
  20 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  21 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  22 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  23 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  24 import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
  25 import org.opendaylight.mdsal.dom.api.DOMTransactionChainClosedException;
  26 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadTransaction;
  27 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadWriteTransaction;
  28 import org.opendaylight.mdsal.dom.spi.store.DOMStoreTransactionChain;
  29 import org.opendaylight.mdsal.dom.spi.store.DOMStoreWriteTransaction;
  30 import org.opendaylight.yangtools.yang.data.api.schema.tree.ReadOnlyDataTree;
  31 import org.slf4j.Logger;
  32 import org.slf4j.LoggerFactory;
  33 import scala.concurrent.Future;
  34 import scala.concurrent.Promise;
  35
  36 /**
  37  * A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
  38  * at a time. For remote transactions, it also tracks the outstanding readiness requests
  39  * towards the shard and unblocks operations only after all have completed.
  40  */
  41 final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain>
  42         implements DOMStoreTransactionChain {
  43     private abstract static class State {
  44         /**
  45          * Check if it is okay to allocate a new transaction.
  46          * @throws IllegalStateException if a transaction may not be allocated.
  47          */
  48         abstract void checkReady();
  49
  50         /**
  51          * Return the future which needs to be waited for before shard information
  52          * is returned (which unblocks remote transactions).
  53          * @return Future to wait for, or null of no wait is necessary
  54          */
  55         abstract Future<?> previousFuture();
  56     }
  57
  58     private abstract static class Pending extends State {
  59         private final TransactionIdentifier transaction;
  60         private final Future<?> previousFuture;
  61
  62         Pending(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  63             this.previousFuture = previousFuture;
  64             this.transaction = Preconditions.checkNotNull(transaction);
  65         }
  66
  67         @Override
  68         final Future<?> previousFuture() {
  69             return previousFuture;
  70         }
  71
  72         final TransactionIdentifier getIdentifier() {
  73             return transaction;
  74         }
  75     }
  76
  77     private static final class Allocated extends Pending {
  78         Allocated(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  79             super(transaction, previousFuture);
  80         }
  81
  82         @Override
  83         void checkReady() {
  84             throw new IllegalStateException(String.format("Previous transaction %s is not ready yet", getIdentifier()));
  85         }
  86     }
  87
  88     private static final class Submitted extends Pending {
  89         Submitted(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  90             super(transaction, previousFuture);
  91         }
  92
  93         @Override
  94         void checkReady() {
  95             // Okay to allocate
  96         }
  97     }
  98
  99     private abstract static class DefaultState extends State {
 100         @Override
 101         final Future<?> previousFuture() {
 102             return null;
 103         }
 104     }
 105
 106     private static final State IDLE_STATE = new DefaultState() {
 107         @Override
 108         void checkReady() {
 109             // Okay to allocate
 110         }
 111     };
 112
 113     private static final State CLOSED_STATE = new DefaultState() {
 114         @Override
 115         void checkReady() {
 116             throw new DOMTransactionChainClosedException("Transaction chain has been closed");
 117         }
 118     };
 119
 120     private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
 121     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
 122             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
 123
 124     private final TransactionContextFactory parent;
 125     private volatile State currentState = IDLE_STATE;
 126
 127     /**
 128      * This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
 129      * wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
 130      * asynchronous futures. Otherwise, in the following scenario, eg:
 131      * <p/>
 132      *   1) Create write tx1 on chain
 133      *   2) do write and submit
 134      *   3) Create read-only tx2 on chain and issue read
 135      *   4) Create write tx3 on chain, do write but do not submit
 136      * <p/>
 137      * if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
 138      * which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
 139      * (see Bug 4774).
 140      * <p/>
 141      * A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
 142      * lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
 143      * called which completes the Promise. A write tx that is created prior to completion will wait on the
 144      * Promise's Future via findPrimaryShard.
 145      */
 146     private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises =
 147             new ConcurrentHashMap<>();
 148
 149     TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
 150         super(parent.getActorUtils(), historyId);
 151         this.parent = parent;
 152     }
 153
 154     @Override
 155     public DOMStoreReadTransaction newReadOnlyTransaction() {
 156         currentState.checkReady();
 157         TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
 158         priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
 159         return transactionProxy;
 160     }
 161
 162     @Override
 163     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
 164         getActorUtils().acquireTxCreationPermit();
 165         return allocateWriteTransaction(TransactionType.READ_WRITE);
 166     }
 167
 168     @Override
 169     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 170         getActorUtils().acquireTxCreationPermit();
 171         return allocateWriteTransaction(TransactionType.WRITE_ONLY);
 172     }
 173
 174     @Override
 175     public void close() {
 176         currentState = CLOSED_STATE;
 177
 178         // Send a close transaction chain request to each and every shard
 179
 180         getActorUtils().broadcast(version -> new CloseTransactionChain(getHistoryId(), version).toSerializable(),
 181                 CloseTransactionChain.class);
 182     }
 183
 184     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
 185         State localState = currentState;
 186         localState.checkReady();
 187
 188         final TransactionProxy ret = new TransactionProxy(this, type);
 189         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
 190         return ret;
 191     }
 192
 193     @Override
 194     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader,
 195             final ReadOnlyDataTree dataTree) {
 196         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
 197         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
 198         return ret;
 199     }
 200
 201     /**
 202      * This method is overridden to ensure the previous Tx's ready operations complete
 203      * before we initiate the next Tx in the chain to avoid creation failures if the
 204      * previous Tx's ready operations haven't completed yet.
 205      */
 206     @SuppressWarnings({ "unchecked", "rawtypes" })
 207     @Override
 208     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
 209         // Read current state atomically
 210         final State localState = currentState;
 211
 212         // There are no outstanding futures, shortcut
 213         Future<?> previous = localState.previousFuture();
 214         if (previous == null) {
 215             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
 216         }
 217
 218         final String previousTransactionId;
 219
 220         if (localState instanceof Pending) {
 221             previousTransactionId = ((Pending) localState).getIdentifier().toString();
 222             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
 223         } else {
 224             previousTransactionId = "";
 225             LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
 226         }
 227
 228         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
 229
 230         // Add a callback for completion of the combined Futures.
 231         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
 232
 233         final OnComplete onComplete = new OnComplete() {
 234             @Override
 235             public void onComplete(final Throwable failure, final Object notUsed) {
 236                 if (failure != null) {
 237                     // A Ready Future failed so fail the returned Promise.
 238                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
 239                     returnPromise.failure(failure);
 240                 } else {
 241                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
 242                             txId, previousTransactionId);
 243
 244                     // Send the FindPrimaryShard message and use the resulting Future to complete the
 245                     // returned Promise.
 246                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
 247                 }
 248             }
 249         };
 250
 251         previous.onComplete(onComplete, getActorUtils().getClientDispatcher());
 252         return returnPromise.future();
 253     }
 254
 255     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
 256             final TransactionIdentifier txId) {
 257         if (!priorReadOnlyTxPromises.containsKey(txId) && !priorReadOnlyTxPromises.isEmpty()) {
 258             Collection<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
 259                     new ArrayList<>(priorReadOnlyTxPromises.entrySet());
 260             if (priorReadOnlyTxPromiseEntries.isEmpty()) {
 261                 return future;
 262             }
 263
 264             List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
 265             for (Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
 266                 LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
 267                 priorReadOnlyTxFutures.add(entry.getValue().future());
 268             }
 269
 270             Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
 271                     getActorUtils().getClientDispatcher());
 272
 273             final Promise<T> returnPromise = Futures.promise();
 274             final OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 275                 @Override
 276                 public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
 277                     LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
 278
 279                     // Complete the returned Promise with the original Future.
 280                     returnPromise.completeWith(future);
 281                 }
 282             };
 283
 284             combinedFutures.onComplete(onComplete, getActorUtils().getClientDispatcher());
 285             return returnPromise.future();
 286         } else {
 287             return future;
 288         }
 289     }
 290
 291     @Override
 292     protected <T> void onTransactionReady(final TransactionIdentifier transaction,
 293             final Collection<Future<T>> cohortFutures) {
 294         final State localState = currentState;
 295         Preconditions.checkState(localState instanceof Allocated, "Readying transaction %s while state is %s",
 296                 transaction, localState);
 297         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
 298         Preconditions.checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated",
 299                 transaction, currentTx);
 300
 301         // Transaction ready and we are not waiting for futures -- go to idle
 302         if (cohortFutures.isEmpty()) {
 303             currentState = IDLE_STATE;
 304             return;
 305         }
 306
 307         // Combine the ready Futures into 1
 308         final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorUtils().getClientDispatcher());
 309
 310         // Record the we have outstanding futures
 311         final State newState = new Submitted(transaction, combined);
 312         currentState = newState;
 313
 314         // Attach a completion reset, but only if we do not allocate a transaction
 315         // in-between
 316         combined.onComplete(new OnComplete<Iterable<T>>() {
 317             @Override
 318             public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
 319                 STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
 320             }
 321         }, getActorUtils().getClientDispatcher());
 322     }
 323
 324     @Override
 325     protected void onTransactionContextCreated(TransactionIdentifier transactionId) {
 326         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
 327         if (promise != null) {
 328             promise.success(null);
 329         }
 330     }
 331 }