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 javax.annotation.Nonnull;
  22 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  23 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  24 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  25 import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
  26 import org.opendaylight.controller.md.sal.common.api.data.TransactionChainClosedException;
  27 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
  28 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
  29 import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
  30 import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
  31 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
  32 import org.slf4j.Logger;
  33 import org.slf4j.LoggerFactory;
  34 import scala.concurrent.Future;
  35 import scala.concurrent.Promise;
  36
  37 /**
  38  * A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
  39  * at a time. For remote transactions, it also tracks the outstanding readiness requests
  40  * towards the shard and unblocks operations only after all have completed.
  41  */
  42 final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain>
  43         implements DOMStoreTransactionChain {
  44     private abstract static class State {
  45         /**
  46          * Check if it is okay to allocate a new transaction.
  47          * @throws IllegalStateException if a transaction may not be allocated.
  48          */
  49         abstract void checkReady();
  50
  51         /**
  52          * Return the future which needs to be waited for before shard information
  53          * is returned (which unblocks remote transactions).
  54          * @return Future to wait for, or null of no wait is necessary
  55          */
  56         abstract Future<?> previousFuture();
  57     }
  58
  59     private abstract static class Pending extends State {
  60         private final TransactionIdentifier transaction;
  61         private final Future<?> previousFuture;
  62
  63         Pending(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  64             this.previousFuture = previousFuture;
  65             this.transaction = Preconditions.checkNotNull(transaction);
  66         }
  67
  68         @Override
  69         final Future<?> previousFuture() {
  70             return previousFuture;
  71         }
  72
  73         final TransactionIdentifier getIdentifier() {
  74             return transaction;
  75         }
  76     }
  77
  78     private static final class Allocated extends Pending {
  79         Allocated(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  80             super(transaction, previousFuture);
  81         }
  82
  83         @Override
  84         void checkReady() {
  85             throw new IllegalStateException(String.format("Previous transaction %s is not ready yet", getIdentifier()));
  86         }
  87     }
  88
  89     private static final class Submitted extends Pending {
  90         Submitted(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  91             super(transaction, previousFuture);
  92         }
  93
  94         @Override
  95         void checkReady() {
  96             // Okay to allocate
  97         }
  98     }
  99
 100     private abstract static class DefaultState extends State {
 101         @Override
 102         final Future<?> previousFuture() {
 103             return null;
 104         }
 105     }
 106
 107     private static final State IDLE_STATE = new DefaultState() {
 108         @Override
 109         void checkReady() {
 110             // Okay to allocate
 111         }
 112     };
 113
 114     private static final State CLOSED_STATE = new DefaultState() {
 115         @Override
 116         void checkReady() {
 117             throw new TransactionChainClosedException("Transaction chain has been closed");
 118         }
 119     };
 120
 121     private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
 122     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
 123             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
 124
 125     private final TransactionContextFactory parent;
 126     private volatile State currentState = IDLE_STATE;
 127
 128     /**
 129      * This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
 130      * wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
 131      * asynchronous futures. Otherwise, in the following scenario, eg:
 132      * <p/>
 133      *   1) Create write tx1 on chain
 134      *   2) do write and submit
 135      *   3) Create read-only tx2 on chain and issue read
 136      *   4) Create write tx3 on chain, do write but do not submit
 137      * <p/>
 138      * if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
 139      * which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
 140      * (see Bug 4774).
 141      * <p/>
 142      * A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
 143      * lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
 144      * called which completes the Promise. A write tx that is created prior to completion will wait on the
 145      * Promise's Future via findPrimaryShard.
 146      */
 147     private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises =
 148             new ConcurrentHashMap<>();
 149
 150     TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
 151         super(parent.getActorContext(), historyId);
 152         this.parent = parent;
 153     }
 154
 155     @Override
 156     public DOMStoreReadTransaction newReadOnlyTransaction() {
 157         currentState.checkReady();
 158         TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
 159         priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
 160         return transactionProxy;
 161     }
 162
 163     @Override
 164     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
 165         getActorContext().acquireTxCreationPermit();
 166         return allocateWriteTransaction(TransactionType.READ_WRITE);
 167     }
 168
 169     @Override
 170     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 171         getActorContext().acquireTxCreationPermit();
 172         return allocateWriteTransaction(TransactionType.WRITE_ONLY);
 173     }
 174
 175     @Override
 176     public void close() {
 177         currentState = CLOSED_STATE;
 178
 179         // Send a close transaction chain request to each and every shard
 180
 181         getActorContext().broadcast(version -> new CloseTransactionChain(getHistoryId(), version).toSerializable(),
 182                 CloseTransactionChain.class);
 183     }
 184
 185     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
 186         State localState = currentState;
 187         localState.checkReady();
 188
 189         final TransactionProxy ret = new TransactionProxy(this, type);
 190         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
 191         return ret;
 192     }
 193
 194     @Override
 195     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader,
 196             final DataTree dataTree) {
 197         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
 198         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
 199         return ret;
 200     }
 201
 202     /**
 203      * This method is overridden to ensure the previous Tx's ready operations complete
 204      * before we initiate the next Tx in the chain to avoid creation failures if the
 205      * previous Tx's ready operations haven't completed yet.
 206      */
 207     @SuppressWarnings({ "unchecked", "rawtypes" })
 208     @Override
 209     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
 210         // Read current state atomically
 211         final State localState = currentState;
 212
 213         // There are no outstanding futures, shortcut
 214         Future<?> previous = localState.previousFuture();
 215         if (previous == null) {
 216             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
 217         }
 218
 219         final String previousTransactionId;
 220
 221         if (localState instanceof Pending) {
 222             previousTransactionId = ((Pending) localState).getIdentifier().toString();
 223             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
 224         } else {
 225             previousTransactionId = "";
 226             LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
 227         }
 228
 229         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
 230
 231         // Add a callback for completion of the combined Futures.
 232         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
 233
 234         final OnComplete onComplete = new OnComplete() {
 235             @Override
 236             public void onComplete(final Throwable failure, final Object notUsed) {
 237                 if (failure != null) {
 238                     // A Ready Future failed so fail the returned Promise.
 239                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
 240                     returnPromise.failure(failure);
 241                 } else {
 242                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
 243                             txId, previousTransactionId);
 244
 245                     // Send the FindPrimaryShard message and use the resulting Future to complete the
 246                     // returned Promise.
 247                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
 248                 }
 249             }
 250         };
 251
 252         previous.onComplete(onComplete, getActorContext().getClientDispatcher());
 253         return returnPromise.future();
 254     }
 255
 256     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
 257             final TransactionIdentifier txId) {
 258         if (!priorReadOnlyTxPromises.containsKey(txId) && !priorReadOnlyTxPromises.isEmpty()) {
 259             Collection<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
 260                     new ArrayList<>(priorReadOnlyTxPromises.entrySet());
 261             if (priorReadOnlyTxPromiseEntries.isEmpty()) {
 262                 return future;
 263             }
 264
 265             List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
 266             for (Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
 267                 LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
 268                 priorReadOnlyTxFutures.add(entry.getValue().future());
 269             }
 270
 271             Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
 272                     getActorContext().getClientDispatcher());
 273
 274             final Promise<T> returnPromise = Futures.promise();
 275             final OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 276                 @Override
 277                 public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
 278                     LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
 279
 280                     // Complete the returned Promise with the original Future.
 281                     returnPromise.completeWith(future);
 282                 }
 283             };
 284
 285             combinedFutures.onComplete(onComplete, getActorContext().getClientDispatcher());
 286             return returnPromise.future();
 287         } else {
 288             return future;
 289         }
 290     }
 291
 292     @Override
 293     protected <T> void onTransactionReady(final TransactionIdentifier transaction,
 294             final Collection<Future<T>> cohortFutures) {
 295         final State localState = currentState;
 296         Preconditions.checkState(localState instanceof Allocated, "Readying transaction %s while state is %s",
 297                 transaction, localState);
 298         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
 299         Preconditions.checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated",
 300                 transaction, currentTx);
 301
 302         // Transaction ready and we are not waiting for futures -- go to idle
 303         if (cohortFutures.isEmpty()) {
 304             currentState = IDLE_STATE;
 305             return;
 306         }
 307
 308         // Combine the ready Futures into 1
 309         final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorContext().getClientDispatcher());
 310
 311         // Record the we have outstanding futures
 312         final State newState = new Submitted(transaction, combined);
 313         currentState = newState;
 314
 315         // Attach a completion reset, but only if we do not allocate a transaction
 316         // in-between
 317         combined.onComplete(new OnComplete<Iterable<T>>() {
 318             @Override
 319             public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
 320                 STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
 321             }
 322         }, getActorContext().getClientDispatcher());
 323     }
 324
 325     @Override
 326     protected void onTransactionContextCreated(@Nonnull TransactionIdentifier transactionId) {
 327         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
 328         if (promise != null) {
 329             promise.success(null);
 330         }
 331     }
 332 }