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 java.util.function.Function;
  22 import javax.annotation.Nonnull;
  23 import org.opendaylight.controller.cluster.access.concepts.LocalHistoryIdentifier;
  24 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  25 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  26 import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
  27 import org.opendaylight.controller.md.sal.common.api.data.TransactionChainClosedException;
  28 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
  29 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
  30 import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
  31 import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
  32 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
  33 import org.slf4j.Logger;
  34 import org.slf4j.LoggerFactory;
  35 import scala.concurrent.Future;
  36 import scala.concurrent.Promise;
  37
  38 /**
  39  * A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
  40  * at a time. For remote transactions, it also tracks the outstanding readiness requests
  41  * towards the shard and unblocks operations only after all have completed.
  42  */
  43 final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain> implements DOMStoreTransactionChain {
  44     private static abstract 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 static abstract 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 static abstract 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      *
 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      *
 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 = new ConcurrentHashMap<>();
 148
 149     TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
 150         super(parent.getActorContext(), 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         getActorContext().acquireTxCreationPermit();
 165         return allocateWriteTransaction(TransactionType.READ_WRITE);
 166     }
 167
 168     @Override
 169     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 170         getActorContext().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         getActorContext().broadcast(new Function<Short, Object>() {
 181             @Override
 182             public Object apply(Short version) {
 183                 return new CloseTransactionChain(getHistoryId(), version).toSerializable();
 184             }
 185         }, CloseTransactionChain.class);
 186     }
 187
 188     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
 189         State localState = currentState;
 190         localState.checkReady();
 191
 192         final TransactionProxy ret = new TransactionProxy(this, type);
 193         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
 194         return ret;
 195     }
 196
 197     @Override
 198     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader, final DataTree dataTree) {
 199         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
 200         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
 201         return ret;
 202     }
 203
 204     /**
 205      * This method is overridden to ensure the previous Tx's ready operations complete
 206      * before we initiate the next Tx in the chain to avoid creation failures if the
 207      * previous Tx's ready operations haven't completed yet.
 208      */
 209     @SuppressWarnings({ "unchecked", "rawtypes" })
 210     @Override
 211     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
 212         // Read current state atomically
 213         final State localState = currentState;
 214
 215         // There are no outstanding futures, shortcut
 216         Future<?> previous = localState.previousFuture();
 217         if (previous == null) {
 218             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
 219         }
 220
 221         final String previousTransactionId;
 222
 223         if(localState instanceof Pending){
 224             previousTransactionId = ((Pending) localState).getIdentifier().toString();
 225             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
 226         } else {
 227             previousTransactionId = "";
 228             LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
 229         }
 230
 231         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
 232
 233         // Add a callback for completion of the combined Futures.
 234         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
 235
 236         final OnComplete onComplete = new OnComplete() {
 237             @Override
 238             public void onComplete(final Throwable failure, final Object notUsed) {
 239                 if (failure != null) {
 240                     // A Ready Future failed so fail the returned Promise.
 241                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
 242                     returnPromise.failure(failure);
 243                 } else {
 244                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
 245                             txId, previousTransactionId);
 246
 247                     // Send the FindPrimaryShard message and use the resulting Future to complete the
 248                     // returned Promise.
 249                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
 250                 }
 251             }
 252         };
 253
 254         previous.onComplete(onComplete, getActorContext().getClientDispatcher());
 255         return returnPromise.future();
 256     }
 257
 258     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
 259             final TransactionIdentifier txId) {
 260         if(!priorReadOnlyTxPromises.containsKey(txId) && !priorReadOnlyTxPromises.isEmpty()) {
 261             Collection<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
 262                     new ArrayList<>(priorReadOnlyTxPromises.entrySet());
 263             if(priorReadOnlyTxPromiseEntries.isEmpty()) {
 264                 return future;
 265             }
 266
 267             List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
 268             for(Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
 269                 LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
 270                 priorReadOnlyTxFutures.add(entry.getValue().future());
 271             }
 272
 273             Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
 274                     getActorContext().getClientDispatcher());
 275
 276             final Promise<T> returnPromise = Futures.promise();
 277             final OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 278                 @Override
 279                 public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
 280                     LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
 281
 282                     // Complete the returned Promise with the original Future.
 283                     returnPromise.completeWith(future);
 284                 }
 285             };
 286
 287             combinedFutures.onComplete(onComplete, getActorContext().getClientDispatcher());
 288             return returnPromise.future();
 289         } else {
 290             return future;
 291         }
 292     }
 293
 294     @Override
 295     protected <T> void onTransactionReady(final TransactionIdentifier transaction, final Collection<Future<T>> cohortFutures) {
 296         final State localState = currentState;
 297         Preconditions.checkState(localState instanceof Allocated, "Readying transaction %s while state is %s", transaction, localState);
 298         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
 299         Preconditions.checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated", 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, getActorContext().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         }, getActorContext().getClientDispatcher());
 322     }
 323
 324     @Override
 325     protected void onTransactionContextCreated(@Nonnull TransactionIdentifier transactionId) {
 326         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
 327         if(promise != null) {
 328             promise.success(null);
 329         }
 330     }
 331 }