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 static com.google.common.base.Preconditions.checkState;
  11 import static java.util.Objects.requireNonNull;
  12
  13 import akka.actor.ActorSelection;
  14 import akka.dispatch.Futures;
  15 import akka.dispatch.OnComplete;
  16 import java.util.ArrayList;
  17 import java.util.Collection;
  18 import java.util.List;
  19 import java.util.Map.Entry;
  20 import java.util.concurrent.ConcurrentHashMap;
  21 import java.util.concurrent.ConcurrentMap;
  22 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  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.mdsal.dom.api.DOMTransactionChainClosedException;
  28 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadTransaction;
  29 import org.opendaylight.mdsal.dom.spi.store.DOMStoreReadWriteTransaction;
  30 import org.opendaylight.mdsal.dom.spi.store.DOMStoreTransactionChain;
  31 import org.opendaylight.mdsal.dom.spi.store.DOMStoreWriteTransaction;
  32 import org.opendaylight.yangtools.yang.data.api.schema.tree.ReadOnlyDataTree;
  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>
  44         implements DOMStoreTransactionChain {
  45     private abstract static class State {
  46         /**
  47          * Check if it is okay to allocate a new transaction.
  48          * @throws IllegalStateException if a transaction may not be allocated.
  49          */
  50         abstract void checkReady();
  51
  52         /**
  53          * Return the future which needs to be waited for before shard information
  54          * is returned (which unblocks remote transactions).
  55          * @return Future to wait for, or null of no wait is necessary
  56          */
  57         abstract Future<?> previousFuture();
  58     }
  59
  60     private abstract static class Pending extends State {
  61         private final TransactionIdentifier transaction;
  62         private final Future<?> previousFuture;
  63
  64         Pending(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  65             this.previousFuture = previousFuture;
  66             this.transaction = requireNonNull(transaction);
  67         }
  68
  69         @Override
  70         final Future<?> previousFuture() {
  71             return previousFuture;
  72         }
  73
  74         final TransactionIdentifier getIdentifier() {
  75             return transaction;
  76         }
  77     }
  78
  79     private static final class Allocated extends Pending {
  80         Allocated(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  81             super(transaction, previousFuture);
  82         }
  83
  84         @Override
  85         void checkReady() {
  86             throw new IllegalStateException(String.format("Previous transaction %s is not ready yet", getIdentifier()));
  87         }
  88     }
  89
  90     private static final class Submitted extends Pending {
  91         Submitted(final TransactionIdentifier transaction, final Future<?> previousFuture) {
  92             super(transaction, previousFuture);
  93         }
  94
  95         @Override
  96         void checkReady() {
  97             // Okay to allocate
  98         }
  99     }
 100
 101     private abstract static class DefaultState extends State {
 102         @Override
 103         final Future<?> previousFuture() {
 104             return null;
 105         }
 106     }
 107
 108     private static final State IDLE_STATE = new DefaultState() {
 109         @Override
 110         void checkReady() {
 111             // Okay to allocate
 112         }
 113     };
 114
 115     private static final State CLOSED_STATE = new DefaultState() {
 116         @Override
 117         void checkReady() {
 118             throw new DOMTransactionChainClosedException("Transaction chain has been closed");
 119         }
 120     };
 121
 122     private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
 123     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
 124             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
 125
 126     private final TransactionContextFactory parent;
 127     private volatile State currentState = IDLE_STATE;
 128
 129     /**
 130      * This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
 131      * wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
 132      * asynchronous futures. Otherwise, in the following scenario, eg:
 133      * <p/>
 134      *   1) Create write tx1 on chain
 135      *   2) do write and submit
 136      *   3) Create read-only tx2 on chain and issue read
 137      *   4) Create write tx3 on chain, do write but do not submit
 138      * <p/>
 139      * if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
 140      * which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
 141      * (see Bug 4774).
 142      * <p/>
 143      * A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
 144      * lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
 145      * called which completes the Promise. A write tx that is created prior to completion will wait on the
 146      * Promise's Future via findPrimaryShard.
 147      */
 148     private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises =
 149             new ConcurrentHashMap<>();
 150
 151     TransactionChainProxy(final TransactionContextFactory parent, final LocalHistoryIdentifier historyId) {
 152         super(parent.getActorUtils(), historyId);
 153         this.parent = parent;
 154     }
 155
 156     @Override
 157     public DOMStoreReadTransaction newReadOnlyTransaction() {
 158         currentState.checkReady();
 159         TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
 160         priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
 161         return transactionProxy;
 162     }
 163
 164     @Override
 165     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
 166         getActorUtils().acquireTxCreationPermit();
 167         return allocateWriteTransaction(TransactionType.READ_WRITE);
 168     }
 169
 170     @Override
 171     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 172         getActorUtils().acquireTxCreationPermit();
 173         return allocateWriteTransaction(TransactionType.WRITE_ONLY);
 174     }
 175
 176     @Override
 177     public void close() {
 178         currentState = CLOSED_STATE;
 179
 180         // Send a close transaction chain request to each and every shard
 181
 182         getActorUtils().broadcast(version -> new CloseTransactionChain(getHistoryId(), version).toSerializable(),
 183                 CloseTransactionChain.class);
 184     }
 185
 186     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
 187         State localState = currentState;
 188         localState.checkReady();
 189
 190         final TransactionProxy ret = new TransactionProxy(this, type);
 191         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
 192         return ret;
 193     }
 194
 195     @Override
 196     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader,
 197             final ReadOnlyDataTree dataTree) {
 198         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
 199         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
 200         return ret;
 201     }
 202
 203     /**
 204      * This method is overridden to ensure the previous Tx's ready operations complete
 205      * before we initiate the next Tx in the chain to avoid creation failures if the
 206      * previous Tx's ready operations haven't completed yet.
 207      */
 208     @SuppressWarnings({ "unchecked", "rawtypes" })
 209     @Override
 210     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
 211         // Read current state atomically
 212         final State localState = currentState;
 213
 214         // There are no outstanding futures, shortcut
 215         Future<?> previous = localState.previousFuture();
 216         if (previous == null) {
 217             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
 218         }
 219
 220         final String previousTransactionId;
 221
 222         if (localState instanceof Pending) {
 223             previousTransactionId = ((Pending) localState).getIdentifier().toString();
 224             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
 225         } else {
 226             previousTransactionId = "";
 227             LOG.debug("Waiting for ready futures on chain {}", getHistoryId());
 228         }
 229
 230         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
 231
 232         // Add a callback for completion of the combined Futures.
 233         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
 234
 235         final OnComplete onComplete = new OnComplete() {
 236             @Override
 237             public void onComplete(final Throwable failure, final Object notUsed) {
 238                 if (failure != null) {
 239                     // A Ready Future failed so fail the returned Promise.
 240                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
 241                     returnPromise.failure(failure);
 242                 } else {
 243                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
 244                             txId, previousTransactionId);
 245
 246                     // Send the FindPrimaryShard message and use the resulting Future to complete the
 247                     // returned Promise.
 248                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
 249                 }
 250             }
 251         };
 252
 253         previous.onComplete(onComplete, getActorUtils().getClientDispatcher());
 254         return returnPromise.future();
 255     }
 256
 257     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
 258             final TransactionIdentifier txId) {
 259         return priorReadOnlyTxPromises.isEmpty() || priorReadOnlyTxPromises.containsKey(txId) ? future
 260                 // Tough luck, we need do some work
 261                 : combineWithPriorReadOnlyTxFutures(future, txId);
 262     }
 263
 264     // Split out of the common path
 265     private <T> Future<T> combineWithPriorReadOnlyTxFutures(final Future<T> future, final TransactionIdentifier txId) {
 266         // Take a stable snapshot, and check if we raced
 267         final List<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
 268                 new ArrayList<>(priorReadOnlyTxPromises.entrySet());
 269         if (priorReadOnlyTxPromiseEntries.isEmpty()) {
 270             return future;
 271         }
 272
 273         final List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
 274         for (Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
 275             LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
 276             priorReadOnlyTxFutures.add(entry.getValue().future());
 277         }
 278
 279         final Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
 280             getActorUtils().getClientDispatcher());
 281
 282         final Promise<T> returnPromise = Futures.promise();
 283         final OnComplete<Iterable<Object>> onComplete = new OnComplete<>() {
 284             @Override
 285             public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
 286                 LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
 287
 288                 // Complete the returned Promise with the original Future.
 289                 returnPromise.completeWith(future);
 290             }
 291         };
 292
 293         combinedFutures.onComplete(onComplete, getActorUtils().getClientDispatcher());
 294         return returnPromise.future();
 295     }
 296
 297     @Override
 298     protected <T> void onTransactionReady(final TransactionIdentifier transaction,
 299             final Collection<Future<T>> cohortFutures) {
 300         final State localState = currentState;
 301         checkState(localState instanceof Allocated, "Readying transaction %s while state is %s", transaction,
 302             localState);
 303         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
 304         checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated", transaction,
 305             currentTx);
 306
 307         // Transaction ready and we are not waiting for futures -- go to idle
 308         if (cohortFutures.isEmpty()) {
 309             currentState = IDLE_STATE;
 310             return;
 311         }
 312
 313         // Combine the ready Futures into 1
 314         final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorUtils().getClientDispatcher());
 315
 316         // Record the we have outstanding futures
 317         final State newState = new Submitted(transaction, combined);
 318         currentState = newState;
 319
 320         // Attach a completion reset, but only if we do not allocate a transaction
 321         // in-between
 322         combined.onComplete(new OnComplete<Iterable<T>>() {
 323             @Override
 324             public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
 325                 STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
 326             }
 327         }, getActorUtils().getClientDispatcher());
 328     }
 329
 330     @Override
 331     protected void onTransactionContextCreated(final TransactionIdentifier transactionId) {
 332         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
 333         if (promise != null) {
 334             promise.success(null);
 335         }
 336     }
 337 }