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.AtomicInteger;
  21 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  22 import java.util.function.Function;
  23 import javax.annotation.Nonnull;
  24 import org.opendaylight.controller.cluster.datastore.identifiers.TransactionChainIdentifier;
  25 import org.opendaylight.controller.cluster.datastore.identifiers.TransactionIdentifier;
  26 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  27 import org.opendaylight.controller.cluster.datastore.messages.PrimaryShardInfo;
  28 import org.opendaylight.controller.md.sal.common.api.data.TransactionChainClosedException;
  29 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
  30 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
  31 import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
  32 import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
  33 import org.opendaylight.yangtools.yang.data.api.schema.tree.DataTree;
  34 import org.slf4j.Logger;
  35 import org.slf4j.LoggerFactory;
  36 import scala.concurrent.Future;
  37 import scala.concurrent.Promise;
  38
  39 /**
  40  * A chain of {@link TransactionProxy}s. It allows a single open transaction to be open
  41  * at a time. For remote transactions, it also tracks the outstanding readiness requests
  42  * towards the shard and unblocks operations only after all have completed.
  43  */
  44 final class TransactionChainProxy extends AbstractTransactionContextFactory<LocalTransactionChain> implements DOMStoreTransactionChain {
  45     private static abstract 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 static abstract 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 = Preconditions.checkNotNull(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 static abstract 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 TransactionChainClosedException("Transaction chain has been closed");
 119         }
 120     };
 121
 122     private static final Logger LOG = LoggerFactory.getLogger(TransactionChainProxy.class);
 123     private static final AtomicInteger CHAIN_COUNTER = new AtomicInteger();
 124     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
 125             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "currentState");
 126
 127     private final TransactionChainIdentifier transactionChainId;
 128     private final TransactionContextFactory parent;
 129     private volatile State currentState = IDLE_STATE;
 130
 131     /**
 132      * This map holds Promise instances for each read-only tx. It is used to maintain ordering of tx creates
 133      * wrt to read-only tx's between this class and a LocalTransactionChain since they're bridged by
 134      * asynchronous futures. Otherwise, in the following scenario, eg:
 135      *
 136      *   1) Create write tx1 on chain
 137      *   2) do write and submit
 138      *   3) Create read-only tx2 on chain and issue read
 139      *   4) Create write tx3 on chain, do write but do not submit
 140      *
 141      * if the sequence/timing is right, tx3 may create its local tx on the LocalTransactionChain before tx2,
 142      * which results in tx2 failing b/c tx3 isn't ready yet. So maintaining ordering prevents this issue
 143      * (see Bug 4774).
 144      * <p>
 145      * A Promise is added via newReadOnlyTransaction. When the parent class completes the primary shard
 146      * lookup and creates the TransactionContext (either success or failure), onTransactionContextCreated is
 147      * called which completes the Promise. A write tx that is created prior to completion will wait on the
 148      * Promise's Future via findPrimaryShard.
 149      */
 150     private final ConcurrentMap<TransactionIdentifier, Promise<Object>> priorReadOnlyTxPromises = new ConcurrentHashMap<>();
 151
 152     TransactionChainProxy(final TransactionContextFactory parent) {
 153         super(parent.getActorContext());
 154
 155         transactionChainId = new TransactionChainIdentifier(parent.getActorContext().getCurrentMemberName(), CHAIN_COUNTER.incrementAndGet());
 156         this.parent = parent;
 157     }
 158
 159     public String getTransactionChainId() {
 160         return transactionChainId.toString();
 161     }
 162
 163     @Override
 164     public DOMStoreReadTransaction newReadOnlyTransaction() {
 165         currentState.checkReady();
 166         TransactionProxy transactionProxy = new TransactionProxy(this, TransactionType.READ_ONLY);
 167         priorReadOnlyTxPromises.put(transactionProxy.getIdentifier(), Futures.<Object>promise());
 168         return transactionProxy;
 169     }
 170
 171     @Override
 172     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
 173         getActorContext().acquireTxCreationPermit();
 174         return allocateWriteTransaction(TransactionType.READ_WRITE);
 175     }
 176
 177     @Override
 178     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 179         getActorContext().acquireTxCreationPermit();
 180         return allocateWriteTransaction(TransactionType.WRITE_ONLY);
 181     }
 182
 183     @Override
 184     public void close() {
 185         currentState = CLOSED_STATE;
 186
 187         // Send a close transaction chain request to each and every shard
 188
 189         getActorContext().broadcast(new Function<Short, Object>() {
 190             @Override
 191             public Object apply(Short version) {
 192                 return new CloseTransactionChain(transactionChainId.toString(), version).toSerializable();
 193             }
 194         });
 195     }
 196
 197     private TransactionProxy allocateWriteTransaction(final TransactionType type) {
 198         State localState = currentState;
 199         localState.checkReady();
 200
 201         final TransactionProxy ret = new TransactionProxy(this, type);
 202         currentState = new Allocated(ret.getIdentifier(), localState.previousFuture());
 203         return ret;
 204     }
 205
 206     @Override
 207     protected LocalTransactionChain factoryForShard(final String shardName, final ActorSelection shardLeader, final DataTree dataTree) {
 208         final LocalTransactionChain ret = new LocalTransactionChain(this, shardLeader, dataTree);
 209         LOG.debug("Allocated transaction chain {} for shard {} leader {}", ret, shardName, shardLeader);
 210         return ret;
 211     }
 212
 213     /**
 214      * This method is overridden to ensure the previous Tx's ready operations complete
 215      * before we initiate the next Tx in the chain to avoid creation failures if the
 216      * previous Tx's ready operations haven't completed yet.
 217      */
 218     @SuppressWarnings({ "unchecked", "rawtypes" })
 219     @Override
 220     protected Future<PrimaryShardInfo> findPrimaryShard(final String shardName, final TransactionIdentifier txId) {
 221         // Read current state atomically
 222         final State localState = currentState;
 223
 224         // There are no outstanding futures, shortcut
 225         Future<?> previous = localState.previousFuture();
 226         if (previous == null) {
 227             return combineFutureWithPossiblePriorReadOnlyTxFutures(parent.findPrimaryShard(shardName, txId), txId);
 228         }
 229
 230         final String previousTransactionId;
 231
 232         if(localState instanceof Pending){
 233             previousTransactionId = ((Pending) localState).getIdentifier().toString();
 234             LOG.debug("Tx: {} - waiting for ready futures with pending Tx {}", txId, previousTransactionId);
 235         } else {
 236             previousTransactionId = "";
 237             LOG.debug("Waiting for ready futures on chain {}", getTransactionChainId());
 238         }
 239
 240         previous = combineFutureWithPossiblePriorReadOnlyTxFutures(previous, txId);
 241
 242         // Add a callback for completion of the combined Futures.
 243         final Promise<PrimaryShardInfo> returnPromise = Futures.promise();
 244
 245         final OnComplete onComplete = new OnComplete() {
 246             @Override
 247             public void onComplete(final Throwable failure, final Object notUsed) {
 248                 if (failure != null) {
 249                     // A Ready Future failed so fail the returned Promise.
 250                     LOG.error("Tx: {} - ready future failed for previous Tx {}", txId, previousTransactionId);
 251                     returnPromise.failure(failure);
 252                 } else {
 253                     LOG.debug("Tx: {} - previous Tx {} readied - proceeding to FindPrimaryShard",
 254                             txId, previousTransactionId);
 255
 256                     // Send the FindPrimaryShard message and use the resulting Future to complete the
 257                     // returned Promise.
 258                     returnPromise.completeWith(parent.findPrimaryShard(shardName, txId));
 259                 }
 260             }
 261         };
 262
 263         previous.onComplete(onComplete, getActorContext().getClientDispatcher());
 264         return returnPromise.future();
 265     }
 266
 267     private <T> Future<T> combineFutureWithPossiblePriorReadOnlyTxFutures(final Future<T> future,
 268             final TransactionIdentifier txId) {
 269         if(!priorReadOnlyTxPromises.containsKey(txId) && !priorReadOnlyTxPromises.isEmpty()) {
 270             Collection<Entry<TransactionIdentifier, Promise<Object>>> priorReadOnlyTxPromiseEntries =
 271                     new ArrayList<>(priorReadOnlyTxPromises.entrySet());
 272             if(priorReadOnlyTxPromiseEntries.isEmpty()) {
 273                 return future;
 274             }
 275
 276             List<Future<Object>> priorReadOnlyTxFutures = new ArrayList<>(priorReadOnlyTxPromiseEntries.size());
 277             for(Entry<TransactionIdentifier, Promise<Object>> entry: priorReadOnlyTxPromiseEntries) {
 278                 LOG.debug("Tx: {} - waiting on future for prior read-only Tx {}", txId, entry.getKey());
 279                 priorReadOnlyTxFutures.add(entry.getValue().future());
 280             }
 281
 282             Future<Iterable<Object>> combinedFutures = Futures.sequence(priorReadOnlyTxFutures,
 283                     getActorContext().getClientDispatcher());
 284
 285             final Promise<T> returnPromise = Futures.promise();
 286             final OnComplete<Iterable<Object>> onComplete = new OnComplete<Iterable<Object>>() {
 287                 @Override
 288                 public void onComplete(final Throwable failure, final Iterable<Object> notUsed) {
 289                     LOG.debug("Tx: {} - prior read-only Tx futures complete", txId);
 290
 291                     // Complete the returned Promise with the original Future.
 292                     returnPromise.completeWith(future);
 293                 }
 294             };
 295
 296             combinedFutures.onComplete(onComplete, getActorContext().getClientDispatcher());
 297             return returnPromise.future();
 298         } else {
 299             return future;
 300         }
 301     }
 302
 303     @Override
 304     protected <T> void onTransactionReady(final TransactionIdentifier transaction, final Collection<Future<T>> cohortFutures) {
 305         final State localState = currentState;
 306         Preconditions.checkState(localState instanceof Allocated, "Readying transaction %s while state is %s", transaction, localState);
 307         final TransactionIdentifier currentTx = ((Allocated)localState).getIdentifier();
 308         Preconditions.checkState(transaction.equals(currentTx), "Readying transaction %s while %s is allocated", transaction, currentTx);
 309
 310         // Transaction ready and we are not waiting for futures -- go to idle
 311         if (cohortFutures.isEmpty()) {
 312             currentState = IDLE_STATE;
 313             return;
 314         }
 315
 316         // Combine the ready Futures into 1
 317         final Future<Iterable<T>> combined = Futures.sequence(cohortFutures, getActorContext().getClientDispatcher());
 318
 319         // Record the we have outstanding futures
 320         final State newState = new Submitted(transaction, combined);
 321         currentState = newState;
 322
 323         // Attach a completion reset, but only if we do not allocate a transaction
 324         // in-between
 325         combined.onComplete(new OnComplete<Iterable<T>>() {
 326             @Override
 327             public void onComplete(final Throwable arg0, final Iterable<T> arg1) {
 328                 STATE_UPDATER.compareAndSet(TransactionChainProxy.this, newState, IDLE_STATE);
 329             }
 330         }, getActorContext().getClientDispatcher());
 331     }
 332
 333     @Override
 334     protected void onTransactionContextCreated(@Nonnull TransactionIdentifier transactionId) {
 335         Promise<Object> promise = priorReadOnlyTxPromises.remove(transactionId);
 336         if(promise != null) {
 337             promise.success(null);
 338         }
 339     }
 340
 341     @Override
 342     protected TransactionIdentifier nextIdentifier() {
 343         return transactionChainId.newTransactionIdentifier();
 344     }
 345 }