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

   1 /*
   2  * Copyright (c) 2014 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
   9 package org.opendaylight.controller.cluster.datastore;
  10
  11 import akka.actor.ActorSelection;
  12 import akka.dispatch.OnComplete;
  13 import com.google.common.base.Preconditions;
  14 import java.util.AbstractMap.SimpleEntry;
  15 import java.util.Collections;
  16 import java.util.List;
  17 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;
  18 import org.opendaylight.controller.cluster.datastore.messages.CloseTransactionChain;
  19 import org.opendaylight.controller.cluster.datastore.utils.ActorContext;
  20 import org.opendaylight.controller.md.sal.common.api.data.TransactionChainClosedException;
  21 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadTransaction;
  22 import org.opendaylight.controller.sal.core.spi.data.DOMStoreReadWriteTransaction;
  23 import org.opendaylight.controller.sal.core.spi.data.DOMStoreTransactionChain;
  24 import org.opendaylight.controller.sal.core.spi.data.DOMStoreWriteTransaction;
  25 import scala.concurrent.Future;
  26 import scala.concurrent.Promise;
  27
  28 /**
  29  * TransactionChainProxy acts as a proxy for a DOMStoreTransactionChain created on a remote shard
  30  */
  31 public class TransactionChainProxy implements DOMStoreTransactionChain {
  32     private interface State {
  33         boolean isReady();
  34
  35         SimpleEntry<Object, List<Future<ActorSelection>>> getReadyFutures();
  36
  37         void setReadyFutures(Object txIdentifier, List<Future<ActorSelection>> readyFutures);
  38     }
  39
  40     private static class Allocated implements State {
  41         private volatile SimpleEntry<Object, List<Future<ActorSelection>>> readyFutures;
  42
  43         @Override
  44         public boolean isReady() {
  45             return readyFutures != null;
  46         }
  47
  48         @Override
  49         public SimpleEntry<Object, List<Future<ActorSelection>>> getReadyFutures() {
  50             return readyFutures != null ? readyFutures : EMPTY_READY_FUTURES;
  51         }
  52
  53         @Override
  54         public void setReadyFutures(Object txIdentifier, List<Future<ActorSelection>> readyFutures) {
  55             this.readyFutures = new SimpleEntry<>(txIdentifier, readyFutures);
  56         }
  57     }
  58
  59     private static abstract class AbstractDefaultState implements State {
  60         @Override
  61         public SimpleEntry<Object, List<Future<ActorSelection>>> getReadyFutures() {
  62             return EMPTY_READY_FUTURES;
  63         }
  64
  65         @Override
  66         public void setReadyFutures(Object txIdentifier, List<Future<ActorSelection>> readyFutures) {
  67             throw new IllegalStateException("No transaction is allocated");
  68         }
  69     }
  70
  71     private static final State IDLE_STATE = new AbstractDefaultState() {
  72         @Override
  73         public boolean isReady() {
  74             return true;
  75         }
  76     };
  77
  78     private static final State CLOSED_STATE = new AbstractDefaultState() {
  79         @Override
  80         public boolean isReady() {
  81             throw new TransactionChainClosedException("Transaction chain has been closed");
  82         }
  83     };
  84
  85     private static final SimpleEntry<Object, List<Future<ActorSelection>>> EMPTY_READY_FUTURES =
  86             new SimpleEntry<Object, List<Future<ActorSelection>>>("",
  87                     Collections.<Future<ActorSelection>>emptyList());
  88
  89     private static final AtomicReferenceFieldUpdater<TransactionChainProxy, State> STATE_UPDATER =
  90             AtomicReferenceFieldUpdater.newUpdater(TransactionChainProxy.class, State.class, "state");
  91
  92     private final ActorContext actorContext;
  93     private final String transactionChainId;
  94     private volatile State state = IDLE_STATE;
  95
  96     public TransactionChainProxy(ActorContext actorContext) {
  97         this.actorContext = actorContext;
  98         transactionChainId = actorContext.getCurrentMemberName() + "-" + System.currentTimeMillis();
  99     }
 100
 101     @Override
 102     public DOMStoreReadTransaction newReadOnlyTransaction() {
 103         checkReadyState();
 104         return new ChainedTransactionProxy(actorContext, TransactionProxy.TransactionType.READ_ONLY);
 105     }
 106
 107     @Override
 108     public DOMStoreReadWriteTransaction newReadWriteTransaction() {
 109         return allocateWriteTransaction(TransactionProxy.TransactionType.READ_WRITE);
 110     }
 111
 112     @Override
 113     public DOMStoreWriteTransaction newWriteOnlyTransaction() {
 114         return allocateWriteTransaction(TransactionProxy.TransactionType.WRITE_ONLY);
 115     }
 116
 117     @Override
 118     public void close() {
 119         state = CLOSED_STATE;
 120
 121         // Send a close transaction chain request to each and every shard
 122         actorContext.broadcast(new CloseTransactionChain(transactionChainId));
 123     }
 124
 125     private ChainedTransactionProxy allocateWriteTransaction(TransactionProxy.TransactionType type) {
 126         checkReadyState();
 127
 128         ChainedTransactionProxy txProxy = new ChainedTransactionProxy(actorContext, type);
 129         STATE_UPDATER.compareAndSet(this, IDLE_STATE, new Allocated());
 130
 131         return txProxy;
 132     }
 133
 134     private void checkReadyState() {
 135         Preconditions.checkState(state.isReady(), "Previous transaction %s is not ready yet",
 136                 state.getReadyFutures().getKey());
 137     }
 138
 139     private class ChainedTransactionProxy extends TransactionProxy {
 140
 141         ChainedTransactionProxy(ActorContext actorContext, TransactionType transactionType) {
 142             super(actorContext, transactionType, transactionChainId);
 143         }
 144
 145         @Override
 146         protected void onTransactionReady(List<Future<ActorSelection>> readyFutures) {
 147             state.setReadyFutures(getIdentifier(), readyFutures);
 148         }
 149
 150         /**
 151          * This method is overridden to ensure the previous Tx's ready operations complete
 152          * before we create the next shard Tx in the chain to avoid creation failures if the
 153          * previous Tx's ready operations haven't completed yet.
 154          */
 155         @Override
 156         protected Future<Object> sendCreateTransaction(final ActorSelection shard,
 157                 final Object serializedCreateMessage) {
 158
 159             // Check if there are any previous ready Futures, otherwise let the super class handle it.
 160             // The second check is done to ensure the the previous ready Futures aren't for this
 161             // Tx instance as deadlock would occur if we tried to wait on our own Futures. This can
 162             // occur in this scenario:
 163             //
 164             //     - the TransactionProxy is created and the client does a write.
 165             //
 166             //     - the TransactionProxy then attempts to create the shard Tx. However it first
 167             //       sends a FindPrimaryShard message to the shard manager to find the local shard
 168             //       This call is done async.
 169             //
 170             //     - the client submits the Tx and the TransactionProxy is readied and we cache
 171             //       the ready Futures here.
 172             //
 173             //     - then the FindPrimaryShard call completes and this method is called to create
 174             //       the shard Tx. However the cached Futures were from the ready on this Tx. If we
 175             //       tried to wait on them, it would cause a form of deadlock as the ready Future
 176             //       would be waiting on the Tx create Future and vice versa.
 177             SimpleEntry<Object, List<Future<ActorSelection>>> readyFuturesEntry = state.getReadyFutures();
 178             List<Future<ActorSelection>> readyFutures = readyFuturesEntry.getValue();
 179             if(readyFutures.isEmpty() || getIdentifier().equals(readyFuturesEntry.getKey())) {
 180                 return super.sendCreateTransaction(shard, serializedCreateMessage);
 181             }
 182
 183             // Combine the ready Futures into 1.
 184             Future<Iterable<ActorSelection>> combinedFutures = akka.dispatch.Futures.sequence(
 185                     readyFutures, actorContext.getActorSystem().dispatcher());
 186
 187             // Add a callback for completion of the combined Futures.
 188             final Promise<Object> createTxPromise = akka.dispatch.Futures.promise();
 189             OnComplete<Iterable<ActorSelection>> onComplete = new OnComplete<Iterable<ActorSelection>>() {
 190                 @Override
 191                 public void onComplete(Throwable failure, Iterable<ActorSelection> notUsed) {
 192                     if(failure != null) {
 193                         // A Ready Future failed so fail the returned Promise.
 194                         createTxPromise.failure(failure);
 195                     } else {
 196                         // Send the CreateTx message and use the resulting Future to complete the
 197                         // returned Promise.
 198                         createTxPromise.completeWith(actorContext.executeOperationAsync(shard,
 199                                 serializedCreateMessage));
 200                     }
 201                 }
 202             };
 203
 204             combinedFutures.onComplete(onComplete, actorContext.getActorSystem().dispatcher());
 205
 206             return createTxPromise.future();
 207         }
 208     }
 209 }