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

   1 /*
   2  * Copyright (c) 2016 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 com.google.common.base.MoreObjects;
  11 import com.google.common.base.Preconditions;
  12 import com.google.common.base.Verify;
  13 import java.util.ArrayDeque;
  14 import java.util.Iterator;
  15 import java.util.Queue;
  16 import javax.annotation.Nullable;
  17 import javax.annotation.concurrent.NotThreadSafe;
  18 import org.opendaylight.controller.cluster.access.commands.OutOfOrderRequestException;
  19 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  20 import org.opendaylight.controller.cluster.access.commands.TransactionSuccess;
  21 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  22 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  23 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  24 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  25 import org.opendaylight.yangtools.concepts.Identifiable;
  26
  27 /**
  28  * Frontend common transaction state as observed by the shard leader.
  29  *
  30  * @author Robert Varga
  31  */
  32 @NotThreadSafe
  33 abstract class FrontendTransaction implements Identifiable<TransactionIdentifier> {
  34     private final AbstractFrontendHistory history;
  35     private final TransactionIdentifier id;
  36
  37     /**
  38      * It is possible that after we process a request and send a response that response gets lost and the client
  39      * initiates a retry. Since subsequent requests can mutate transaction state we need to retain the response until
  40      * it is acknowledged by the client.
  41      */
  42     private final Queue<Object> replayQueue = new ArrayDeque<>();
  43     private long firstReplaySequence;
  44     private Long lastPurgedSequence;
  45     private long expectedSequence;
  46
  47     FrontendTransaction(final AbstractFrontendHistory history, final TransactionIdentifier id) {
  48         this.history = Preconditions.checkNotNull(history);
  49         this.id = Preconditions.checkNotNull(id);
  50     }
  51
  52     @Override
  53     public final TransactionIdentifier getIdentifier() {
  54         return id;
  55     }
  56
  57     final AbstractFrontendHistory history() {
  58         return history;
  59     }
  60
  61     final java.util.Optional<TransactionSuccess<?>> replaySequence(final long sequence) throws RequestException {
  62         // Fast path check: if the requested sequence is the next request, bail early
  63         if (expectedSequence == sequence) {
  64             return java.util.Optional.empty();
  65         }
  66
  67         // Check sequencing: we do not need to bother with future requests
  68         if (Long.compareUnsigned(expectedSequence, sequence) < 0) {
  69             throw new OutOfOrderRequestException(expectedSequence);
  70         }
  71
  72         // Sanity check: if we have purged sequences, this has to be newer
  73         if (lastPurgedSequence != null && Long.compareUnsigned(lastPurgedSequence.longValue(), sequence) >= 0) {
  74             // Client has sent a request sequence, which has already been purged. This is a hard error, which should
  75             // never occur. Throwing an IllegalArgumentException will cause it to be wrapped in a
  76             // RuntimeRequestException (which is not retriable) and report it back to the client.
  77             throw new IllegalArgumentException(String.format("Invalid purged sequence %s (last purged is %s)",
  78                 sequence, lastPurgedSequence));
  79         }
  80
  81         // At this point we have established that the requested sequence lies in the open interval
  82         // (lastPurgedSequence, expectedSequence). That does not actually mean we have a response, as the commit
  83         // machinery is asynchronous, hence a reply may be in the works and not available.
  84
  85         long replaySequence = firstReplaySequence;
  86         final Iterator<?> it = replayQueue.iterator();
  87         while (it.hasNext()) {
  88             final Object replay = it.next();
  89             if (replaySequence == sequence) {
  90                 if (replay instanceof RequestException) {
  91                     throw (RequestException) replay;
  92                 }
  93
  94                 Verify.verify(replay instanceof TransactionSuccess);
  95                 return java.util.Optional.of((TransactionSuccess<?>) replay);
  96             }
  97
  98             replaySequence++;
  99         }
 100
 101         // Not found
 102         return java.util.Optional.empty();
 103     }
 104
 105     final void purgeSequencesUpTo(final long sequence) {
 106         // FIXME: implement this
 107
 108         lastPurgedSequence = sequence;
 109     }
 110
 111     // Sequence has already been checked
 112     abstract @Nullable TransactionSuccess<?> handleRequest(TransactionRequest<?> request,
 113             RequestEnvelope envelope, long now) throws RequestException;
 114
 115     private void recordResponse(final long sequence, final Object response) {
 116         if (replayQueue.isEmpty()) {
 117             firstReplaySequence = sequence;
 118         }
 119         replayQueue.add(response);
 120         expectedSequence++;
 121     }
 122
 123     final <T extends TransactionSuccess<?>> T recordSuccess(final long sequence, final T success) {
 124         recordResponse(sequence, success);
 125         return success;
 126     }
 127
 128     private long executionTime(final long startTime) {
 129         return history.readTime() - startTime;
 130     }
 131
 132     final void recordAndSendSuccess(final RequestEnvelope envelope, final long startTime,
 133             final TransactionSuccess<?> success) {
 134         recordResponse(success.getSequence(), success);
 135         envelope.sendSuccess(success, executionTime(startTime));
 136     }
 137
 138     final void recordAndSendFailure(final RequestEnvelope envelope, final long startTime,
 139             final RuntimeRequestException failure) {
 140         recordResponse(envelope.getMessage().getSequence(), failure);
 141         envelope.sendFailure(failure, executionTime(startTime));
 142     }
 143
 144     @Override
 145     public final String toString() {
 146         return MoreObjects.toStringHelper(this).omitNullValues().add("identifier", getIdentifier())
 147                 .add("expectedSequence", expectedSequence).add("firstReplaySequence", firstReplaySequence)
 148                 .add("lastPurgedSequence", lastPurgedSequence)
 149                 .toString();
 150     }
 151
 152 }