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

   1 /*
   2  * Copyright (c) 2016, 2017 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 java.util.Objects.requireNonNull;
  11
  12 import com.google.common.base.MoreObjects;
  13 import com.google.common.base.Verify;
  14 import java.util.ArrayDeque;
  15 import java.util.Optional;
  16 import java.util.Queue;
  17 import org.eclipse.jdt.annotation.Nullable;
  18 import org.opendaylight.controller.cluster.access.commands.IncrementTransactionSequenceRequest;
  19 import org.opendaylight.controller.cluster.access.commands.IncrementTransactionSequenceSuccess;
  20 import org.opendaylight.controller.cluster.access.commands.OutOfOrderRequestException;
  21 import org.opendaylight.controller.cluster.access.commands.TransactionRequest;
  22 import org.opendaylight.controller.cluster.access.commands.TransactionSuccess;
  23 import org.opendaylight.controller.cluster.access.concepts.RequestEnvelope;
  24 import org.opendaylight.controller.cluster.access.concepts.RequestException;
  25 import org.opendaylight.controller.cluster.access.concepts.RuntimeRequestException;
  26 import org.opendaylight.controller.cluster.access.concepts.TransactionIdentifier;
  27 import org.opendaylight.yangtools.concepts.Identifiable;
  28 import org.slf4j.Logger;
  29 import org.slf4j.LoggerFactory;
  30
  31 /**
  32  * Frontend common transaction state as observed by the shard leader. This class is NOT thread-safe.
  33  *
  34  * @author Robert Varga
  35  */
  36 abstract class FrontendTransaction implements Identifiable<TransactionIdentifier> {
  37     private static final Logger LOG = LoggerFactory.getLogger(FrontendTransaction.class);
  38
  39     private final AbstractFrontendHistory history;
  40     private final TransactionIdentifier id;
  41
  42     /**
  43      * It is possible that after we process a request and send a response that response gets lost and the client
  44      * initiates a retry. Since subsequent requests can mutate transaction state we need to retain the response until
  45      * it is acknowledged by the client.
  46      */
  47     private final Queue<Object> replayQueue = new ArrayDeque<>();
  48     private long firstReplaySequence;
  49     private Long lastPurgedSequence;
  50     private long expectedSequence;
  51
  52     private RequestException previousFailure;
  53
  54     FrontendTransaction(final AbstractFrontendHistory history, final TransactionIdentifier id) {
  55         this.history = requireNonNull(history);
  56         this.id = requireNonNull(id);
  57     }
  58
  59     @Override
  60     public final TransactionIdentifier getIdentifier() {
  61         return id;
  62     }
  63
  64     final AbstractFrontendHistory history() {
  65         return history;
  66     }
  67
  68     final String persistenceId() {
  69         return history().persistenceId();
  70     }
  71
  72     final Optional<TransactionSuccess<?>> replaySequence(final long sequence) throws RequestException {
  73         // Fast path check: if the requested sequence is the next request, bail early
  74         if (expectedSequence == sequence) {
  75             return Optional.empty();
  76         }
  77
  78         // Check sequencing: we do not need to bother with future requests
  79         if (Long.compareUnsigned(expectedSequence, sequence) < 0) {
  80             throw new OutOfOrderRequestException(expectedSequence);
  81         }
  82
  83         // Sanity check: if we have purged sequences, this has to be newer
  84         if (lastPurgedSequence != null && Long.compareUnsigned(lastPurgedSequence.longValue(), sequence) >= 0) {
  85             // Client has sent a request sequence, which has already been purged. This is a hard error, which should
  86             // never occur. Throwing an IllegalArgumentException will cause it to be wrapped in a
  87             // RuntimeRequestException (which is not retriable) and report it back to the client.
  88             throw new IllegalArgumentException(String.format("Invalid purged sequence %s (last purged is %s)",
  89                 sequence, lastPurgedSequence));
  90         }
  91
  92         // At this point we have established that the requested sequence lies in the open interval
  93         // (lastPurgedSequence, expectedSequence). That does not actually mean we have a response, as the commit
  94         // machinery is asynchronous, hence a reply may be in the works and not available.
  95
  96         long replaySequence = firstReplaySequence;
  97         for (Object replay : replayQueue) {
  98             if (replaySequence == sequence) {
  99                 if (replay instanceof RequestException) {
 100                     throw (RequestException) replay;
 101                 }
 102
 103                 Verify.verify(replay instanceof TransactionSuccess);
 104                 return Optional.of((TransactionSuccess<?>) replay);
 105             }
 106
 107             replaySequence++;
 108         }
 109
 110         // Not found
 111         return Optional.empty();
 112     }
 113
 114     final void purgeSequencesUpTo(final long sequence) {
 115         // FIXME: implement this
 116
 117         lastPurgedSequence = sequence;
 118     }
 119
 120     // Request order has already been checked by caller and replaySequence()
 121     @SuppressWarnings("checkstyle:IllegalCatch")
 122     final @Nullable TransactionSuccess<?> handleRequest(final TransactionRequest<?> request,
 123             final RequestEnvelope envelope, final long now) throws RequestException {
 124         if (request instanceof IncrementTransactionSequenceRequest) {
 125             final IncrementTransactionSequenceRequest incr = (IncrementTransactionSequenceRequest) request;
 126             expectedSequence += incr.getIncrement();
 127
 128             return recordSuccess(incr.getSequence(),
 129                     new IncrementTransactionSequenceSuccess(incr.getTarget(), incr.getSequence()));
 130         }
 131
 132         if (previousFailure != null) {
 133             LOG.debug("{}: Rejecting request {} due to previous failure", persistenceId(), request, previousFailure);
 134             throw previousFailure;
 135         }
 136
 137         try {
 138             return doHandleRequest(request, envelope, now);
 139         } catch (RuntimeException e) {
 140             /*
 141              * The request failed to process, we should not attempt to ever
 142              * apply it again. Furthermore we cannot accept any further requests
 143              * from this connection, simply because the transaction state is
 144              * undefined.
 145              */
 146             LOG.debug("{}: Request {} failed to process", persistenceId(), request, e);
 147             previousFailure = new RuntimeRequestException("Request " + request + " failed to process", e);
 148             throw previousFailure;
 149         }
 150     }
 151
 152     abstract @Nullable TransactionSuccess<?> doHandleRequest(TransactionRequest<?> request, RequestEnvelope envelope,
 153             long now) throws RequestException;
 154
 155     abstract void retire();
 156
 157     private void recordResponse(final long sequence, final Object response) {
 158         if (replayQueue.isEmpty()) {
 159             firstReplaySequence = sequence;
 160         }
 161         replayQueue.add(response);
 162         expectedSequence++;
 163     }
 164
 165     final <T extends TransactionSuccess<?>> T recordSuccess(final long sequence, final T success) {
 166         recordResponse(sequence, success);
 167         return success;
 168     }
 169
 170     private long executionTime(final long startTime) {
 171         return history.readTime() - startTime;
 172     }
 173
 174     final void recordAndSendSuccess(final RequestEnvelope envelope, final long startTime,
 175             final TransactionSuccess<?> success) {
 176         recordResponse(success.getSequence(), success);
 177         envelope.sendSuccess(success, executionTime(startTime));
 178     }
 179
 180     final void recordAndSendFailure(final RequestEnvelope envelope, final long startTime,
 181             final RuntimeRequestException failure) {
 182         recordResponse(envelope.getMessage().getSequence(), failure);
 183         envelope.sendFailure(failure, executionTime(startTime));
 184     }
 185
 186     @Override
 187     public final String toString() {
 188         return MoreObjects.toStringHelper(this).omitNullValues().add("identifier", getIdentifier())
 189                 .add("expectedSequence", expectedSequence).add("firstReplaySequence", firstReplaySequence)
 190                 .add("lastPurgedSequence", lastPurgedSequence)
 191                 .toString();
 192     }
 193 }