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