Esempio n. 1
0
  private KvReply perform(KvOperation operation) {
    final int MAX_ITERATIONS = 10000;
    KvReply reply = new KvReply();
    for (int i = 0; i < MAX_ITERATIONS; i++) {
      // So it have been processed yet, do not advance to make
      // at-most-once semantic
      String last = lastOperationUUID.get(operation.clientId);
      if (last != null && last.compareTo(operation.uuid) == 0) {
        reply.status = KvReply.Status.Success;
        reply.payload = lastOperation.get(operation.clientId);
        return reply;
      }

      int instanceId = completedOperationId + 1;
      Paxos.Status status = paxos.getStatus(instanceId);
      KvOperation result = null;

      if (status.accepted) {
        result = (KvOperation) status.value;
      } else {
        paxos.start(instanceId, operation);
        result = waitAgreement(instanceId);
        // If empty, please skip the apply operation
        if (result == null) continue;
      }
      // Apply (result, instanceId);
      apply(instanceId, result);
      if (operation.uuid.compareTo(result.uuid) == 0) {
        reply.status = KvReply.Status.Success;
        reply.payload = lastOperation.get(operation.clientId);
        return reply;
      }
    }
    reply.status = KvReply.Status.InternalError;
    return reply;
  }
Esempio n. 2
0
  private void apply(int instanceId, KvOperation operation) {
    if (engineInstance.containsKey(operation.key)) {
      lastOperation.put(operation.clientId, engineInstance.get(operation.key));
    } else {
      lastOperation.put(operation.clientId, null);
    }

    lastOperationUUID.put(operation.clientId, operation.uuid);

    if (operation.command == KvOperation.Command.PutOperation) {
      engineInstance.put(operation.key, operation.value);
    }

    completedOperationId++;
    paxos.done(instanceId);
  }