Java Code Examples for org.apache.accumulo.core.data.ConditionalMutation#put()

/**
 * Creates a {@link ConditionalMutation} that only updates the cardinality
 * of the PCJ table if the old value has not changed by the time this mutation
 * is committed to Accumulo.
 *
 * @param current - The current cardinality value.
 * @param delta - How much the cardinality will change.
 * @return The mutation that will perform the conditional update.
 */
private static ConditionalMutation makeUpdateCardinalityMutation(final long current, final long delta) {
    // Try to update the cardinality by the delta.
    final ConditionalMutation mutation = new ConditionalMutation(PCJ_METADATA_ROW_ID);
    final Condition lastCardinalityStillCurrent = new Condition(
            PCJ_METADATA_FAMILY,
            PCJ_METADATA_CARDINALITY);

    // Require the old cardinality to be the value we just read.
    final byte[] currentCardinalityBytes = longLexicoder.encode( current );
    lastCardinalityStillCurrent.setValue( currentCardinalityBytes );
    mutation.addCondition(lastCardinalityStillCurrent);

    // If that is the case, then update to the new value.
    final Value newCardinality = new Value( longLexicoder.encode(current + delta) );
    mutation.put(PCJ_METADATA_FAMILY, PCJ_METADATA_CARDINALITY, newCardinality);
    return mutation;
}
 

public void cancel(String what, String when, String who) throws Exception {

    String row = what + ":" + when;

    // Even though this method is only deleting a column, its important to use a conditional writer.
    // By updating the seq # when deleting a reservation, it
    // will cause any concurrent reservations to retry. If this delete were done using a batch
    // writer, then a concurrent reservation could report WAIT_LISTED
    // when it actually got the reservation.

    // its important to use an isolated scanner so that only whole mutations are seen
    try (
        ConditionalWriter cwriter = client.createConditionalWriter(rTable,
            new ConditionalWriterConfig());
        Scanner scanner = new IsolatedScanner(client.createScanner(rTable, Authorizations.EMPTY))) {
      while (true) {
        scanner.setRange(new Range(row));

        int seq = -1;
        String reservation = null;

        for (Entry<Key,Value> entry : scanner) {
          String cf = entry.getKey().getColumnFamilyData().toString();
          String cq = entry.getKey().getColumnQualifierData().toString();
          String val = entry.getValue().toString();

          // EXCERCISE avoid linear scan

          if (cf.equals("tx") && cq.equals("seq")) {
            seq = Integer.parseInt(val);
          } else if (cf.equals("res") && val.equals(who)) {
            reservation = cq;
          }
        }

        if (reservation != null) {
          ConditionalMutation update = new ConditionalMutation(row,
              new Condition("tx", "seq").setValue(seq + ""));
          update.putDelete("res", reservation);
          update.put("tx", "seq", (seq + 1) + "");

          Status status = cwriter.write(update).getStatus();
          switch (status) {
            case ACCEPTED:
              // successfully canceled reservation
              return;
            case REJECTED:
            case UNKNOWN:
              // retry
              // EXCERCISE exponential back-off could be used here
              break;
            default:
              throw new RuntimeException("Unexpected status " + status);
          }

        } else {
          // not reserved, nothing to do
          break;
        }

      }
    }
  }
 

@Override
public void update(final RyaDetails oldDetails, final RyaDetails newDetails)
        throws NotInitializedException, ConcurrentUpdateException, RyaDetailsRepositoryException {
    // Preconditions.
    requireNonNull(oldDetails);
    requireNonNull(newDetails);

    if(!newDetails.getRyaInstanceName().equals( instanceName )) {
        throw new RyaDetailsRepositoryException("The instance name that was in the provided 'newDetails' does not match " +
                "the instance name that this repository is connected to. Make sure you're connected to the" +
                "correct Rya instance.");
    }

    if(!isInitialized()) {
        throw new NotInitializedException("Could not update the details for the Rya instanced named '" +
                instanceName + "' because it has not been initialized yet.");
    }

    // Use a conditional writer so that we can detect when the old details
    // are no longer the currently stored ones.
    ConditionalWriter writer = null;
    try {
        // Setup the condition that ensures the details have not changed since the edits were made.
        final byte[] oldDetailsBytes = serializer.serialize(oldDetails);
        final Condition condition = new Condition(COL_FAMILY, COL_QUALIFIER);
        condition.setValue( oldDetailsBytes );

        // Create the mutation that only performs the update if the details haven't changed.
        final ConditionalMutation mutation = new ConditionalMutation(ROW_ID);
        mutation.addCondition( condition );
        final byte[] newDetailsBytes = serializer.serialize(newDetails);
        mutation.put(COL_FAMILY, COL_QUALIFIER, new Value(newDetailsBytes));

        // Do the write.
        writer = connector.createConditionalWriter(detailsTableName, new ConditionalWriterConfig());
        final Result result = writer.write(mutation);
        switch(result.getStatus()) {
            case REJECTED:
            case VIOLATED:
                throw new ConcurrentUpdateException("Could not update the details for the Rya instance named '" +
                        instanceName + "' because the old value is out of date.");
            case UNKNOWN:
            case INVISIBLE_VISIBILITY:
                throw new RyaDetailsRepositoryException("Could not update the details for the Rya instance named '" + instanceName + "'.");
        }
    } catch (final TableNotFoundException | AccumuloException | AccumuloSecurityException e) {
        throw new RyaDetailsRepositoryException("Could not update the details for the Rya instance named '" + instanceName + "'.");
    } finally {
        if(writer != null) {
            writer.close();
        }
    }
}