001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *   http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing,
013 * software distributed under the License is distributed on an
014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 * KIND, either express or implied.  See the License for the
016 * specific language governing permissions and limitations
017 * under the License.
018 */
019package org.apache.reef.driver.context;
020
021import org.apache.reef.annotations.Provided;
022import org.apache.reef.annotations.audience.DriverSide;
023import org.apache.reef.annotations.audience.Public;
024import org.apache.reef.io.Message;
025import org.apache.reef.io.Numberable;
026import org.apache.reef.io.naming.Identifiable;
027
028/**
029 * Driver-side representation of a message sent by a Context to the Driver.
030 */
031@Public
032@DriverSide
033@Provided
034public interface ContextMessage extends Message, Identifiable, Numberable {
035
036  /**
037   * @return the message sent by the Context.
038   */
039  @Override
040  byte[] get();
041
042  /**
043   * @return the ID of the sending Context.
044   */
045  @Override
046  String getId();
047
048  /**
049   * @return the ID of the ContextMessageSource that sent the message on the Context.
050   */
051  String getMessageSourceID();
052
053  /**
054   * @return the sequence number of the message
055   *
056   * Terminology: a source sends a message to a target.
057   * Example sources are Tasks or Contexts. Example targets are Drivers.
058   *
059   * The method guarantees that sequence numbers increase strictly monotonically per message source.
060   * So numbers of messages from different sources should not be compared to each other.
061   *
062   * Clients of this method must not assume any particular method implementation
063   * because it may change in the future.
064   *
065   * The current implementation returns the timestamp of a heartbeat that contained the message.
066   * A heartbeat may contain several messages; all such message will get the same sequence number.
067   * A source can attach only one message to a single heartbeat, so the strict sequence number monotonicity
068   * per source is guaranteed.
069   *
070   */
071  @Override
072  long getSequenceNumber();
073
074}