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Apache Geode provides a database-like consistency model, reliable transaction processing and a shared-nothing architecture to maintain very low latency performance with high concurrency processing

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package org.apache.geode.cache.wan;

import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.util.Arrays;

import org.apache.geode.distributed.internal.membership.InternalDistributedMember;

/**
 * This class wraps 1) DistributedMembershipID 2) ThreadID 3) SequenceID attributes which are used
 * to uniquely identify any Region Operation like create, update, destroy etc. This helps in
 * sequencing the events belonging to a unique producer. As an example, the EventSequenceID can be
 * used to track the events received by AsyncEventListener. If the event has already
 * been seen, AsyncEventListener can choose to ignore it.
 */
public final class EventSequenceID {
  /**
   * Uniquely identifies the distributed member VM in which the Event is produced
   */
  private String membershipID;

  /**
   * Unqiuely identifies the thread producing the event
   */
  private long threadID;

  /**
   * Uniquely identifies individual event produced by a given thread
   */
  private long sequenceID;

  public EventSequenceID(byte[] membershipID, long threadID, long sequenceID) {
    // convert the byte array of membershipID to a readable string
    Object mbr;
    try {
      mbr = InternalDistributedMember
          .readEssentialData(new DataInputStream(new ByteArrayInputStream(membershipID)));
    } catch (Exception e) {
      mbr = Arrays.toString(membershipID); // punt and use the bytes
    }
    this.membershipID = mbr.toString();
    this.threadID = threadID;
    this.sequenceID = sequenceID;
  }

  public String getMembershipID() {
    return this.membershipID;
  }

  public long getThreadID() {
    return this.threadID;
  }

  public long getSequenceID() {
    return this.sequenceID;
  }

  public boolean equals(Object obj) {
    if (!(obj instanceof EventSequenceID))
      return false;

    EventSequenceID obj2 = (EventSequenceID) obj;
    return (this.membershipID.equals(obj2.getMembershipID()) && this.threadID == obj2.getThreadID()
        && this.sequenceID == obj2.getSequenceID());
  }

  public int hashCode() {
    StringBuilder builder = new StringBuilder();
    builder.append(this.membershipID);
    builder.append(this.threadID);
    builder.append(this.sequenceID);
    return builder.toString().hashCode();
  }

  public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append("membershipID: " + membershipID);
    builder.append("; threadID: " + threadID);
    builder.append("; sequenceID: " + sequenceID);
    return builder.toString();
  }

}