Service.java

/**
 * Copyright 2016 LinkedIn Corp. Licensed 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.
 */
package com.linkedin.kmf.services;

/**
 * Services are components of a monitoring application that are expected to be running continuously in order to perform
 * monitoring.
 */
public interface Service {

  static final String JMX_PREFIX = "kmf.services";

  /**
   * The start logic must only execute once.  If an error occurs then the implementer of this class must assume that
   * stop() will be called to clean up.  This method must be thread safe and must assume that stop() may be called
   * concurrently. This can happen if the monitoring application's life cycle is being managed by a container.  Start
   * will only be called once.
   */
  void start();

  /**
   * This may be called multiple times.  This method must be thread safe and must assume that start() may be called
   * concurrently.  This can happen if the monitoring application's life cycle is being managed by a container.
   * Implementations must be non-blocking and should release the resources acquired by the service during start().
   */
  void stop();

  /**
   * Implementations of this method must be thread safe as it can be called at any time.  Implementations must be
   * non-blocking.
   * @return true if this start() has returned successfully else this must return false.  This must also return false if
   * the service can no longer perform its function.
   */
  boolean isRunning();

  /**
   * Implementations of this method must be thread safe and must be blocking.
   */
  void awaitShutdown();
}