hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/ha/SCMService.java

/**
 * 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
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * 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.hadoop.hdds.scm.ha;

/**
 * Interface for background services in SCM, including ReplicationManager,
 * SCMBlockDeletingService and BackgroundPipelineCreator.
 *
 * Provide a fine-grained method to manipulate the status of these background
 * services.
 */
public interface SCMService {
  /**
   * Notify raft or safe mode related status changed.
   */
  void notifyStatusChanged();

  /**
   * @param event latest triggered event.
   */
  default void notifyEventTriggered(Event event) {
  }

  /**
   * @return true, if next iteration of Service should take effect,
   *         false, if next iteration of Service should be skipped.
   */
  boolean shouldRun();

  /**
   * @return name of the Service.
   */
  String getServiceName();

  /**
   * Status of Service.
   */
  enum ServiceStatus {
    RUNNING,
    PAUSING
  }

  /**
   * One time event.
   */
  enum Event {
    PRE_CHECK_COMPLETED,
    NEW_NODE_HANDLER_TRIGGERED,
    NODE_ADDRESS_UPDATE_HANDLER_TRIGGERED,
    UNHEALTHY_TO_HEALTHY_NODE_HANDLER_TRIGGERED
  }

  /**
   * starts the SCM service.
   */
  void start() throws SCMServiceException;

  /**
   * stops the SCM service.
   */
  void stop();
}