content: /*
   * 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.cassandra.gms;
  
  import org.apache.cassandra.locator.InetAddressAndPort;
  
  /**
   * This is called by an instance of the IEndpointStateChangePublisher to notify
   * interested parties about changes in the the state associated with any endpoint.
   * For instance if node A figures there is a changes in state for an endpoint B
   * it notifies all interested parties of this change. It is upto to the registered
   * instance to decide what he does with this change. Not all modules maybe interested
   * in all state changes.
   */
  public interface IEndpointStateChangeSubscriber
  {
      /**
       * Use to inform interested parties about the change in the state
       * for specified endpoint
       *
       * @param endpoint endpoint for which the state change occurred.
       * @param epState  state that actually changed for the above endpoint.
       */
      default void onJoin(InetAddressAndPort endpoint, EndpointState epState) {}
      
      default void beforeChange(InetAddressAndPort endpoint, EndpointState currentState, ApplicationState newStateKey, VersionedValue newValue) {}
  
      default void onChange(InetAddressAndPort endpoint, ApplicationState state, VersionedValue value) {}
  
      default void onAlive(InetAddressAndPort endpoint, EndpointState state) {}
  
      default void onDead(InetAddressAndPort endpoint, EndpointState state) {}
  
      default void onRemove(InetAddressAndPort endpoint) {}
  
      /**
       * Called whenever a node is restarted.
       * Note that there is no guarantee when that happens that the node was
       * previously marked down. It will have only if {@code state.isAlive() == false}
       * as {@code state} is from before the restarted node is marked up.
       */
      default void onRestart(InetAddressAndPort endpoint, EndpointState state) {}
  }
  