/**
 * 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.atlas.listener;

import org.apache.atlas.AtlasException;

/**
 * An interface that should be implemented by objects and services to react to changes in state of an Atlas server.
 *
 * The two state transitions we handle are (1) becoming active and (2) becoming passive.
 */
public interface ActiveStateChangeHandler {

    /**
     * Callback that is invoked on an implementor when this instance of Atlas server is declared the leader.
     *
     * Any initialization that must be carried out by an implementor only when the server becomes active
     * should happen on this callback.
     *
     * @throws {@link AtlasException} if anything is wrong on initialization
     */
    void instanceIsActive() throws AtlasException;

    /**
     * Callback that is invoked on an implementor when this instance of Atlas server is removed as the leader.
     *
     * Any cleanup that must be carried out by an implementor when the server becomes passive
     * should happen on this callback.
     *
     * @throws {@link AtlasException} if anything is wrong on shutdown
     */
    void instanceIsPassive() throws AtlasException;
}