| /** |
| * 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 { |
| public enum HandlerOrder { |
| HBASE_AUDIT_REPOSITORY(0), |
| GRAPH_BACKED_SEARCH_INDEXER(1), |
| TYPEDEF_STORE_INITIALIZER(2), |
| DEFAULT_METADATA_SERVICE(3), |
| NOTIFICATION_HOOK_CONSUMER(4); |
| |
| |
| private final int order; |
| |
| private HandlerOrder(int order) { |
| this.order = order; |
| } |
| |
| public int getOrder() { return order; } |
| } |
| |
| /** |
| * 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; |
| |
| |
| /** |
| * Defines the order in which the handler should be called. |
| * When state becomes active, the handler will be called from low order to high |
| * When state becomes passive, the handler will be called from high order to low |
| * |
| */ |
| int getHandlerOrder(); |
| } |