1   /*
2    * Copyright 2019 LINE Corporation
3    *
4    * LINE Corporation licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package com.linecorp.centraldogma.server.plugin;
17  
18  import java.util.concurrent.CompletionStage;
19  
20  import com.linecorp.centraldogma.server.CentralDogmaConfig;
21  
22  /**
23   * An interface which defines callbacks for a plug-in. If you want to initialize a {@link Plugin} by configuring
24   * the Central Dogma server (e.g. adding a service for your plugin), use {@link AllReplicasPlugin}.
25   */
26  public interface Plugin {
27      /**
28       * Returns the {@link PluginTarget} which specifies the replicas that this {@link Plugin} is applied to.
29       */
30      PluginTarget target(CentralDogmaConfig config);
31  
32      /**
33       * Invoked when this {@link Plugin} is supposed to be started.
34       *
35       * @param context the context which consists of the objects required to execute this {@link Plugin}
36       */
37      CompletionStage<Void> start(PluginContext context);
38  
39      /**
40       * Invoked when this {@link Plugin} is supposed to be stopped.
41       *
42       * @param context the context which consists of the objects required to execute this {@link Plugin}
43       */
44      CompletionStage<Void> stop(PluginContext context);
45  
46      /**
47       * Returns {@code true} if this {@link Plugin} is enabled.
48       */
49      default boolean isEnabled(CentralDogmaConfig config) {
50          final PluginConfig pluginConfig = config.pluginConfigMap().get(configType());
51          if (pluginConfig == null) {
52              // Enabled if not found.
53              return true;
54          }
55          return pluginConfig.enabled();
56      }
57  
58      /**
59       * Returns the type of the configuration for this {@link Plugin}.
60       */
61      Class<?> configType();
62  }