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1   /*
2    * Copyright 2015 The Netty Project
3    *
4    * The Netty Project 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    *   http://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 io.netty.channel.pool;
17  
18  import io.netty.channel.Channel;
19  import io.netty.channel.EventLoop;
20  import io.netty.util.concurrent.Future;
21  import io.netty.util.concurrent.Promise;
22  
23  /**
24   * Called before a {@link Channel} will be returned via {@link ChannelPool#acquire()} or
25   * {@link ChannelPool#acquire(Promise)}.
26   */
27  public interface ChannelHealthChecker {
28  
29      /**
30       * {@link ChannelHealthChecker} implementation that checks if {@link Channel#isActive()} returns {@code true}.
31       */
32      ChannelHealthChecker ACTIVE = new ChannelHealthChecker() {
33          @Override
34          public Future<Boolean> isHealthy(Channel channel) {
35              EventLoop loop = channel.eventLoop();
36              return channel.isActive()? loop.newSucceededFuture(Boolean.TRUE) : loop.newSucceededFuture(Boolean.FALSE);
37          }
38      };
39  
40      /**
41       * Check if the given channel is healthy which means it can be used. The returned {@link Future} is notified once
42       * the check is complete. If notified with {@link Boolean#TRUE} it can be used {@link Boolean#FALSE} otherwise.
43       *
44       * This method will be called by the {@link EventLoop} of the {@link Channel}.
45       */
46      Future<Boolean> isHealthy(Channel channel);
47  }