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1   /**
2    * Copyright 2011 The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  package org.apache.hadoop.hbase.ipc;
21  
22  import java.io.IOException;
23  
24  /**
25   * A call whose response can be delayed by the server.
26   */
27  public interface Delayable {
28    /**
29     * Signal that the call response should be delayed, thus freeing the RPC
30     * server to handle different requests.
31     *
32     * @param delayReturnValue Controls whether the return value of the call
33     * should be set when ending the delay or right away.  There are cases when
34     * the return value can be set right away, even if the call is delayed.
35     */
36    public void startDelay(boolean delayReturnValue);
37  
38    /**
39     * @return is the call delayed?
40     */
41    public boolean isDelayed();
42  
43    /**
44     * @return is the return value delayed?
45     */
46    public boolean isReturnValueDelayed();
47  
48    /**
49     * Signal that the  RPC server is now allowed to send the response.
50     * @param result The value to return to the caller.  If the corresponding
51     * delay response specified that the return value should
52     * not be delayed, this parameter must be null.
53     * @throws IOException
54     */
55    public void endDelay(Object result) throws IOException;
56  
57    /**
58     * Signal the end of a delayed RPC, without specifying the return value.  Use
59     * this only if the return value was not delayed
60     * @throws IOException
61     */
62    public void endDelay() throws IOException;
63  
64    /**
65     * End the call, throwing and exception to the caller.  This works regardless
66     * of the return value being delayed.
67     * @param t Object to throw to the client.
68     * @throws IOException
69     */
70    public void endDelayThrowing(Throwable t) throws IOException;
71  }