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1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one
4    * or more contributor license agreements.  See the NOTICE file
5    * distributed with this work for additional information
6    * regarding copyright ownership.  The ASF licenses this file
7    * to you under the Apache License, Version 2.0 (the
8    * "License"); you may not use this file except in compliance
9    * with the License.  You may obtain a copy of the License at
10   *
11   *     http://www.apache.org/licenses/LICENSE-2.0
12   *
13   * Unless required by applicable law or agreed to in writing, software
14   * distributed under the License is distributed on an "AS IS" BASIS,
15   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16   * See the License for the specific language governing permissions and
17   * limitations under the License.
18   */
19  
20  package org.apache.hadoop.hbase.client;
21  
22  import java.io.IOException;
23  
24  import org.apache.hadoop.hbase.classification.InterfaceAudience;
25  
26  /**
27   * A Callable<T> that will be retried.  If {@link #call(int)} invocation throws exceptions,
28   * we will call {@link #throwable(Throwable, boolean)} with whatever the exception was.
29   * @param <T> result class from executing <tt>this</tt>
30   */
31  @InterfaceAudience.Private
32  public interface RetryingCallable<T> {
33    /**
34     * Prepare by setting up any connections to servers, etc., ahead of {@link #call(int)} invocation.
35     * @param reload Set this to true if need to requery locations
36     * @throws IOException e
37     */
38    void prepare(final boolean reload) throws IOException;
39  
40    /**
41     * Called when {@link #call(int)} throws an exception and we are going to retry; take action to
42     * make it so we succeed on next call (clear caches, do relookup of locations, etc.).
43     * @param t
44     * @param retrying True if we are in retrying mode (we are not in retrying mode when max
45     * retries == 1; we ARE in retrying mode if retries &gt; 1 even when we are the last attempt)
46     */
47    void throwable(final Throwable t, boolean retrying);
48  
49    /**
50     * Computes a result, or throws an exception if unable to do so.
51     *
52     * @param callTimeout - the time available for this call. 0 for infinite.
53     * @return computed result
54     * @throws Exception if unable to compute a result
55     */
56    T call(int callTimeout) throws Exception;
57  
58    /**
59     * @return Some details from the implementation that we would like to add to a terminating
60     * exception; i.e. a fatal exception is being thrown ending retries and we might like to add
61     * more implementation-specific detail on to the exception being thrown.
62     */
63    String getExceptionMessageAdditionalDetail();
64  
65    /**
66     * @param pause
67     * @param tries
68     * @return Suggestion on how much to sleep between retries
69     */
70    long sleep(final long pause, final int tries);
71  }