1 /**
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 */
18 package org.apache.hadoop.hbase.errorhandling;
19
20 import org.apache.hadoop.hbase.classification.InterfaceAudience;
21
22 /**
23 * This is an interface for a cooperative exception throwing mechanism. Implementations are
24 * containers that holds an exception from a separate thread. This can be used to receive
25 * exceptions from 'foreign' threads or from separate 'foreign' processes.
26 * <p>
27 * To use, one would pass an implementation of this object to a long running method and
28 * periodically check by calling {@link #rethrowException()}. If any foreign exceptions have
29 * been received, the calling thread is then responsible for handling the rethrown exception.
30 * <p>
31 * One could use the boolean {@link #hasException()} to determine if there is an exceptoin as well.
32 * <p>
33 * NOTE: This is very similar to the InterruptedException/interrupt/interrupted pattern. There,
34 * the notification state is bound to a Thread. Using this, applications receive Exceptions in
35 * the snare. The snare is referenced and checked by multiple threads which enables exception
36 * notification in all the involved threads/processes.
37 */
38 @InterfaceAudience.Private
39 public interface ForeignExceptionSnare {
40
41 /**
42 * Rethrow an exception currently held by the {@link ForeignExceptionSnare}. If there is
43 * no exception this is a no-op
44 *
45 * @throws ForeignException
46 * all exceptions from remote sources are procedure exceptions
47 */
48 void rethrowException() throws ForeignException;
49
50 /**
51 * Non-exceptional form of {@link #rethrowException()}. Checks to see if any
52 * process to which the exception checkers is bound has created an error that
53 * would cause a failure.
54 *
55 * @return <tt>true</tt> if there has been an error,<tt>false</tt> otherwise
56 */
57 boolean hasException();
58
59 /**
60 * Get the value of the captured exception.
61 *
62 * @return the captured foreign exception or null if no exception captured.
63 */
64 ForeignException getException();
65 }