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.classification.InterfaceAudience; 21 import org.apache.hadoop.classification.InterfaceStability; 22 23 /** 24 * This is an interface for a cooperative exception throwing mechanism. Implementations are 25 * containers that holds an exception from a separate thread. This can be used to receive 26 * exceptions from 'foreign' threads or from separate 'foreign' processes. 27 * <p> 28 * To use, one would pass an implementation of this object to a long running method and 29 * periodically check by calling {@link #rethrowException()}. If any foreign exceptions have 30 * been received, the calling thread is then responsible for handling the rethrown exception. 31 * <p> 32 * One could use the boolean {@link #hasException()} to determine if there is an exceptoin as well. 33 * <p> 34 * NOTE: This is very similar to the InterruptedException/interrupt/interrupted pattern. There, 35 * the notification state is bound to a Thread. Using this, applications receive Exceptions in 36 * the snare. The snare is referenced and checked by multiple threads which enables exception 37 * notification in all the involved threads/processes. 38 */ 39 @InterfaceAudience.Public 40 @InterfaceStability.Evolving 41 public interface ForeignExceptionSnare { 42 43 /** 44 * Rethrow an exception currently held by the {@link ForeignExceptionSnare}. If there is 45 * no exception this is a no-op 46 * 47 * @throws ForeignException 48 * all exceptions from remote sources are procedure exceptions 49 */ 50 public void rethrowException() throws ForeignException; 51 52 /** 53 * Non-exceptional form of {@link #rethrowException()}. Checks to see if any 54 * process to which the exception checkers is bound has created an error that 55 * would cause a failure. 56 * 57 * @return <tt>true</tt> if there has been an error,<tt>false</tt> otherwise 58 */ 59 public boolean hasException(); 60 61 /** 62 * Get the value of the captured exception. 63 * 64 * @return the captured foreign exception or null if no exception captured. 65 */ 66 public ForeignException getException(); 67 }