001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase.ipc; 019 020import com.google.protobuf.RpcCallback; 021import com.google.protobuf.RpcController; 022import java.io.IOException; 023import org.apache.hadoop.util.StringUtils; 024import org.apache.yetus.audience.InterfaceAudience; 025 026/** 027 * Used for server-side protobuf RPC service invocations. This handler allows invocation exceptions 028 * to easily be passed through to the RPC server from coprocessor 029 * {@link com.google.protobuf.Service} implementations. 030 * <p> 031 * When implementing {@link com.google.protobuf.Service} defined methods, coprocessor endpoints can 032 * use the following pattern to pass exceptions back to the RPC client: <code> 033 * public void myMethod(RpcController controller, MyRequest request, 034 * RpcCallback<MyResponse> done) { 035 * MyResponse response = null; 036 * try { 037 * // do processing 038 * response = MyResponse.getDefaultInstance(); // or use a new builder to populate the response 039 * } catch (IOException ioe) { 040 * // pass exception back up 041 * ResponseConverter.setControllerException(controller, ioe); 042 * } 043 * done.run(response); 044 * } 045 * </code> 046 * </p> 047 */ 048@InterfaceAudience.Private 049public class ServerRpcController implements RpcController { 050 /** 051 * The exception thrown within 052 * {@link com.google.protobuf.Service#callMethod(com.google.protobuf.Descriptors.MethodDescriptor, RpcController, com.google.protobuf.Message, RpcCallback)} 053 * if any. 054 */ 055 // TODO: it would be good widen this to just Throwable, but IOException is what we allow now 056 private IOException serviceException; 057 private String errorMessage; 058 059 @Override 060 public void reset() { 061 serviceException = null; 062 errorMessage = null; 063 } 064 065 @Override 066 public boolean failed() { 067 return (failedOnException() || errorMessage != null); 068 } 069 070 @Override 071 public String errorText() { 072 return errorMessage; 073 } 074 075 @Override 076 public void startCancel() { 077 // not implemented 078 } 079 080 @Override 081 public void setFailed(String message) { 082 errorMessage = message; 083 } 084 085 @Override 086 public boolean isCanceled() { 087 return false; 088 } 089 090 @Override 091 public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) { 092 // not implemented 093 } 094 095 /** 096 * Sets an exception to be communicated back to the {@link com.google.protobuf.Service} client. 097 * @param ioe the exception encountered during execution of the service method 098 */ 099 public void setFailedOn(IOException ioe) { 100 serviceException = ioe; 101 setFailed(StringUtils.stringifyException(ioe)); 102 } 103 104 /** 105 * Returns any exception thrown during service method invocation, or {@code null} if no exception 106 * was thrown. This can be used by clients to receive exceptions generated by RPC calls, even when 107 * {@link RpcCallback}s are used and no {@link com.google.protobuf.ServiceException} is declared. 108 */ 109 public IOException getFailedOn() { 110 return serviceException; 111 } 112 113 /** 114 * Returns whether or not a server exception was generated in the prior RPC invocation. 115 */ 116 public boolean failedOnException() { 117 return serviceException != null; 118 } 119 120 /** 121 * Throws an IOException back out if one is currently stored. 122 */ 123 public void checkFailed() throws IOException { 124 if (failedOnException()) { 125 throw getFailedOn(); 126 } 127 } 128}