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 19 package org.apache.hadoop.hbase.ipc; 20 21 import com.google.protobuf.Descriptors; 22 import com.google.protobuf.Message; 23 import com.google.protobuf.RpcCallback; 24 import com.google.protobuf.RpcController; 25 import com.google.protobuf.Service; 26 import org.apache.hadoop.util.StringUtils; 27 28 import java.io.IOException; 29 30 /** 31 * Used for server-side protobuf RPC service invocations. This handler allows 32 * invocation exceptions to easily be passed through to the RPC server from coprocessor 33 * {@link Service} implementations. 34 * 35 * <p> 36 * When implementing {@link Service} defined methods, coprocessor endpoints can use the following 37 * pattern to pass exceptions back to the RPC client: 38 * <code> 39 * public void myMethod(RpcController controller, MyRequest request, RpcCallback<MyResponse> done) { 40 * MyResponse response = null; 41 * try { 42 * // do processing 43 * response = MyResponse.getDefaultInstance(); // or use a new builder to populate the response 44 * } catch (IOException ioe) { 45 * // pass exception back up 46 * ResponseConverter.setControllerException(controller, ioe); 47 * } 48 * done.run(response); 49 * } 50 * </code> 51 * </p> 52 */ 53 public class ServerRpcController implements RpcController { 54 /** 55 * The exception thrown within 56 * {@link Service#callMethod(Descriptors.MethodDescriptor, RpcController, Message, RpcCallback)}, 57 * if any. 58 */ 59 // TODO: it would be good widen this to just Throwable, but IOException is what we allow now 60 private IOException serviceException; 61 private String errorMessage; 62 63 @Override 64 public void reset() { 65 serviceException = null; 66 errorMessage = null; 67 } 68 69 @Override 70 public boolean failed() { 71 return (failedOnException() || errorMessage != null); 72 } 73 74 @Override 75 public String errorText() { 76 return errorMessage; 77 } 78 79 @Override 80 public void startCancel() { 81 // not implemented 82 } 83 84 @Override 85 public void setFailed(String message) { 86 errorMessage = message; 87 } 88 89 @Override 90 public boolean isCanceled() { 91 return false; 92 } 93 94 @Override 95 public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) { 96 // not implemented 97 } 98 99 /** 100 * Sets an exception to be communicated back to the {@link Service} client. 101 * @param ioe the exception encountered during execution of the service method 102 */ 103 public void setFailedOn(IOException ioe) { 104 serviceException = ioe; 105 setFailed(StringUtils.stringifyException(ioe)); 106 } 107 108 /** 109 * Returns any exception thrown during service method invocation, or {@code null} if no exception 110 * was thrown. This can be used by clients to receive exceptions generated by RPC calls, even 111 * when {@link RpcCallback}s are used and no {@link com.google.protobuf.ServiceException} is 112 * declared. 113 */ 114 public IOException getFailedOn() { 115 return serviceException; 116 } 117 118 /** 119 * Returns whether or not a server exception was generated in the prior RPC invocation. 120 */ 121 public boolean failedOnException() { 122 return serviceException != null; 123 } 124 125 /** 126 * Throws an IOException back out if one is currently stored. 127 */ 128 public void checkFailed() throws IOException { 129 if (failedOnException()) { 130 throw getFailedOn(); 131 } 132 } 133 }