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 }