View Javadoc

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  
27  import org.apache.hadoop.hbase.classification.InterfaceAudience;
28  import org.apache.hadoop.util.StringUtils;
29  
30  import java.io.IOException;
31  
32  /**
33   * Used for server-side protobuf RPC service invocations.  This handler allows
34   * invocation exceptions to easily be passed through to the RPC server from coprocessor
35   * {@link Service} implementations.
36   *
37   * <p>
38   * When implementing {@link Service} defined methods, coprocessor endpoints can use the following
39   * pattern to pass exceptions back to the RPC client:
40   * <code>
41   * public void myMethod(RpcController controller, MyRequest request, RpcCallback<MyResponse> done) {
42   *   MyResponse response = null;
43   *   try {
44   *     // do processing
45   *     response = MyResponse.getDefaultInstance();  // or use a new builder to populate the response
46   *   } catch (IOException ioe) {
47   *     // pass exception back up
48   *     ResponseConverter.setControllerException(controller, ioe);
49   *   }
50   *   done.run(response);
51   * }
52   * </code>
53   * </p>
54   */
55  @InterfaceAudience.Private
56  public class ServerRpcController implements RpcController {
57    /**
58     * The exception thrown within
59     * {@link Service#callMethod(Descriptors.MethodDescriptor, RpcController, Message, RpcCallback)},
60     * if any.
61     */
62    // TODO: it would be good widen this to just Throwable, but IOException is what we allow now
63    private IOException serviceException;
64    private String errorMessage;
65  
66    @Override
67    public void reset() {
68      serviceException = null;
69      errorMessage = null;
70    }
71  
72    @Override
73    public boolean failed() {
74      return (failedOnException() || errorMessage != null);
75    }
76  
77    @Override
78    public String errorText() {
79      return errorMessage;
80    }
81  
82    @Override
83    public void startCancel() {
84      // not implemented
85    }
86  
87    @Override
88    public void setFailed(String message) {
89      errorMessage = message;
90    }
91  
92    @Override
93    public boolean isCanceled() {
94      return false;
95    }
96  
97    @Override
98    public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) {
99      // not implemented
100   }
101 
102   /**
103    * Sets an exception to be communicated back to the {@link Service} client.
104    * @param ioe the exception encountered during execution of the service method
105    */
106   public void setFailedOn(IOException ioe) {
107     serviceException = ioe;
108     setFailed(StringUtils.stringifyException(ioe));
109   }
110 
111   /**
112    * Returns any exception thrown during service method invocation, or {@code null} if no exception
113    * was thrown.  This can be used by clients to receive exceptions generated by RPC calls, even
114    * when {@link RpcCallback}s are used and no {@link com.google.protobuf.ServiceException} is
115    * declared.
116    */
117   public IOException getFailedOn() {
118     return serviceException;
119   }
120 
121   /**
122    * Returns whether or not a server exception was generated in the prior RPC invocation.
123    */
124   public boolean failedOnException() {
125     return serviceException != null;
126   }
127 
128   /**
129    * Throws an IOException back out if one is currently stored.
130    */
131   public void checkFailed() throws IOException {
132     if (failedOnException()) {
133       throw getFailedOn();
134     }
135   }
136 }