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 java.io.IOException;
021import org.apache.hadoop.util.StringUtils;
022import org.apache.yetus.audience.InterfaceAudience;
023
024import org.apache.hbase.thirdparty.com.google.protobuf.RpcCallback;
025import org.apache.hbase.thirdparty.com.google.protobuf.RpcController;
026
027/**
028 * Used for server-side protobuf RPC service invocations. This handler allows invocation exceptions
029 * to easily be passed through to the RPC server from coprocessor
030 * {@link org.apache.hbase.thirdparty.com.google.protobuf.Service} implementations.
031 * <p/>
032 * When implementing {@link org.apache.hbase.thirdparty.com.google.protobuf.Service} defined
033 * methods, coprocessor endpoints can use the following pattern to pass exceptions back to the RPC
034 * client: <code>
035 * public void myMethod(RpcController controller, MyRequest request,
036 *     RpcCallback&lt;MyResponse&gt; done) {
037 *   MyResponse response = null;
038 *   try {
039 *     // do processing
040 *     response = MyResponse.getDefaultInstance();  // or use a new builder to populate the response
041 *   } catch (IOException ioe) {
042 *     // pass exception back up
043 *     ResponseConverter.setControllerException(controller, ioe);
044 *   }
045 *   done.run(response);
046 * }
047 * </code>
048 */
049@InterfaceAudience.Private
050public class ServerRpcController implements RpcController {
051  /**
052   * The exception thrown within
053   * {@link com.google.protobuf.Service#callMethod(com.google.protobuf.Descriptors.MethodDescriptor, RpcController, com.google.protobuf.Message, RpcCallback)}
054   * if any.
055   */
056  // TODO: it would be good widen this to just Throwable, but IOException is what we allow now
057  private IOException serviceException;
058  private String errorMessage;
059
060  @Override
061  public void reset() {
062    serviceException = null;
063    errorMessage = null;
064  }
065
066  @Override
067  public boolean failed() {
068    return (failedOnException() || errorMessage != null);
069  }
070
071  @Override
072  public String errorText() {
073    return errorMessage;
074  }
075
076  @Override
077  public void startCancel() {
078    // not implemented
079  }
080
081  @Override
082  public void setFailed(String message) {
083    errorMessage = message;
084  }
085
086  @Override
087  public boolean isCanceled() {
088    return false;
089  }
090
091  @Override
092  public void notifyOnCancel(RpcCallback<Object> objectRpcCallback) {
093    // not implemented
094  }
095
096  /**
097   * Sets an exception to be communicated back to the
098   * {@link org.apache.hbase.thirdparty.com.google.protobuf.Service} client.
099   * @param ioe the exception encountered during execution of the service method
100   */
101  public void setFailedOn(IOException ioe) {
102    serviceException = ioe;
103    setFailed(StringUtils.stringifyException(ioe));
104  }
105
106  /**
107   * Returns any exception thrown during service method invocation, or {@code null} if no exception
108   * was thrown. This can be used by clients to receive exceptions generated by RPC calls, even when
109   * {@link RpcCallback}s are used and no
110   * {@link org.apache.hbase.thirdparty.com.google.protobuf.ServiceException} is declared.
111   */
112  public IOException getFailedOn() {
113    return serviceException;
114  }
115
116  /**
117   * Returns whether or not a server exception was generated in the prior RPC invocation.
118   */
119  public boolean failedOnException() {
120    return serviceException != null;
121  }
122
123  /**
124   * Throws an IOException back out if one is currently stored.
125   */
126  public void checkFailed() throws IOException {
127    if (failedOnException()) {
128      throw getFailedOn();
129    }
130  }
131}