hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/protocolPB/JournalProtocolServerSideTranslatorPB.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hdfs.protocolPB;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.hdfs.protocol.proto.JournalProtocolProtos.JournalRequestProto;
import org.apache.hadoop.hdfs.protocol.proto.JournalProtocolProtos.JournalResponseProto;
import org.apache.hadoop.hdfs.protocol.proto.JournalProtocolProtos.StartLogSegmentRequestProto;
import org.apache.hadoop.hdfs.protocol.proto.JournalProtocolProtos.StartLogSegmentResponseProto;
import org.apache.hadoop.hdfs.protocolR23Compatible.ProtocolSignatureWritable;
import org.apache.hadoop.hdfs.server.protocol.JournalProtocol;
import org.apache.hadoop.ipc.ProtocolSignature;
import org.apache.hadoop.ipc.RPC;
import org.apache.hadoop.ipc.VersionedProtocol;

import com.google.protobuf.RpcController;
import com.google.protobuf.ServiceException;

/**
 * Implementation for protobuf service that forwards requests
 * received on {@link JournalProtocolPB} to the 
 * {@link JournalProtocol} server implementation.
 */
@InterfaceAudience.Private
public class JournalProtocolServerSideTranslatorPB implements JournalProtocolPB {
  /** Server side implementation to delegate the requests to */
  private final JournalProtocol impl;

  public JournalProtocolServerSideTranslatorPB(JournalProtocol impl) {
    this.impl = impl;
  }

  /** @see JournalProtocol#journal */
  @Override
  public JournalResponseProto journal(RpcController unused,
      JournalRequestProto req) throws ServiceException {
    try {
      impl.journal(PBHelper.convert(req.getRegistration()),
          req.getFirstTxnId(), req.getNumTxns(), req.getRecords()
              .toByteArray());
    } catch (IOException e) {
      throw new ServiceException(e);
    }
    return JournalResponseProto.newBuilder().build();
  }

  /** @see JournalProtocol#startLogSegment */
  @Override
  public StartLogSegmentResponseProto startLogSegment(RpcController controller,
      StartLogSegmentRequestProto req) throws ServiceException {
    try {
      impl.startLogSegment(PBHelper.convert(req.getRegistration()),
          req.getTxid());
    } catch (IOException e) {
      throw new ServiceException(e);
    }
    return StartLogSegmentResponseProto.newBuilder().build();
  }

  /** @see VersionedProtocol#getProtocolVersion */
  @Override
  public long getProtocolVersion(String protocol, long clientVersion)
      throws IOException {
    return RPC.getProtocolVersion(JournalProtocolPB.class);
  }

  /**
   * The client side will redirect getProtocolSignature to
   * getProtocolSignature2.
   * 
   * However the RPC layer below on the Server side will call getProtocolVersion
   * and possibly in the future getProtocolSignature. Hence we still implement
   * it even though the end client will never call this method.
   * 
   * @see VersionedProtocol#getProtocolSignature(String, long, int)
   */
  @Override
  public ProtocolSignature getProtocolSignature(String protocol,
      long clientVersion, int clientMethodsHash) throws IOException {
    /**
     * Don't forward this to the server. The protocol version and signature is
     * that of {@link JournalProtocol}
     */
    if (!protocol.equals(RPC.getProtocolName(JournalProtocolPB.class))) {
      throw new IOException("Namenode Serverside implements " +
          RPC.getProtocolName(JournalProtocolPB.class) +
          ". The following requested protocol is unknown: " + protocol);
    }

    return ProtocolSignature.getProtocolSignature(clientMethodsHash,
        RPC.getProtocolVersion(JournalProtocolPB.class),
        JournalProtocolPB.class);
  }


  @Override
  public ProtocolSignatureWritable getProtocolSignature2(String protocol,
      long clientVersion, int clientMethodsHash) throws IOException {
    /**
     * Don't forward this to the server. The protocol version and signature is
     * that of {@link JournalPBProtocol}
     */
    return ProtocolSignatureWritable.convert(
        this.getProtocolSignature(protocol, clientVersion, clientMethodsHash));
  }
}