spark MessageEncoder 源码

spark MessageEncoder 代码

文件路径：/common/network-common/src/main/java/org/apache/spark/network/protocol/MessageEncoder.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.spark.network.protocol;

import java.util.List;

import io.netty.buffer.ByteBuf;
import io.netty.channel.ChannelHandler;
import io.netty.channel.ChannelHandlerContext;
import io.netty.handler.codec.MessageToMessageEncoder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Encoder used by the server side to encode server-to-client responses.
 * This encoder is stateless so it is safe to be shared by multiple threads.
 */
@ChannelHandler.Sharable
public final class MessageEncoder extends MessageToMessageEncoder<Message> {

  private static final Logger logger = LoggerFactory.getLogger(MessageEncoder.class);

  public static final MessageEncoder INSTANCE = new MessageEncoder();

  private MessageEncoder() {}

  /***
   * Encodes a Message by invoking its encode() method. For non-data messages, we will add one
   * ByteBuf to 'out' containing the total frame length, the message type, and the message itself.
   * In the case of a ChunkFetchSuccess, we will also add the ManagedBuffer corresponding to the
   * data to 'out', in order to enable zero-copy transfer.
   */
  @Override
  public void encode(ChannelHandlerContext ctx, Message in, List<Object> out) throws Exception {
    Object body = null;
    long bodyLength = 0;
    boolean isBodyInFrame = false;

    // If the message has a body, take it out to enable zero-copy transfer for the payload.
    if (in.body() != null) {
      try {
        bodyLength = in.body().size();
        body = in.body().convertToNetty();
        isBodyInFrame = in.isBodyInFrame();
      } catch (Exception e) {
        in.body().release();
        if (in instanceof AbstractResponseMessage) {
          AbstractResponseMessage resp = (AbstractResponseMessage) in;
          // Re-encode this message as a failure response.
          String error = e.getMessage() != null ? e.getMessage() : "null";
          logger.error(String.format("Error processing %s for client %s",
            in, ctx.channel().remoteAddress()), e);
          encode(ctx, resp.createFailureResponse(error), out);
        } else {
          throw e;
        }
        return;
      }
    }

    Message.Type msgType = in.type();
    // All messages have the frame length, message type, and message itself. The frame length
    // may optionally include the length of the body data, depending on what message is being
    // sent.
    int headerLength = 8 + msgType.encodedLength() + in.encodedLength();
    long frameLength = headerLength + (isBodyInFrame ? bodyLength : 0);
    ByteBuf header = ctx.alloc().buffer(headerLength);
    header.writeLong(frameLength);
    msgType.encode(header);
    in.encode(header);
    assert header.writableBytes() == 0;

    if (body != null) {
      // We transfer ownership of the reference on in.body() to MessageWithHeader.
      // This reference will be freed when MessageWithHeader.deallocate() is called.
      out.add(new MessageWithHeader(in.body(), header, body, bodyLength));
    } else {
      out.add(header);
    }
  }

}

相关信息

spark 源码目录

相关文章

spark AbstractMessage 源码

spark AbstractResponseMessage 源码

spark ChunkFetchFailure 源码

spark ChunkFetchRequest 源码

spark ChunkFetchSuccess 源码

spark Encodable 源码

spark Encoders 源码

spark MergedBlockMetaRequest 源码

spark MergedBlockMetaSuccess 源码

spark Message 源码