Github user aarondav commented on a diff in the pull request:
https://github.com/apache/spark/pull/2330#discussion_r17463888
--- Diff: core/src/main/scala/org/apache/spark/network/netty/protocol.scala
---
@@ -0,0 +1,260 @@
+/*
+ * 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.netty
+
+import java.util.{List => JList}
+
+import io.netty.buffer.ByteBuf
+import io.netty.channel.ChannelHandlerContext
+import io.netty.channel.ChannelHandler.Sharable
+import io.netty.handler.codec._
+
+import org.apache.spark.Logging
+import org.apache.spark.network.{NettyManagedBuffer, ManagedBuffer}
+
+
+/** Messages from the client to the server. */
+sealed trait ClientRequest {
+ def id: Byte
+}
+
+/**
+ * Request to fetch a sequence of blocks from the server. A single
[[BlockFetchRequest]] can
+ * correspond to multiple [[ServerResponse]]s.
+ */
+final case class BlockFetchRequest(blocks: Seq[String]) extends
ClientRequest {
+ override def id = 0
+}
+
+/**
+ * Request to upload a block to the server. Currently the server does not
ack the upload request.
+ */
+final case class BlockUploadRequest(blockId: String, data: ManagedBuffer)
extends ClientRequest {
+ require(blockId.length <= Byte.MaxValue)
+ override def id = 1
+}
+
+
+/** Messages from server to client (usually in response to some
[[ClientRequest]]. */
+sealed trait ServerResponse {
+ def id: Byte
+}
+
+/** Response to [[BlockFetchRequest]] when a block exists and has been
successfully fetched. */
+final case class BlockFetchSuccess(blockId: String, data: ManagedBuffer)
extends ServerResponse {
+ require(blockId.length <= Byte.MaxValue)
+ override def id = 0
+}
+
+/** Response to [[BlockFetchRequest]] when there is an error fetching the
block. */
+final case class BlockFetchFailure(blockId: String, error: String) extends
ServerResponse {
+ require(blockId.length <= Byte.MaxValue)
+ override def id = 1
+}
+
+
+/**
+ * Encoder for [[ClientRequest]] used in client side.
+ *
+ * This encoder is stateless so it is safe to be shared by multiple
threads.
+ */
+@Sharable
+final class ClientRequestEncoder extends
MessageToMessageEncoder[ClientRequest] {
+ override def encode(ctx: ChannelHandlerContext, in: ClientRequest, out:
JList[Object]): Unit = {
+ in match {
+ case BlockFetchRequest(blocks) =>
+ // 8 bytes: frame size
+ // 1 byte: BlockFetchRequest vs BlockUploadRequest
+ // 4 byte: num blocks
+ // then for each block id write 1 byte for blockId.length and then
blockId itself
+ val frameLength = 8 + 1 + 4 + blocks.size +
blocks.map(_.size).fold(0)(_ + _)
+ val buf = ctx.alloc().buffer(frameLength)
+
+ buf.writeLong(frameLength)
+ buf.writeByte(in.id)
+ buf.writeInt(blocks.size)
+ blocks.foreach { blockId =>
+ ProtocolUtils.writeBlockId(buf, blockId)
+ }
+
+ assert(buf.writableBytes() == 0)
+ out.add(buf)
+
+ case BlockUploadRequest(blockId, data) =>
+ // 8 bytes: frame size
+ // 1 byte: msg id (BlockFetchRequest vs BlockUploadRequest)
+ // 1 byte: blockId.length
+ // data itself (length can be derived from: frame size - 1 -
blockId.length)
+ val headerLength = 8 + 1 + 1 + blockId.length
+ val frameLength = headerLength + data.size
+ val header = ctx.alloc().buffer(headerLength)
+
+ // Call this before we add header to out so in case of exceptions
+ // we don't send anything at all.
+ val body = data.convertToNetty()
+
+ header.writeLong(frameLength)
+ header.writeByte(in.id)
+ ProtocolUtils.writeBlockId(header, blockId)
+
+ assert(header.writableBytes() == 0)
+ out.add(header)
+ out.add(body)
+ }
+ }
+}
+
+
+/**
+ * Decoder in the server side to decode client requests.
+ * This decoder is stateless so it is safe to be shared by multiple
threads.
+ *
+ * This assumes the inbound messages have been processed by a frame
decoder created by
+ * [[ProtocolUtils.createFrameDecoder()]].
+ */
+@Sharable
+final class ClientRequestDecoder extends MessageToMessageDecoder[ByteBuf] {
+ override protected def decode(ctx: ChannelHandlerContext, in: ByteBuf,
out: JList[AnyRef]): Unit =
+ {
+ val msgTypeId = in.readByte()
+ val decoded = msgTypeId match {
+ case 0 => // BlockFetchRequest
+ val numBlocks = in.readInt()
+ val blockIds = Seq.fill(numBlocks) { ProtocolUtils.readBlockId(in)
}
+ BlockFetchRequest(blockIds)
+
+ case 1 => // BlockUploadRequest
+ val blockId = ProtocolUtils.readBlockId(in)
+ in.retain() // retain the bytebuf so we don't recycle it
immediately.
+ BlockUploadRequest(blockId, new NettyManagedBuffer(in))
+ }
+
+ assert(decoded.id == msgTypeId)
+ out.add(decoded)
+ }
+}
+
+
+/**
+ * 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.
+ */
+@Sharable
+final class ServerResponseEncoder extends
MessageToMessageEncoder[ServerResponse] with Logging {
+ override def encode(ctx: ChannelHandlerContext, in: ServerResponse, out:
JList[Object]): Unit = {
+ in match {
+ case BlockFetchSuccess(blockId, data) =>
+ // Handle the body first so if we encounter an error getting the
body, we can respond
+ // with an error instead.
+ var body: AnyRef = null
+ try {
+ body = data.convertToNetty()
+ } catch {
+ case e: Exception =>
+ // Re-encode this message as BlockFetchFailure.
+ logError(s"Error opening block $blockId for client
${ctx.channel.remoteAddress}", e)
+ encode(ctx, new BlockFetchFailure(blockId, e.getMessage), out)
+ return
+ }
+
+ // If we got here, body cannot be null
+ // 8 bytes = long for frame length
+ // 1 byte = message id (type)
+ // 1 byte = block id length
+ // followed by block id itself
+ val headerLength = 8 + 1 + 1 + blockId.length
+ val frameLength = headerLength + data.size
+ val header = ctx.alloc().buffer(headerLength)
+ header.writeLong(frameLength)
+ header.writeByte(in.id)
+ ProtocolUtils.writeBlockId(header, blockId)
+
+ assert(header.writableBytes() == 0)
+ out.add(header)
+ out.add(body)
+
+ case BlockFetchFailure(blockId, error) =>
+ val frameLength = 8 + 1 + 1 + blockId.length + error.length
+ val buf = ctx.alloc().buffer(frameLength)
+ buf.writeLong(frameLength)
+ buf.writeByte(in.id)
+ ProtocolUtils.writeBlockId(buf, blockId)
+ buf.writeBytes(error.getBytes)
+
+ assert(buf.writableBytes() == 0)
+ out.add(buf)
+ }
+ }
+}
+
+
+/**
+ * Decoder in the client side to decode server responses.
+ * This decoder is stateless so it is safe to be shared by multiple
threads.
+ *
+ * This assumes the inbound messages have been processed by a frame
decoder created by
+ * [[ProtocolUtils.createFrameDecoder()]].
+ */
+@Sharable
+final class ServerResponseDecoder extends MessageToMessageDecoder[ByteBuf]
{
+ override def decode(ctx: ChannelHandlerContext, in: ByteBuf, out:
JList[AnyRef]): Unit = {
+ val msgId = in.readByte()
+ val decoded = msgId match {
+ case 0 => // BlockFetchSuccess
+ val blockId = ProtocolUtils.readBlockId(in)
+ in.retain()
+ new BlockFetchSuccess(blockId, new NettyManagedBuffer(in))
+
+ case 1 => // BlockFetchFailure
+ val blockId = ProtocolUtils.readBlockId(in)
+ val errorBytes = new Array[Byte](in.readableBytes())
+ in.readBytes(errorBytes)
+ new BlockFetchFailure(blockId, new String(errorBytes))
+ }
+
+ assert(decoded.id == msgId)
+ out.add(decoded)
+ }
+}
+
+
+private[netty] object ProtocolUtils {
+
+ /** LengthFieldBasedFrameDecoder used before all decoders. */
+ def createFrameDecoder(): ByteToMessageDecoder = {
+ // maxFrameLength = 2G
+ // lengthFieldOffset = 0
+ // lengthFieldLength = 8
+ // lengthAdjustment = -8, i.e. exclude the 8 byte length itself
+ // initialBytesToStrip = 8, i.e. strip out the length field itself
+ new LengthFieldBasedFrameDecoder(Int.MaxValue, 0, 8, -8, 8)
+ }
+
+ // TODO(rxin): Make sure these work for all charsets.
+ def readBlockId(in: ByteBuf): String = {
+ val numBytesToRead = in.readByte().toInt
--- End diff --
Maybe add a comment that this is guaranteed <128.
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