Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/1907#discussion_r16212159
--- Diff:
core/src/main/scala/org/apache/spark/network/netty/client/BlockFetchingClientHandler.scala
---
@@ -0,0 +1,63 @@
+/*
+ * 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.client
+
+import io.netty.buffer.ByteBuf
+import io.netty.channel.{ChannelHandlerContext,
SimpleChannelInboundHandler}
+
+import org.apache.spark.Logging
+
+
+/**
+ * Handler that processes server responses. It uses the protocol
documented in
+ * [[org.apache.spark.network.netty.server.BlockServer]].
+ */
+private[client]
+class BlockFetchingClientHandler extends
SimpleChannelInboundHandler[ByteBuf] with Logging {
+
+ var blockFetchSuccessCallback: (String, ReferenceCountedBuffer) => Unit
= _
+ var blockFetchFailureCallback: (String, String) => Unit = _
+
+ override def exceptionCaught(ctx: ChannelHandlerContext, cause:
Throwable): Unit = {
+ logError(s"Exception in connection from ${ctx.channel.remoteAddress}",
cause)
+ ctx.close()
+ }
+
+ override def channelRead0(ctx: ChannelHandlerContext, in: ByteBuf) {
+ val totalLen = in.readInt()
--- End diff --
On the write side we need to write 2 messages to take care of zero-copy
send (one for header and one for DefaultFileRegion that uses transferTo under
the hood). On the receive side they get combined into a single message by a
LengthFieldBasedFrameDecoder so we don't need extra complexity to handle
correlating the two messages. That makes it harder to accomplish what you are
suggesting (not impossible but harder -- I'd have to ).
The unit test coverage for this is actually pretty comprehensive. If the
wire protocol becomes more complicated, we should definitely revisit this.
That said, I have some ideas that can make this more obvious. I wouldn't
let those block this pull request though.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at [email protected] or file a JIRA ticket
with INFRA.
---
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
