Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/2753#discussion_r19438953
--- Diff:
network/common/src/main/java/org/apache/spark/network/client/TransportClient.java
---
@@ -0,0 +1,157 @@
+/*
+ * 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.client;
+
+import java.io.Closeable;
+import java.util.UUID;
+import java.util.concurrent.TimeUnit;
+
+import com.google.common.base.Preconditions;
+import io.netty.channel.Channel;
+import io.netty.channel.ChannelFuture;
+import io.netty.channel.ChannelFutureListener;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.apache.spark.network.protocol.StreamChunkId;
+import org.apache.spark.network.protocol.request.ChunkFetchRequest;
+import org.apache.spark.network.protocol.request.RpcRequest;
+import org.apache.spark.network.util.NettyUtils;
+
+/**
+ * Client for fetching consecutive chunks of a pre-negotiated stream. This
API is intended to allow
+ * efficient transfer of a large amount of data, broken up into chunks
with size ranging from
+ * hundreds of KB to a few MB.
+ *
+ * Note that while this client deals with the fetching of chunks from a
stream (i.e., data plane),
+ * the actual setup of the streams is done outside the scope of the
transport layer. The convenience
+ * method "sendRPC" is provided to enable control plane communication
between the client and server
+ * to perform this setup.
+ *
+ * For example, a typical workflow might be:
+ * client.sendRPC(new OpenFile("/foo")) --> returns StreamId = 100
+ * client.fetchChunk(streamId = 100, chunkIndex = 0, callback)
+ * client.fetchChunk(streamId = 100, chunkIndex = 1, callback)
+ * ...
+ * client.sendRPC(new CloseStream(100))
+ *
+ * Construct an instance of TransportClient using {@link
TransportClientFactory}. A single
+ * TransportClient may be used for multiple streams, but any given stream
must be restricted to a
+ * single client, in order to avoid out-of-order responses.
+ *
+ * NB: This class is used to make requests to the server, while {@link
TransportResponseHandler} is
+ * responsible for handling responses from the server.
+ *
+ * Concurrency: thread safe and can be called from multiple threads.
+ */
+public class TransportClient implements Closeable {
+ private final Logger logger =
LoggerFactory.getLogger(TransportClient.class);
+
+ private final Channel channel;
+ private final TransportResponseHandler handler;
+
+ public TransportClient(Channel channel, TransportResponseHandler
handler) {
+ this.channel = Preconditions.checkNotNull(channel);
+ this.handler = Preconditions.checkNotNull(handler);
+ }
+
+ public boolean isActive() {
+ return channel.isOpen() || channel.isActive();
+ }
+
+ /**
+ * Requests a single chunk from the remote side, from the pre-negotiated
streamId.
+ *
+ * Chunk indices go from 0 onwards. It is valid to request the same
chunk multiple times, though
+ * some streams may not support this.
+ *
+ * Multiple fetchChunk requests may be outstanding simultaneously, and
the chunks are guaranteed
+ * to be returned in the same order that they were requested, assuming
only a single
+ * TransportClient is used to fetch the chunks.
+ *
+ * @param streamId Identifier that refers to a stream in the remote
StreamManager. This should
+ * be agreed upon by client and server beforehand.
+ * @param chunkIndex 0-based index of the chunk to fetch
+ * @param callback Callback invoked upon successful receipt of chunk, or
upon any failure.
+ */
+ public void fetchChunk(
+ long streamId,
+ final int chunkIndex,
+ final ChunkReceivedCallback callback) {
+ final String serverAddr = NettyUtils.getRemoteAddress(channel);
+ final long startTime = System.currentTimeMillis();
+ logger.debug("Sending fetch chunk request {} to {}", chunkIndex,
serverAddr);
+
+ final StreamChunkId streamChunkId = new StreamChunkId(streamId,
chunkIndex);
+ handler.addFetchRequest(streamChunkId, callback);
+
+ channel.writeAndFlush(new
ChunkFetchRequest(streamChunkId)).addListener(
+ new ChannelFutureListener() {
+ @Override
+ public void operationComplete(ChannelFuture future) throws
Exception {
+ if (future.isSuccess()) {
+ long timeTaken = System.currentTimeMillis() - startTime;
+ logger.debug("Sending request {} to {} took {} ms",
streamChunkId, serverAddr,
--- End diff --
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