Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/2753#discussion_r18810179
--- Diff:
network/common/src/main/java/org/apache/spark/network/client/SluiceClient.java
---
@@ -0,0 +1,161 @@
+/*
+ * 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 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;
+
+/**
+ * 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 Sluice.
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 SluiceClient using {@link
SluiceClientFactory}. A single SluiceClient
+ * 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
SluiceClientHandler} is
+ * responsible for handling responses from the server.
+ *
+ * Concurrency: thread safe and can be called from multiple threads.
+ */
+public class SluiceClient implements Closeable {
+ private final Logger logger =
LoggerFactory.getLogger(SluiceClient.class);
+
+ private final ChannelFuture cf;
+ private final SluiceClientHandler handler;
+
+ private final String serverAddr;
+
+ SluiceClient(ChannelFuture cf, SluiceClientHandler handler) {
+ this.cf = cf;
+ this.handler = handler;
+
+ if (cf != null && cf.channel() != null && cf.channel().remoteAddress()
!= null) {
+ serverAddr = cf.channel().remoteAddress().toString();
+ } else {
+ serverAddr = "<unknown address>";
+ }
+ }
+
+ public boolean isActive() {
+ return cf.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 SluiceClient
+ * 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 long startTime = System.currentTimeMillis();
+ logger.debug("Sending fetch chunk request {} to {}", chunkIndex,
serverAddr);
+
+ final StreamChunkId streamChunkId = new StreamChunkId(streamId,
chunkIndex);
+ handler.addFetchRequest(streamChunkId, callback);
+
+ cf.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,
+ timeTaken);
+ } else {
+ // Fail all blocks.
+ String errorMsg = String.format("Failed to send request %s to
%s: %s", streamChunkId,
+ serverAddr, future.cause().getMessage());
+ logger.error(errorMsg, future.cause());
+ future.cause().printStackTrace();
+ handler.removeFetchRequest(streamChunkId);
+ callback.onFailure(chunkIndex, new RuntimeException(errorMsg));
+ }
+ }
+ });
+ }
+
+ /**
+ * Sends an opaque message to the RpcHandler on the server-side. The
callback will be invoked
+ * with the server's response or upon any failure.
+ */
+ public void sendRpc(byte[] message, final RpcResponseCallback callback) {
--- End diff --
rather than byte[], how about just an Object, and the server/client takes a
configurable serializer that does the serialization?
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