Java tutorial
/* * 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.server; import java.util.Iterator; import java.util.Map; import java.util.Random; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.atomic.AtomicLong; import com.google.common.base.Preconditions; import io.netty.channel.Channel; import org.apache.commons.lang3.tuple.ImmutablePair; import org.apache.commons.lang3.tuple.Pair; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.apache.spark.network.buffer.ManagedBuffer; import org.apache.spark.network.client.TransportClient; /** * StreamManager which allows registration of an Iterator<ManagedBuffer>, which are * individually fetched as chunks by the client. Each registered buffer is one chunk. */ public class OneForOneStreamManager extends StreamManager { private static final Logger logger = LoggerFactory.getLogger(OneForOneStreamManager.class); private final AtomicLong nextStreamId; private final ConcurrentHashMap<Long, StreamState> streams; /** State of a single stream. */ private static class StreamState { final String appId; final Iterator<ManagedBuffer> buffers; // The channel associated to the stream Channel associatedChannel = null; // Used to keep track of the index of the buffer that the user has retrieved, just to ensure // that the caller only requests each chunk one at a time, in order. int curChunk = 0; // Used to keep track of the number of chunks being transferred and not finished yet. volatile long chunksBeingTransferred = 0L; StreamState(String appId, Iterator<ManagedBuffer> buffers) { this.appId = appId; this.buffers = Preconditions.checkNotNull(buffers); } } public OneForOneStreamManager() { // For debugging purposes, start with a random stream id to help identifying different streams. // This does not need to be globally unique, only unique to this class. nextStreamId = new AtomicLong((long) new Random().nextInt(Integer.MAX_VALUE) * 1000); streams = new ConcurrentHashMap<>(); } @Override public void registerChannel(Channel channel, long streamId) { if (streams.containsKey(streamId)) { streams.get(streamId).associatedChannel = channel; } } @Override public ManagedBuffer getChunk(long streamId, int chunkIndex) { StreamState state = streams.get(streamId); if (chunkIndex != state.curChunk) { throw new IllegalStateException(String.format("Received out-of-order chunk index %s (expected %s)", chunkIndex, state.curChunk)); } else if (!state.buffers.hasNext()) { throw new IllegalStateException(String.format("Requested chunk index beyond end %s", chunkIndex)); } state.curChunk += 1; ManagedBuffer nextChunk = state.buffers.next(); if (!state.buffers.hasNext()) { logger.trace("Removing stream id {}", streamId); streams.remove(streamId); } return nextChunk; } @Override public ManagedBuffer openStream(String streamChunkId) { Pair<Long, Integer> streamChunkIdPair = parseStreamChunkId(streamChunkId); return getChunk(streamChunkIdPair.getLeft(), streamChunkIdPair.getRight()); } public static String genStreamChunkId(long streamId, int chunkId) { return String.format("%d_%d", streamId, chunkId); } // Parse streamChunkId to be stream id and chunk id. This is used when fetch remote chunk as a // stream. public static Pair<Long, Integer> parseStreamChunkId(String streamChunkId) { String[] array = streamChunkId.split("_"); assert array.length == 2 : "Stream id and chunk index should be specified."; long streamId = Long.valueOf(array[0]); int chunkIndex = Integer.valueOf(array[1]); return ImmutablePair.of(streamId, chunkIndex); } @Override public void connectionTerminated(Channel channel) { // Close all streams which have been associated with the channel. for (Map.Entry<Long, StreamState> entry : streams.entrySet()) { StreamState state = entry.getValue(); if (state.associatedChannel == channel) { streams.remove(entry.getKey()); // Release all remaining buffers. while (state.buffers.hasNext()) { state.buffers.next().release(); } } } } @Override public void checkAuthorization(TransportClient client, long streamId) { if (client.getClientId() != null) { StreamState state = streams.get(streamId); Preconditions.checkArgument(state != null, "Unknown stream ID."); if (!client.getClientId().equals(state.appId)) { throw new SecurityException(String.format("Client %s not authorized to read stream %d (app %s).", client.getClientId(), streamId, state.appId)); } } } @Override public void chunkBeingSent(long streamId) { StreamState streamState = streams.get(streamId); if (streamState != null) { streamState.chunksBeingTransferred++; } } @Override public void streamBeingSent(String streamId) { chunkBeingSent(parseStreamChunkId(streamId).getLeft()); } @Override public void chunkSent(long streamId) { StreamState streamState = streams.get(streamId); if (streamState != null) { streamState.chunksBeingTransferred--; } } @Override public void streamSent(String streamId) { chunkSent(OneForOneStreamManager.parseStreamChunkId(streamId).getLeft()); } @Override public long chunksBeingTransferred() { long sum = 0L; for (StreamState streamState : streams.values()) { sum += streamState.chunksBeingTransferred; } return sum; } /** * Registers a stream of ManagedBuffers which are served as individual chunks one at a time to * callers. Each ManagedBuffer will be release()'d after it is transferred on the wire. If a * client connection is closed before the iterator is fully drained, then the remaining buffers * will all be release()'d. * * If an app ID is provided, only callers who've authenticated with the given app ID will be * allowed to fetch from this stream. */ public long registerStream(String appId, Iterator<ManagedBuffer> buffers) { long myStreamId = nextStreamId.getAndIncrement(); streams.put(myStreamId, new StreamState(appId, buffers)); return myStreamId; } }