content: /*
   * 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.io.IOException;
  import java.net.InetSocketAddress;
  import java.net.SocketAddress;
  import java.util.List;
  import java.util.Random;
  import java.util.concurrent.ConcurrentHashMap;
  import java.util.concurrent.atomic.AtomicReference;
  
  import com.google.common.base.Preconditions;
  import com.google.common.base.Throwables;
  import com.google.common.collect.Lists;
  import io.netty.bootstrap.Bootstrap;
  import io.netty.buffer.PooledByteBufAllocator;
  import io.netty.channel.Channel;
  import io.netty.channel.ChannelFuture;
  import io.netty.channel.ChannelInitializer;
  import io.netty.channel.ChannelOption;
  import io.netty.channel.EventLoopGroup;
  import io.netty.channel.socket.SocketChannel;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.spark.network.TransportContext;
  import org.apache.spark.network.server.TransportChannelHandler;
  import org.apache.spark.network.util.IOMode;
  import org.apache.spark.network.util.JavaUtils;
  import org.apache.spark.network.util.NettyUtils;
  import org.apache.spark.network.util.TransportConf;
  
  /**
   * Factory for creating {@link TransportClient}s by using createClient.
   *
   * The factory maintains a connection pool to other hosts and should return the same
   * TransportClient for the same remote host. It also shares a single worker thread pool for
   * all TransportClients.
   *
   * TransportClients will be reused whenever possible. Prior to completing the creation of a new
   * TransportClient, all given {@link TransportClientBootstrap}s will be run.
   */
  public class TransportClientFactory implements Closeable {
  
    /** A simple data structure to track the pool of clients between two peer nodes. */
    private static class ClientPool {
      TransportClient[] clients;
      Object[] locks;
  
      ClientPool(int size) {
        clients = new TransportClient[size];
        locks = new Object[size];
        for (int i = 0; i < size; i++) {
          locks[i] = new Object();
        }
      }
    }
  
    private static final Logger logger = LoggerFactory.getLogger(TransportClientFactory.class);
  
    private final TransportContext context;
    private final TransportConf conf;
    private final List<TransportClientBootstrap> clientBootstraps;
    private final ConcurrentHashMap<SocketAddress, ClientPool> connectionPool;
  
    /** Random number generator for picking connections between peers. */
    private final Random rand;
    private final int numConnectionsPerPeer;
  
    private final Class<? extends Channel> socketChannelClass;
    private EventLoopGroup workerGroup;
    private PooledByteBufAllocator pooledAllocator;
  
    public TransportClientFactory(
        TransportContext context,
        List<TransportClientBootstrap> clientBootstraps) {
      this.context = Preconditions.checkNotNull(context);
      this.conf = context.getConf();
      this.clientBootstraps = Lists.newArrayList(Preconditions.checkNotNull(clientBootstraps));
      this.connectionPool = new ConcurrentHashMap<>();
      this.numConnectionsPerPeer = conf.numConnectionsPerPeer();
      this.rand = new Random();
  
      IOMode ioMode = IOMode.valueOf(conf.ioMode());
      this.socketChannelClass = NettyUtils.getClientChannelClass(ioMode);
      // TODO: Make thread pool name configurable.
      this.workerGroup = NettyUtils.createEventLoop(ioMode, conf.clientThreads(), "shuffle-client");
      this.pooledAllocator = NettyUtils.createPooledByteBufAllocator(
        conf.preferDirectBufs(), false /* allowCache */, conf.clientThreads());
    }
  
    /**
     * Create a {@link TransportClient} connecting to the given remote host / port.
     *
     * We maintains an array of clients (size determined by spark.shuffle.io.numConnectionsPerPeer)
     * and randomly picks one to use. If no client was previously created in the randomly selected
     * spot, this function creates a new client and places it there.
     *
     * Prior to the creation of a new TransportClient, we will execute all
     * {@link TransportClientBootstrap}s that are registered with this factory.
     *
     * This blocks until a connection is successfully established and fully bootstrapped.
     *
     * Concurrency: This method is safe to call from multiple threads.
     */
    public TransportClient createClient(String remoteHost, int remotePort) throws IOException {
      // Get connection from the connection pool first.
      // If it is not found or not active, create a new one.
      // Use unresolved address here to avoid DNS resolution each time we creates a client.
      final InetSocketAddress unresolvedAddress =
        InetSocketAddress.createUnresolved(remoteHost, remotePort);
  
      // Create the ClientPool if we don't have it yet.
      ClientPool clientPool = connectionPool.get(unresolvedAddress);
      if (clientPool == null) {
        connectionPool.putIfAbsent(unresolvedAddress, new ClientPool(numConnectionsPerPeer));
        clientPool = connectionPool.get(unresolvedAddress);
      }
  
      int clientIndex = rand.nextInt(numConnectionsPerPeer);
      TransportClient cachedClient = clientPool.clients[clientIndex];
  
      if (cachedClient != null && cachedClient.isActive()) {
        // Make sure that the channel will not timeout by updating the last use time of the
        // handler. Then check that the client is still alive, in case it timed out before
        // this code was able to update things.
        TransportChannelHandler handler = cachedClient.getChannel().pipeline()
          .get(TransportChannelHandler.class);
        synchronized (handler) {
          handler.getResponseHandler().updateTimeOfLastRequest();
        }
  
        if (cachedClient.isActive()) {
          logger.trace("Returning cached connection to {}: {}",
            cachedClient.getSocketAddress(), cachedClient);
          return cachedClient;
        }
      }
  
      // If we reach here, we don't have an existing connection open. Let's create a new one.
      // Multiple threads might race here to create new connections. Keep only one of them active.
      final long preResolveHost = System.nanoTime();
      final InetSocketAddress resolvedAddress = new InetSocketAddress(remoteHost, remotePort);
      final long hostResolveTimeMs = (System.nanoTime() - preResolveHost) / 1000000;
      if (hostResolveTimeMs > 2000) {
        logger.warn("DNS resolution for {} took {} ms", resolvedAddress, hostResolveTimeMs);
      } else {
        logger.trace("DNS resolution for {} took {} ms", resolvedAddress, hostResolveTimeMs);
      }
  
      synchronized (clientPool.locks[clientIndex]) {
        cachedClient = clientPool.clients[clientIndex];
  
        if (cachedClient != null) {
          if (cachedClient.isActive()) {
            logger.trace("Returning cached connection to {}: {}", resolvedAddress, cachedClient);
            return cachedClient;
          } else {
            logger.info("Found inactive connection to {}, creating a new one.", resolvedAddress);
          }
        }
        clientPool.clients[clientIndex] = createClient(resolvedAddress);
        return clientPool.clients[clientIndex];
      }
    }
  
    /**
     * Create a completely new {@link TransportClient} to the given remote host / port.
     * This connection is not pooled.
     *
     * As with {@link #createClient(String, int)}, this method is blocking.
     */
    public TransportClient createUnmanagedClient(String remoteHost, int remotePort)
        throws IOException {
      final InetSocketAddress address = new InetSocketAddress(remoteHost, remotePort);
      return createClient(address);
    }
  
    /** Create a completely new {@link TransportClient} to the remote address. */
    private TransportClient createClient(InetSocketAddress address) throws IOException {
      logger.debug("Creating new connection to {}", address);
  
      Bootstrap bootstrap = new Bootstrap();
      bootstrap.group(workerGroup)
        .channel(socketChannelClass)
        // Disable Nagle's Algorithm since we don't want packets to wait
        .option(ChannelOption.TCP_NODELAY, true)
        .option(ChannelOption.SO_KEEPALIVE, true)
        .option(ChannelOption.CONNECT_TIMEOUT_MILLIS, conf.connectionTimeoutMs())
        .option(ChannelOption.ALLOCATOR, pooledAllocator);
  
      final AtomicReference<TransportClient> clientRef = new AtomicReference<>();
      final AtomicReference<Channel> channelRef = new AtomicReference<>();
  
      bootstrap.handler(new ChannelInitializer<SocketChannel>() {
        @Override
        public void initChannel(SocketChannel ch) {
          TransportChannelHandler clientHandler = context.initializePipeline(ch);
          clientRef.set(clientHandler.getClient());
          channelRef.set(ch);
        }
      });
  
      // Connect to the remote server
      long preConnect = System.nanoTime();
      ChannelFuture cf = bootstrap.connect(address);
      if (!cf.awaitUninterruptibly(conf.connectionTimeoutMs())) {
        throw new IOException(
          String.format("Connecting to %s timed out (%s ms)", address, conf.connectionTimeoutMs()));
      } else if (cf.cause() != null) {
        throw new IOException(String.format("Failed to connect to %s", address), cf.cause());
      }
  
      TransportClient client = clientRef.get();
      Channel channel = channelRef.get();
      assert client != null : "Channel future completed successfully with null client";
  
      // Execute any client bootstraps synchronously before marking the Client as successful.
      long preBootstrap = System.nanoTime();
      logger.debug("Connection to {} successful, running bootstraps...", address);
      try {
        for (TransportClientBootstrap clientBootstrap : clientBootstraps) {
          clientBootstrap.doBootstrap(client, channel);
        }
      } catch (Exception e) { // catch non-RuntimeExceptions too as bootstrap may be written in Scala
        long bootstrapTimeMs = (System.nanoTime() - preBootstrap) / 1000000;
        logger.error("Exception while bootstrapping client after " + bootstrapTimeMs + " ms", e);
        client.close();
        throw Throwables.propagate(e);
      }
      long postBootstrap = System.nanoTime();
  
      logger.info("Successfully created connection to {} after {} ms ({} ms spent in bootstraps)",
        address, (postBootstrap - preConnect) / 1000000, (postBootstrap - preBootstrap) / 1000000);
  
      return client;
    }
  
    /** Close all connections in the connection pool, and shutdown the worker thread pool. */
    @Override
    public void close() {
      // Go through all clients and close them if they are active.
      for (ClientPool clientPool : connectionPool.values()) {
        for (int i = 0; i < clientPool.clients.length; i++) {
          TransportClient client = clientPool.clients[i];
          if (client != null) {
            clientPool.clients[i] = null;
            JavaUtils.closeQuietly(client);
          }
        }
      }
      connectionPool.clear();
  
      if (workerGroup != null) {
        workerGroup.shutdownGracefully();
        workerGroup = null;
      }
    }
  }
  