PollingServer.java

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/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


import java.io.*;
import java.net.*;
import java.lang.Byte;

/**
 * Simple Java "server" using the Poller class
 * to multiplex on incoming connections.  Note
 * that handoff of events, via linked Q is not
 * actually be a performance booster here, since
 * the processing of events is cheaper than
 * the overhead in scheduling/executing them.
 * Although this demo does allow for concurrency
 * in handling connections, it uses a rather
 * primitive "gang scheduling" policy to keep
 * the code simpler.
 */

public class PollingServer
{
  public final static int MAXCONN    = 10000;
  public final static int PORTNUM    = 4444;
  public final static int BYTESPEROP = 10;

  /**
   * This synchronization object protects access to certain
   * data (bytesRead,eventsToProcess) by concurrent Consumer threads.
   */
  private final static Object eventSync = new Object();

  private static InputStream[] instr = new InputStream[MAXCONN];
  private static int[] mapping = new int[65535];
  private static LinkedQueue linkedQ = new LinkedQueue();
  private static int bytesRead = 0;
  private static int bytesToRead;
  private static int eventsToProcess=0;

  public PollingServer(int concurrency) {
    Socket[] sockArr = new Socket[MAXCONN];
    long timestart, timestop;
    short[] revents = new short[MAXCONN];
    int[] fds = new int[MAXCONN];
    int bytes;
    Poller Mux;
    int serverFd;
    int totalConn=0;
    int connects=0;

    System.out.println ("Serv: Initializing port " + PORTNUM);
    try {

      ServerSocket skMain = new ServerSocket (PORTNUM);
      /*
       * Create the Poller object Mux, allow for up to MAXCONN
       * sockets/filedescriptors to be polled.
       */
      Mux = new Poller(MAXCONN);
      serverFd = Mux.add(skMain, Poller.POLLIN);

      Socket ctrlSock = skMain.accept();

      BufferedReader ctrlReader =
        new BufferedReader(new InputStreamReader(ctrlSock.getInputStream()));
      String ctrlString = ctrlReader.readLine();
      bytesToRead = Integer.valueOf(ctrlString).intValue();
      ctrlString = ctrlReader.readLine();
      totalConn = Integer.valueOf(ctrlString).intValue();

      System.out.println("Receiving " + bytesToRead + " bytes from " +
                         totalConn + " client connections");

      timestart = System.currentTimeMillis();

      /*
       * Start the consumer threads to read data.
       */
      for (int consumerThread = 0;
           consumerThread < concurrency; consumerThread++ ) {
        new Consumer(consumerThread).start();
      }

      /*
       * Take connections, read Data
       */
      int numEvents=0;

      while ( bytesRead < bytesToRead ) {

        int loopWaits=0;
        while (eventsToProcess > 0) {
          synchronized (eventSync) {
            loopWaits++;
            if (eventsToProcess <= 0) break;
            try { eventSync.wait(); } catch (Exception e) {e.printStackTrace();};
          }
        }
        if (loopWaits > 1)
          System.out.println("Done waiting...loops = " + loopWaits +
                             " events " + numEvents +
                             " bytes read : " + bytesRead );

        if (bytesRead >= bytesToRead) break; // may be done!

        /*
         * Wait for events
         */
        numEvents = Mux.waitMultiple(100, fds, revents);
        synchronized (eventSync) {
          eventsToProcess = numEvents;
        }
        /*
         * Process all the events we got from Mux.waitMultiple
         */
        int cnt = 0;
        while ( (cnt < numEvents) && (bytesRead < bytesToRead) ) {
          int fd = fds[cnt];

          if (revents[cnt] == Poller.POLLIN) {
            if (fd == serverFd) {
              /*
               * New connection coming in on the ServerSocket
               * Add the socket to the Mux, keep track of mapping
               * the fdval returned by Mux.add to the connection.
               */
              sockArr[connects] = skMain.accept();
              instr[connects] = sockArr[connects].getInputStream();
              int fdval = Mux.add(sockArr[connects], Poller.POLLIN);
              mapping[fdval] = connects;
              synchronized(eventSync) {
                eventsToProcess--; // just processed this one!
              }
              connects++;
            } else {
              /*
               * We've got data from this client connection.
               * Put it on the queue for the consumer threads to process.
               */
              linkedQ.put(new Integer(fd));
            }
          } else {
            System.out.println("Got revents[" + cnt + "] == " + revents[cnt]);
          }
          cnt++;
        }
      }
      timestop = System.currentTimeMillis();
      System.out.println("Time for all reads (" + totalConn +
                         " sockets) : " + (timestop-timestart));

      // Tell the client it can now go away
      byte[] buff = new byte[BYTESPEROP];
      ctrlSock.getOutputStream().write(buff,0,BYTESPEROP);

      // Tell the cunsumer threads they can exit.
      for (int cThread = 0; cThread < concurrency; cThread++ ) {
        linkedQ.put(new Integer(-1));
      }
    } catch (Exception exc) { exc.printStackTrace(); }
  }

  /*
   * main ... just check if a concurrency was specified
   */
  public static void main (String args[])
  {
    int concurrency;

    if (args.length == 1)
      concurrency = java.lang.Integer.valueOf(args[0]).intValue();
    else
      concurrency = Poller.getNumCPUs() + 1;
    PollingServer server = new PollingServer(concurrency);
  }

  /*
   * This class is for handling the Client data.
   * The PollingServer spawns off a number of these based upon
   * the number of CPUs (or concurrency argument).
   * Each just loops grabbing events off the queue and
   * processing them.
   */
  class Consumer extends Thread {
    private int threadNumber;
    public Consumer(int i) { threadNumber = i; }

    public void run() {
      byte[] buff = new byte[BYTESPEROP];
      int bytes = 0;

      InputStream instream;
      while (bytesRead < bytesToRead) {
        try {
          Integer Fd = (Integer) linkedQ.take();
          int fd = Fd.intValue();
          if (fd == -1) break; /* got told we could exit */

          /*
           * We have to map the fd value returned from waitMultiple
           * to the actual input stream associated with that fd.
           * Take a look at how the Mux.add() was done to see how
           * we stored that.
           */
          int map = mapping[fd];
          instream = instr[map];
          bytes = instream.read(buff,0,BYTESPEROP);
        } catch (Exception e) { System.out.println(e.toString()); }

        if (bytes > 0) {
          /*
           * Any real server would do some synchronized and some
           * unsynchronized work on behalf of the client, and
           * most likely send some data back...but this is a
           * gross oversimplification.
           */
          synchronized(eventSync) {
            bytesRead += bytes;
            eventsToProcess--;
            if (eventsToProcess <= 0) {
              eventSync.notify();
            }
          }
        }
      }
    }
  }
}