i2p.i2p/apps/i2psnark/java/src/org/klomp/snark/PeerCheckerTask.java

/* PeerCheckTasks - TimerTask that checks for good/bad up/downloaders.
   Copyright (C) 2003 Mark J. Wielaard

   This file is part of Snark.
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.
 
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
 
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/

package org.klomp.snark;

import java.util.*;

/**
 * TimerTask that checks for good/bad up/downloader. Works together
 * with the PeerCoordinator to select which Peers get (un)choked.
 */
class PeerCheckerTask extends TimerTask
{
  private final long KILOPERSECOND = 1024*(PeerCoordinator.CHECK_PERIOD/1000);

  private final PeerCoordinator coordinator;

  PeerCheckerTask(PeerCoordinator coordinator)
  {
    this.coordinator = coordinator;
  }

  public void run()
  {
    synchronized(coordinator.peers)
      {
        // Calculate total uploading and worst downloader.
        long worstdownload = Long.MAX_VALUE;
        Peer worstDownloader = null;

        int peers = 0;
        int uploaders = 0;
        int downloaders = 0;
        int interested = 0;
        int interesting = 0;
        int choking = 0;
        int choked = 0;

        long uploaded = 0;
        long downloaded = 0;

        // Keep track of peers we remove now,
        // we will add them back to the end of the list.
        List removed = new ArrayList();

        Iterator it = coordinator.peers.iterator();
        while (it.hasNext())
          {
            Peer peer = (Peer)it.next();

            // Remove dying peers
            if (!peer.isConnected())
              {
                it.remove();
                coordinator.removePeerFromPieces(peer);
                continue;
              }

            peers++;

            if (!peer.isChoking())
              uploaders++;
            if (!peer.isChoked() && peer.isInteresting())
              downloaders++;
            if (peer.isInterested())
              interested++;
            if (peer.isInteresting())
              interesting++;
            if (peer.isChoking())
              choking++;
            if (peer.isChoked())
              choked++;

            // XXX - We should calculate the up/download rate a bit
            // more intelligently
            long upload = peer.getUploaded();
            uploaded += upload;
            long download = peer.getDownloaded();
            downloaded += download;
            peer.resetCounters();

            if (Snark.debug >= Snark.DEBUG)
              {
                Snark.debug(peer + ":", Snark.DEBUG);
                Snark.debug(" ul: " + upload/KILOPERSECOND
                            + " dl: " + download/KILOPERSECOND
                            + " i: " + peer.isInterested()
                            + " I: " + peer.isInteresting()
                            + " c: " + peer.isChoking()
                            + " C: " + peer.isChoked(),
                            Snark.DEBUG);
              }

            // If we are at our max uploaders and we have lots of other
            // interested peers try to make some room.
            // (Note use of coordinator.uploaders)
            if (coordinator.uploaders >= PeerCoordinator.MAX_UPLOADERS
                && interested > PeerCoordinator.MAX_UPLOADERS
                && !peer.isChoking())
              {
                // Check if it still wants pieces from us.
                if (!peer.isInterested())
                  {
                    if (Snark.debug >= Snark.INFO)
                      Snark.debug("Choke uninterested peer: " + peer,
                                  Snark.INFO);
                    peer.setChoking(true);
                    uploaders--;
                    coordinator.uploaders--;
                    
                    // Put it at the back of the list
                    it.remove();
                    removed.add(peer);
                  }
                else if (peer.isChoked())
                  {
                    // If they are choking us make someone else a downloader
                    if (Snark.debug >= Snark.DEBUG)
                      Snark.debug("Choke choking peer: " + peer, Snark.DEBUG);
                    peer.setChoking(true);
                    uploaders--;
                    coordinator.uploaders--;
                    
                    // Put it at the back of the list
                    it.remove();
                    removed.add(peer);
                  }
                else if (peer.isInteresting()
                         && !peer.isChoked()
                         && download == 0)
                  {
                    // We are downloading but didn't receive anything...
                    if (Snark.debug >= Snark.DEBUG)
                      Snark.debug("Choke downloader that doesn't deliver:"
                                  + peer, Snark.DEBUG);
                    peer.setChoking(true);
                    uploaders--;
                    coordinator.uploaders--;
                    
                    // Put it at the back of the list
                    it.remove();
                    removed.add(peer);
                  }
                else if (!peer.isChoking() && download < worstdownload)
                  {
                    // Make sure download is good if we are uploading
                    worstdownload = download;
                    worstDownloader = peer;
                  }
              }
          }

        // Resync actual uploaders value
        // (can shift a bit by disconnecting peers)
        coordinator.uploaders = uploaders;

        // Remove the worst downloader if needed.
        if (uploaders >= PeerCoordinator.MAX_UPLOADERS
            && interested > PeerCoordinator.MAX_UPLOADERS
            && worstDownloader != null)
          {
            if (Snark.debug >= Snark.DEBUG)
              Snark.debug("Choke worst downloader: " + worstDownloader,
                          Snark.DEBUG);

            worstDownloader.setChoking(true);
            coordinator.uploaders--;

            // Put it at the back of the list
            coordinator.peers.remove(worstDownloader);
            removed.add(worstDownloader);
          }
        
        // Optimistically unchoke a peer
        coordinator.unchokePeer();

        // Put peers back at the end of the list that we removed earlier.
        coordinator.peers.addAll(removed);
      }
  }
}