standardroutesetprotocol.java

pastry的java实现的2.0b版

/*************************************************************************

"FreePastry" Peer-to-Peer Application Development Substrate 

Copyright 2002, Rice University. All rights reserved.

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********************************************************************************/
package rice.pastry.standard;

import rice.environment.Environment;
import rice.environment.logging.Logger;
import rice.p2p.commonapi.rawserialization.*;
import rice.pastry.*;
import rice.pastry.client.PastryAppl;
import rice.pastry.messaging.*;
import rice.pastry.routing.*;

import java.io.IOException;
import java.util.*;

/**
 * An implementation of a simple route set protocol.
 *
 * @version $Id: StandardRouteSetProtocol.java,v 1.15 2005/03/11 00:58:02 jeffh
 *      Exp $
 * @author Andrew Ladd
 * @author Peter Druschel
 */

public class StandardRouteSetProtocol extends PastryAppl {
  private final int maxTrials;

  private RoutingTable routeTable;

  private Environment environmet;

  /**
   * DESCRIBE THE FIELD
   */
  protected Logger logger;

  /**
   * Constructor.
   *
   * @param rt the routing table
   * @param ln DESCRIBE THE PARAMETER
   * @param env DESCRIBE THE PARAMETER
   */
  public StandardRouteSetProtocol(PastryNode ln, RoutingTable rt, Environment env) {
    this(ln, rt, env, null);
  }

  /**
   * Constructor for StandardRouteSetProtocol.
   *
   * @param ln DESCRIBE THE PARAMETER
   * @param rt DESCRIBE THE PARAMETER
   * @param env DESCRIBE THE PARAMETER
   * @param md DESCRIBE THE PARAMETER
   */
  public StandardRouteSetProtocol(PastryNode ln, RoutingTable rt, Environment env, MessageDeserializer md) {
    super(ln, null, RouteProtocolAddress.getCode(), md == null ? new SRSPDeserializer(ln) : md);
    this.environmet = env;
    maxTrials = (1 << rt.baseBitLength()) / 2;
    routeTable = rt;
    logger = env.getLogManager().getLogger(getClass(), null);
  }

  /**
   * Receives a message.
   *
   * @param msg the message.
   */

  public void messageForAppl(Message msg) {
    if (msg instanceof BroadcastRouteRow) {
      BroadcastRouteRow brr = (BroadcastRouteRow) msg;

      RouteSet[] row = brr.getRow();

      NodeHandle nh = brr.from();
      if (nh.isAlive()) {
        routeTable.put(nh);
      }

      for (int i = 0; i < row.length; i++) {
        RouteSet rs = row[i];

        for (int j = 0; rs != null && j < rs.size(); j++) {
          nh = rs.get(j);
          if (nh.isAlive() == false) {
            continue;
          }
          routeTable.put(nh);
        }
      }
    } else if (msg instanceof RequestRouteRow) {
      // a remote node request one of
      // our routeTable rows
      RequestRouteRow rrr = (RequestRouteRow) msg;

      int reqRow = rrr.getRow();
      NodeHandle nh = rrr.returnHandle();

      RouteSet row[] = routeTable.getRow(reqRow);
      BroadcastRouteRow brr = new BroadcastRouteRow(thePastryNode.getLocalHandle(), row);
      nh.receiveMessage(brr);
    } else if (msg instanceof InitiateRouteSetMaintenance) {
      // request for
      // routing table
      // maintenance

      // perform routing table maintenance
      maintainRouteSet();

    } else {
      throw new Error(
        "StandardRouteSetProtocol: received message is of unknown type");
    }

  }

  /**
   * performs periodic maintenance of the routing table for each populated row
   * of the routing table, it picks a random column and swaps routing table rows
   * with the closest entry in that column
   */

  private void maintainRouteSet() {

    if (logger.level <= Logger.FINE) {
      logger.log(
        "maintainRouteSet " + thePastryNode.getLocalHandle().getNodeId());
    }

    // for each populated row in our routing table
    for (byte i = (byte) (routeTable.numRows() - 1); i >= 0; i--) {
      RouteSet row[] = routeTable.getRow(i);
      BroadcastRouteRow brr = new BroadcastRouteRow(thePastryNode.getLocalHandle(), row);
      RequestRouteRow rrr = new RequestRouteRow(thePastryNode.getLocalHandle(), i);
      int myCol = thePastryNode.getLocalHandle().getNodeId().getDigit(i,
        routeTable.baseBitLength());
      int j;

      // try up to maxTrials times to find a column with live entries
      for (j = 0; j < maxTrials; j++) {
        // pick a random column
        int col = environmet.getRandomSource().nextInt(routeTable.numColumns());
        if (col == myCol) {
          continue;
        }

        RouteSet rs = row[col];

        // swap row with closest node only
        NodeHandle nh;

        if (rs != null && (nh = rs.closestNode()) != null) {
          nh.receiveMessage(brr);
          nh.receiveMessage(rrr);
          break;
        }
      }

      // once we hit a row where we can't find a populated entry after numTrial
      // trials, we finish
      if (j == maxTrials) {
        break;
      }
    }

  }

  /**
   * DESCRIBE THE METHOD
   *
   * @return DESCRIBE THE RETURN VALUE
   */
  public boolean deliverWhenNotReady() {
    return true;
  }

  /**
   * DESCRIBE THE CLASS
   *
   * @version $Id: pretty.settings 2305 2005-03-11 20:22:33Z jeffh $
   * @author jeffh
   */
  static class SRSPDeserializer extends PJavaSerializedDeserializer {
    /**
     * Constructor for SRSPDeserializer.
     *
     * @param pn DESCRIBE THE PARAMETER
     */
    public SRSPDeserializer(PastryNode pn) {
      super(pn);
    }

    /**
     * DESCRIBE THE METHOD
     *
     * @param buf DESCRIBE THE PARAMETER
     * @param type DESCRIBE THE PARAMETER
     * @param priority DESCRIBE THE PARAMETER
     * @param sender DESCRIBE THE PARAMETER
     * @return DESCRIBE THE RETURN VALUE
     * @exception IOException DESCRIBE THE EXCEPTION
     */
    public Message deserialize(InputBuffer buf, short type, byte priority, NodeHandle sender) throws IOException {
      switch (type) {
        case RequestRouteRow.TYPE:
          return new RequestRouteRow(sender, buf);
        case BroadcastRouteRow.TYPE:
          return new BroadcastRouteRow(buf, pn);
      }
      return null;
    }
  }

}