replicationmanagerimpl.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.p2p.replication.manager;

import java.util.*;
import java.util.logging.*;

import rice.*;
import rice.Continuation.*;

import rice.environment.Environment;
import rice.environment.logging.Logger;
import rice.environment.params.Parameters;
import rice.p2p.commonapi.*;
import rice.p2p.replication.*;
import rice.p2p.replication.manager.messaging.*;

/**
 * @(#) ReplicationManagerImpl.java This class is the default provided
 * implementation of the replication manager used.
 *
 * @version $Id: ReplicationManagerImpl.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 */
public class ReplicationManagerImpl implements ReplicationManager, ReplicationClient, Application {

  /**
   * The amount of time to wait between fetch calls to the client
   */
  public final int FETCH_DELAY;

  /**
   * The amount of time to wait before giving up on a client fetch
   */
  public final int TIMEOUT_DELAY;

  /**
   * The number of ids to delete at a given time - others will be deleted later
   */
  public final int NUM_DELETE_AT_ONCE;

  /**
   * The id factory used for manipulating ids
   */
  protected IdFactory factory;

  /**
   * The endpoint used for sending reminder messages
   */
  protected Endpoint endpoint;

  /**
   * The replication used by the manager
   */
  protected ReplicationImpl replication;

  /**
   * The client of this manager
   */
  protected ReplicationManagerClient client;

  /**
   * The helper for the replication manager
   */
  protected ReplicationManagerHelper helper;

  /**
   * The deleter, for managing ids to delete
   */
  protected ReplicationManagerDeleter deleter;

  /**
   * DESCRIBE THE FIELD
   */
  protected String instance;

  /**
   * DESCRIBE THE FIELD
   */
  protected Environment environment;

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

  /**
   * Constructor
   *
   * @param node The node below this Replication implementation
   * @param client The client for this Replication
   * @param replicationFactor The replication factor for this instance
   * @param instance The unique instance name of this Replication
   */
  public ReplicationManagerImpl(Node node, ReplicationManagerClient client, int replicationFactor, String instance) {
    this(node, client, replicationFactor, instance, null);
  }

  /**
   * Constructor
   *
   * @param node The node below this Replication implementation
   * @param client The client for this Replication
   * @param replicationFactor The replication factor for this instance
   * @param instance The unique instance name of this Replication
   * @param policy The replication policy to use
   */
  public ReplicationManagerImpl(Node node, ReplicationManagerClient client, int replicationFactor, String instance, ReplicationPolicy policy) {
    this.environment = node.getEnvironment();
    logger = environment.getLogManager().getLogger(ReplicationManagerImpl.class, instance);
    Parameters p = environment.getParameters();

    FETCH_DELAY = p.getInt("p2p_replication_manager_fetch_delay");
    TIMEOUT_DELAY = p.getInt("p2p_replication_manager_timeout_delay");
    NUM_DELETE_AT_ONCE = p.getInt("p2p_replication_manager_num_delete_at_once");

    this.client = client;
    this.factory = node.getIdFactory();
    this.endpoint = node.buildEndpoint(this, instance);
    this.helper = new ReplicationManagerHelper();
    this.deleter = new ReplicationManagerDeleter();
    this.instance = instance;

    if (logger.level <= Logger.FINE) {
      logger.log("Starting up ReplicationManagerImpl with client " + client);
    }

    this.replication = new ReplicationImpl(node, this, replicationFactor, instance, policy);
    endpoint.register();
  }

  // ----- UTILITY METHODS -----

  /**
   * Utility method which returns the underlying replication object. Should only
   * be used for testing - messing with this causes undefined behavior.
   *
   * @return The underlying replication object
   */
  public Replication getReplication() {
    return replication;
  }

  /**
   * This upcall is to notify the application of the range of keys for which it
   * is responsible. The application might choose to react to call by calling a
   * scan(complement of this range) to the persistance manager and get the keys
   * for which it is not responsible and call delete on the persistance manager
   * for those objects.
   *
   * @param range the range of keys for which the local node is currently
   *      responsible
   */
  public void setRange(final IdRange range) {
    if (logger.level <= Logger.FINEST) {
      logger.log("Removing range " + range + " from the list of pending ids");
    }

    helper.setRange(range);
    deleter.setRange(range);
  }


  // ----- INTERNAL METHODS -----

  /**
   * Internal method which clones an IdSet, so that iterators work as expected
   *
   * @param keySet The set to clone
   * @return The cloned set
   */
  protected IdSet clone(IdSet keySet) {
    IdSet result = factory.buildIdSet();
    Iterator i = keySet.getIterator();

    while (i.hasNext()) {
      result.addId((Id) i.next());
    }

    return result;
  }

  /**
   * Internal method which informs the client of the next id to fetch
   *
   * @param id The id which the client should fetch
   * @param hint The hint where the id may be
   */
  protected void informClient(final Id id, NodeHandle hint) {
    if (logger.level <= Logger.FINE) {
      logger.log("Telling client to fetch id " + id);
    }

    final CancellableTask timer = endpoint.scheduleMessage(new TimeoutMessage(id), TIMEOUT_DELAY);

    client.fetch(id, hint,
      new Continuation() {
        public void receiveResult(Object o) {
          if (!(new Boolean(true)).equals(o)) {
            if (o instanceof Throwable) {
              if (logger.level <= Logger.WARNING) {
                logger.logException("Fetching of id " + id + " failed with ", (Throwable) o);
              }
            } else {
              if (logger.level <= Logger.WARNING) {
                logger.log("Fetching of id " + id + " failed with " + o);
              }
            }
          }

          if (logger.level <= Logger.FINE) {
            logger.log("Successfully fetched id " + id);
          }

          timer.cancel();
          helper.message(id);
        }

        public void receiveException(Exception e) {
          receiveResult(e);
        }
      });
  }

  /**
   * Internal method which schedules the next reminder message (if it is
   * necessary), or simply resets the active flag if there's nothing to be
   * fetched.
   */
  protected void scheduleNext() {
    if (logger.level <= Logger.FINER) {
      logger.log("Scheduling next fetch in " + FETCH_DELAY + " milliseconds");
    }

    endpoint.scheduleMessage(new ReminderMessage(), FETCH_DELAY);
  }


  // ----- REPLICATION METHODS -----

  /**
   * This upcall is invoked to notify the application that is should fetch the
   * cooresponding keys in this set, since the node is now responsible for these
   * keys also.
   *
   * @param keySet set containing the keys that needs to be fetched
   * @param hint DESCRIBE THE PARAMETER
   */
  public void fetch(IdSet keySet, NodeHandle hint) {
    // log.finer(endpoint.getId() + ": Adding keyset " + keySet + " to the list of pending ids");
    helper.fetch(keySet, hint);
  }

  /**
   * This upcall should return the set of keys that the application currently
   * stores in this range. Should return a empty IdSet (not null), in the case
   * that no keys belong to this range. In this case, it returns the list of
   * keys the client has, along with the keys which we have yet to tell the
   * client to fetch.
   *
   * @param range the requested range
   * @return DESCRIBE THE RETURN VALUE
   */
  public IdSet scan(IdRange range) {
    return client.scan(range);
  }


  // ----- COMMONAPI METHODS -----

  /**
   * This method is invoked on applications when the underlying node is about to
   * forward the given message with the provided target to the specified next
   * hop. Applications can change the contents of the message, specify a
   * different nextHop (through re-routing), or completely terminate the
   * message.
   *
   * @param message The message being sent, containing an internal message along
   *      with a destination key and nodeHandle next hop.
   * @return Whether or not to forward the message further
   */
  public boolean forward(RouteMessage message) {
    return true;
  }

  /**
   * This method is called on the application at the destination node for the
   * given id.
   *
   * @param id The destination id of the message
   * @param message The message being sent
   */
  public void deliver(Id id, Message message) {
    if (message instanceof ReminderMessage) {
      if (logger.level <= Logger.FINEST) {
        logger.log("Received reminder message");
      }
      helper.wakeup();
    } else if (message instanceof TimeoutMessage) {
      if (logger.level <= Logger.FINEST) {
        logger.log("Received timeout message");
      }
      helper.message(((TimeoutMessage) message).getId());
    } else {
      if (logger.level <= Logger.WARNING) {
        logger.log("Received unknown message " + message);
      }
    }
  }