past.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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This software is provided by RICE and the contributors on an "as is"
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********************************************************************************/

package rice.p2p.past;

import rice.*;
import rice.environment.Environment;
import rice.p2p.commonapi.*;
import rice.p2p.past.rawserialization.*;

/**
 * @(#) Past.java This interface is exported by all instances of Past. An
 * instance of Past provides a distributed hash table (DHT) service. Each
 * instance stores tuples consisting of a key and an object of a particular
 * type, which must implement the interface PastContent. Past is event-driven,
 * so all methods are asynchronous and receive their results using the command
 * pattern.
 *
 * @version $Id: Past.java 3274 2006-05-15 16:17:47Z jeffh $
 * @author Alan Mislove
 * @author Ansley Post
 * @author Peter Druschel
 */
public interface Past {

  /**
   * Inserts an object with the given ID into this instance of Past.
   * Asynchronously returns a PastException to command, if the operation was
   * unsuccessful. If the operation was successful, a Boolean[] is returned
   * representing the responses from each of the replicas which inserted the
   * object.
   *
   * @param obj the object to be inserted
   * @param command Command to be performed when the result is received
   */
  public void insert(PastContent obj, Continuation command);

  /**
   * Retrieves the object stored in this instance of Past with the given ID.
   * Asynchronously returns a PastContent object as the result to the provided
   * Continuation, or a PastException. This method is provided for convenience;
   * its effect is identical to a lookupHandles() and a subsequent fetch() to
   * the handle that is nearest in the network. The client must authenticate the
   * object. In case of failure, an alternate replica of the object can be
   * obtained via lookupHandles() and fetch(). This method is not safe if the
   * object is immutable and storage nodes are not trusted. In this case,
   * clients should used the lookUpHandles method to obtains the handles of all
   * primary replicas and determine which replica is fresh in an
   * application-specific manner. By default, this method attempts to cache the
   * result locally for future use. Applications which do not desire this
   * behavior should use the lookup(id, boolean, command) method.
   *
   * @param id the key to be queried
   * @param command Command to be performed when the result is received
   */
  public void lookup(Id id, Continuation command);

  /**
   * Retrieves the object stored in this instance of Past with the given ID.
   * Asynchronously returns a PastContent object as the result to the provided
   * Continuation, or a PastException. This method is provided for convenience;
   * its effect is identical to a lookupHandles() and a subsequent fetch() to
   * the handle that is nearest in the network. The client must authenticate the
   * object. In case of failure, an alternate replica of the object can be
   * obtained via lookupHandles() and fetch(). This method is not safe if the
   * object is immutable and storage nodes are not trusted. In this case,
   * clients should used the lookUpHandles method to obtains the handles of all
   * primary replicas and determine which replica is fresh in an
   * application-specific manner. This method also allows applications to
   * specify if the result should be cached locally.
   *
   * @param id the key to be queried
   * @param cache Whether or not the result should be cached
   * @param command Command to be performed when the result is received
   */
  public void lookup(Id id, boolean cache, Continuation command);

  /**
   * Retrieves the handles of up to max replicas of the object stored in this
   * instance of Past with the given ID. Asynchronously returns an array of
   * PastContentHandles as the result to the provided Continuation, or a
   * PastException. Each replica handle is obtained from a different primary
   * storage root for the the given key. If max exceeds the replication factor r
   * of this Past instance, only r replicas are returned. This method will
   * return a PastContentHandle[] array containing all of the handles.
   *
   * @param id the key to be queried
   * @param max the maximal number of replicas requested
   * @param command Command to be performed when the result is received
   */
  public void lookupHandles(Id id, int max, Continuation command);

  /**
   * Retrieves the handle for the given object stored on the requested node.
   * Asynchronously returns a PostContentHandle (or null) to the provided
   * continuation.
   *
   * @param id the key to be queried
   * @param handle The node on which the handle is requested
   * @param command Command to be performed when the result is received
   */
  public void lookupHandle(Id id, NodeHandle handle, Continuation command);

  /**
   * Retrieves the object associated with a given content handle. Asynchronously
   * returns a PastContent object as the result to the provided Continuation, or
   * a PastException. The client must authenticate the object. In case of
   * failure, an alternate replica can be obtained using a different handle
   * obtained via lookupHandles().
   *
   * @param handle the key to be queried
   * @param command Command to be performed when the result is received
   */
  public void fetch(PastContentHandle handle, Continuation command);

  /**
   * get the nodeHandle of the local Past node
   *
   * @return the nodehandle
   */
  public NodeHandle getLocalNodeHandle();

  /**
   * Returns the number of replicas used in this Past
   *
   * @return the number of replicas for each object
   */
  public int getReplicationFactor();

  /**
   * Gets the Environment attribute of the Past object
   *
   * @return The Environment value
   */
  public Environment getEnvironment();

  /**
   * @return
   */
  public String getInstance();

  /**
   * Sets the ContentDeserializer attribute of the Past object
   *
   * @param deserializer The new ContentDeserializer value
   */
  public void setContentDeserializer(PastContentDeserializer deserializer);

  /**
   * Sets the ContentHandleDeserializer attribute of the Past object
   *
   * @param deserializer The new ContentHandleDeserializer value
   */
  public void setContentHandleDeserializer(PastContentHandleDeserializer deserializer);

}