[jira] [Commented] (HAMA-567) BSPPeer should provide means for chaining supersteps to share data among them.

["Suraj Menon (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HAMA-567?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13266850#comment-13266850 ] 

Suraj Menon commented on HAMA-567:
----------------------------------

Let me know if the following API access in BSPPeer is enough and named correctly? Shall we add this in 0.5 release, considering it is a simple change of adding a Map<String, Object> and would be needed for anyone who uses Superstep class. Checkpointing can be added for the next release. 

{code}

  /**
   * Save object in peer for future reference. This could be used by 
   * sequence of supersteps. If there is already an object saved under the key, 
   * calling this function overwrites the object for the key. 
   * @param token The String value that should be used as key to save object.
   * @param value The object to be saved for the key.
   */
  public void save(String token, Object value);

  /**
   * Returns true if there is already an object saved for the key.
   * @param token The key for which we check if there is already an object 
   * present.
   * @return Return true if object is present for the key.
   */
  public boolean isObjectPresentFor(String token);

  /**
   * Returns the object saved for the key.
   * @param token The key for which an object is to be retrieved.
   * @return object The object saved with the key. If the key is not present 
   * the function returns null.
   */
  public Object getSavedObject(String token);
{code}
                
> BSPPeer should provide means for chaining supersteps to share data among them.
> ------------------------------------------------------------------------------
>
>                 Key: HAMA-567
>                 URL: https://issues.apache.org/jira/browse/HAMA-567
>             Project: Hama
>          Issue Type: Improvement
>          Components: bsp core
>    Affects Versions: 0.6.0
>            Reporter: Suraj Menon
>             Fix For: 0.6.0
>
>
> In most scenarios, a superstep would need certain values or objects that were computed in the previous superstep. When using the chaining Superstep design to implement BSP algorithms, this gets a little ugly/difficult to implement. BSPPeer should provide means (preferably a map<String,Object>) so that the next Superstep can ask for the values in previous superstep using String token to query the map. Also, this map could be checkpointed periodically in the background so that we can completely recover the state of a task after failure. The BSPPeer object should have a dedicated get and set function for updating values in the peer.

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