[jira] [Commented] (APEXCORE-60) Iterative processing support

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/APEXCORE-60?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15081449#comment-15081449 ] 

ASF GitHub Bot commented on APEXCORE-60:
----------------------------------------

Github user sandeshh commented on a diff in the pull request:

    https://github.com/apache/incubator-apex-core/pull/185#discussion_r48757578
  
    --- Diff: api/src/main/java/com/datatorrent/api/Operator.java ---
    @@ -99,6 +99,25 @@ public String toString()
       }
     
       /**
    +   * DelayOperator is an operator of which the outgoing streaming window id is incremented by *one* by the
    +   * engine, thus allowing loops in the "DAG". The output ports of a DelayOperator, if connected, *must*
    +   * immediately connect to an upstream operator in the data flow path. Note that at least one output port of
    +   * DelayOperator should be connected in order for the DelayOperator to serve its purpose.
    +   *
    +   * This is meant for iterative algorithms in the topology. A larger window increment can be simulated by an
    +   * implementation of this interface.
    +   */
    +  interface DelayOperator extends Operator
    +  {
    +    /**
    +     * This method gets called at the first window of the execution.
    +     * The implementation is expected to emit tuples for initialization and/or
    +     * recovery.
    +     */
    +    void firstWindow();
    --- End diff --
    
    Should this function have "Window ID" as an argument?


> Iterative processing support
> ----------------------------
>
>                 Key: APEXCORE-60
>                 URL: https://issues.apache.org/jira/browse/APEXCORE-60
>             Project: Apache Apex Core
>          Issue Type: New Feature
>            Reporter: David Yan
>            Assignee: David Yan
>              Labels: roadmap
>             Fix For: 3.3.0
>
>
> We would like to support iterative processing by introducing cycles in the graph (known as DAG now, but no longer if we support iterative processing).
> Initial idea is as follow:
> {noformat}
>      |----|
>      v    |
> A -> B -> C -> D
> ^         |
> |---------|
> {noformat} 
> C has two separate backward streams to A and B.  The input ports of A and B that C connects to will have a special attribute on how many window IDs ahead the incoming windows should be treated as, and A and B will be responsible for the initial data for such input ports.
> Another idea is to have C advance the window ID on its output ports and have C generate the initial data on its output ports to A and B.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)