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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (QUARKS-230) Add timer triggered window aggregations
Date Fri, 15 Jul 2016 22:35:20 GMT

    [ https://issues.apache.org/jira/browse/QUARKS-230?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15380241#comment-15380241
] 

ASF GitHub Bot commented on QUARKS-230:
---------------------------------------

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

    https://github.com/apache/incubator-quarks/pull/167#discussion_r71049736
  
    --- Diff: api/topology/src/main/java/quarks/topology/TWindow.java ---
    @@ -105,8 +129,85 @@ Licensed to the Apache Software Foundation (ASF) under one
          * @return A stream that contains the latest aggregations of partitions in this window.
          */
         <U> TStream<U> batch(BiFunction<List<T>, K, U> batcher);
    +
    +    /**
    +     * Declares a stream that is a continuous, sliding, 
    +     * timer triggered aggregation of
    +     * partitions in this window.
    +     * <P>
    +     * Periodically trigger an invocation of
    +     * {@code aggregator.apply(tuples, key)}, where {@code tuples} is
    +     * a {@code List<T>} containing all the tuples in the partition in
    +     * insertion order from oldest to newest.  The list is stable
    +     * during the aggregator invocation.  
    +     * The list will be empty if the partition is empty.
    +     * </P>
    +     * <P> 
    +     * A non-null {@code aggregator} result is added to the returned stream.
    +     * </P>
    +     * <P>
    +     * Thus the returned stream will contain a sequence of tuples where the
    +     * most recent tuple represents the most up to date aggregation of a
    +     * partition.
    +     *
    +     * @param <U> Tuple type
    +     * @param period how often to invoke the aggregator
    +     * @param unit TimeUnit for {@code period}
    +     * @param aggregator
    +     *            Logic to aggregation a partition.
    +     * @return A stream that contains the latest aggregations of partitions in this window.
    +     * 
    +     * @see #aggregate(BiFunction)
    +     */
    +    <U> TStream<U> timedAggregate(long period, TimeUnit unit, BiFunction<List<T>,
K, U> aggregator);
    --- End diff --
    
    I was wondering if the continue sending updates even if nothing has changed might be better
handled by a separate operation, then it could be applied to anything, rather than just a
window.
    
    Something like pass any input tuple to the output, but send the last tuple if nothing
has been received for the declared period.


> Add timer triggered window aggregations
> ---------------------------------------
>
>                 Key: QUARKS-230
>                 URL: https://issues.apache.org/jira/browse/QUARKS-230
>             Project: Quarks
>          Issue Type: New Feature
>            Reporter: Dale LaBossiere
>            Assignee: Dale LaBossiere
>
> A recent use case involved the desire for "timer triggered" instead of "partition content
change triggered" window aggregations.  E.g., "I want to trigger an aggregation every second
over the last 10 tuples in a window partition" -- a count-based window with timer triggered
aggregations.
> I propose adding 3 methods to TWindow.  Two in direct support of "timer triggered" aggregations
(this processing model seems like it could be common enough to warrant making it conveniently
available) and one to make it easier to use the lower level Window API to define and use other
processing models.
> I'm submitting a PR with the details for review but the net is these additions to TWindow:
> ```
>     <U> TStream<U> timedAggregate(long period, TimeUnit unit, BiFunction<List<T>,
K, U> aggregator);
>     <U> TStream<U> timedBatch(long period, TimeUnit unit, BiFunction<List<T>,
K, U> batcher);
>     <U, L extends List<T>> TStream<U> process(Window<T,K,L> window,
BiFunction<List<T>, K, U> aggregator);
> ```
> See https://github.com/apache/incubator-quarks/pull/167



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