Thanks Fabian and Aljoscha, I try to implement the trigger as you described as follow:
https://gist.github.com/anonymous/d0578a4d27768a75bea4 <https://gist.github.com/anonymous/d0578a4d27768a75bea4> It works fine , indeed. Thanks, Anwar On Fri, Nov 27, 2015 at 11:49 AM, Aljoscha Krettek <aljos...@apache.org> wrote: > Hi Anwar, > what Fabian wrote is completely right. I just want to give the reasoning > for why the CountTrigger behaves as it does. The idea was to have Triggers > that clearly focus on one thing and then at some point add combination > triggers. For example, an OrTrigger that triggers if either of it’s sub > triggers triggers, or an AndTrigger that triggers after both its sub > triggers fire. (There is also more complex stuff that could be thought of > here.) > > Cheers, > Aljoscha > > On 27 Nov 2015, at 09:59, fhue...@gmail.com wrote: > > > > > > Hi, > > > > a regular tumbling time window of 5 seconds gets all elements within > that period of time (semantics of time varies for processing, ingestion, > and event time modes) and triggers the execution after 5 seconds. > > > > If you define a custom trigger, the assignment policy remains the same, > but the trigger condition is overwritten (it is NOT additional but replaces > the default condition), i.e., in your implementation, it will only trigger > when 100 elements arrived. In order to trigger also when the window time > expires, you have to register a timer (processing time or event time timer) > via the trigger context. > > NOTE: The window assigner will continue to assign elements to the > window, even if the window was already evaluated. If you PURGE the window > and an element arrives after that, a new window is created. > > > > To implement your trigger, you have to register a timer in the onEvent() > method with: > > ctx.registerEventTimeTimer(window.getEnd) > > You can to that in every onEvent() call, because the timer is always > overwritten. > > > > NOTE: you should use Flink’s keyed-state (access via triggerContext) if > you want to keep state such as the current count. > > > > Hope this helps. Please let me know if you have further questions. > > Fabian > > > > > > > > > > From: Matthias J. Sax > > Sent: Friday, November 27, 2015 08:44 > > To: user@flink.apache.org > > Subject: Re: Doubt about window and count trigger > > > > > > Hi, > > > > a Trigger is an *additional* condition for intermediate (early) > > evaluation of the window. Thus, it is not "or-ed" to the basic window > > definition. > > > > If you want to have an or-ed window condition, you can customize it by > > specifying your own window definition. > > > > > dataStream.window(new MyOwnWindow() extends WindowAssigner { /* put > your code here */ ); > > > > -Matthias > > > > > > On 11/26/2015 11:40 PM, Anwar Rizal wrote: > > > Hi all, > > > > > > From the documentation: > > > "The |Trigger| specifies when the function that comes after the window > > > clause (e.g., |sum|, |count|) is evaluated (“fires”) for each window." > > > > > > So, basically, if I specify: > > > > > > |keyedStream > > > .window(TumblingTimeWindows.of(Time.of(5, TimeUnit.SECONDS)) > > > .trigger(CountTrigger.of(100))| > > > > > > | > > > | > > > > > > |The execution of the window function is triggered when the count > reaches 100 in the time window of 5 seconds. If you have a system that > never reaches 100 in 5 seconds, basically you will never have the window > fired.| > > > > > > | > > > | > > > > > > |My question is, what would be the best option to have behavior as > follow:| > > > > > > |The execution of the window function is triggered when 5 seconds is > reached or 100 events are received before 5 seconds.| > > > > > > > > > I think of implementing my own trigger that looks like CountTrigger, > but that will fire also when the end of time window is reached (at the > moment, it just returns Continue, instead of Fired). But maybe there's a > better way ? > > > > > > Is there a reason why CountTrigger is implemented as it is implemented > today, and not as I described above (5 seconds or 100 events reached, > whichever comes first). > > > > > > > > > Thanks, > > > > > > Anwar. > > > > >
