flink-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Gyula Fóra <gyula.f...@gmail.com>
Subject Re: Event time in Flink streaming
Date Tue, 08 Sep 2015 19:53:38 GMT
This is actually simpler than you think, you can just use the Time.of(...)

ds.window(Time.of(long windowSize, Timestamp yourTimeStampExtractor, long


Martin Neumann <mneumann@sics.se> ezt írta (időpont: 2015. szept. 8., K,

> Hej,
> I want to give TimeTriggerPolicy a try and see how much of a problem it
> will be in this use case. Is there any example on how to use it? I looked
> at the API descriptions but I'm confused now.
> cheers Martin
> On Fri, Aug 28, 2015 at 5:35 PM, Martin Neumann <mneumann@sics.se> wrote:
>> The stream consists of logs from different machines with synchronized
>> clocks. As a result timestamps are not strictly increasing but there is a
>> bound on how much out of order they can be. (One aim is to detect events go
>> out of order more then a certain amount indication some problem in the
>> system setup)
>> I will look at the example policies and see if I can find a way to make
>> it work with 0.9.
>> I am aware of Google Dataflow and the discussion on Flink, though I just
>> recently learned more about the field, so I didn't have to much useful to
>> say. This might change if I get some more experience with the usecase I'm
>> working on.
>> cheers Martin
>> On Fri, Aug 28, 2015 at 5:06 PM, Aljoscha Krettek <aljoscha@apache.org>
>> wrote:
>>> Hi Martin,
>>> the answer depends, because the current windowing implementation has
>>> some problems. We are working on improving it in the 0.10 release, though.
>>> If your elements arrive with strictly increasing timestamps and you have
>>> parallelism=1 or don't perform any re-partitioning of data (which a
>>> groupBy() does, for example) then what Matthias proposed works for you. If
>>> not then you can get intro problems with out-of-order elements and windows
>>> will be incorrectly determined.
>>> If you are interested in what we are working on for 0.10, please look at
>>> the design documents here
>>> https://cwiki.apache.org/confluence/display/FLINK/Streams+and+Operations+on+Streams
>>> here
>>> https://cwiki.apache.org/confluence/display/FLINK/Time+and+Order+in+Streams.
>>> The basic idea is to make windows work correctly when elements arrive not
>>> ordered by timestamps. For this we want use watermarks as popularized, for
>>> example, by Google Dataflow.
>>> Please ask if you have questions about this or are interested in joining
>>> the discussion (the design as not yet finalized, both API and
>>> implementation). :D
>>> Cheers,
>>> Aljoscha
>>> P.S. I have some proof-of-concept work in a branch of mine, if you
>>> interested in my work there I could give you access to it.
>>> On Fri, 28 Aug 2015 at 16:11 Matthias J. Sax <
>>> mjsax@informatik.hu-berlin.de> wrote:
>>>> Hi Martin,
>>>> you need to implement you own policy. However, this should be be
>>>> complicated. Have a look at "TimeTriggerPolicy". You just need to
>>>> provide a "Timestamp" implementation that extracts you ts-attribute from
>>>> the tuples.
>>>> -Matthias
>>>> On 08/28/2015 03:58 PM, Martin Neumann wrote:
>>>> > Hej,
>>>> >
>>>> > I have a stream of timestamped events I want to process in Flink
>>>> streaming.
>>>> > Di I have to write my own policies to do so, or can define time based
>>>> > windows to use the timestamps instead of the system time?
>>>> >
>>>> > cheers Martin

View raw message