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From Chengzhi Zhao <w.zhaocheng...@gmail.com>
Subject Re: Multiple Streams Connect Watermark
Date Thu, 26 Apr 2018 18:44:10 GMT
Thanks Fabian for the explanation.

If I have data with different schemas, it seems the only option I have is
to use connect to perform joins (inner, outer), is there any operators that
can put more than two streams together (all different schema)?


On Thu, Apr 26, 2018 at 6:05 AM, Fabian Hueske <fhueske@gmail.com> wrote:

> Hi Chengzhi,
> Functions in Flink are implemented in a way to preserve the timestamps of
> elements or assign timestamps which are aligned with the existing
> watermarks.
> For example, the result of a time window aggregation has the end timestamp
> of the window as a timestamp and records emitted by the onTimer() method
> have the timestamp of the timer as a record timestamp.
> So unless you fiddle with internal APIs to reset the record timestamps of
> elements, you don't need to worry about generating new watermarks.
> Best, Fabian
> 2018-04-25 20:20 GMT+02:00 Chengzhi Zhao <w.zhaochengzhi@gmail.com>:
>> Hi, everyone,
>> I am trying to do some join-like pipeline using flink connect operator
>> and CoProcessFunction, I have use case that I need to connect 3+ streams.
>> So I am having something like this:
>> A
>>     ===> C
>> B                 ==> E
>>               D
>> So two streams A and B connect at first with 3 hours late on low
>> watermark, after data has been emitted (the output C stream), a new stream
>> D connect to C and emitted E as final output. I was wondering how the
>> downstream watermark should be defined. Should I give C stream a new
>> watermark for 3 hours delay again? or when I connect stream D, everything
>> will be 6 hours late on low watermark.
>> I am using BoundedOutOfOrdernessGenerator[1] with maxOutOfOrderness 3
>> hours
>> Thanks for your tips and help in advance.
>> Best,
>> Chengzhi
>> [1]https://ci.apache.org/projects/flink/flink-docs-release-
>> 1.4/dev/event_timestamps_watermarks.html#with-periodic-watermarks

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