Re: Incremental state with purging

Posted by Congxian Qiu on May 15, 2020; 9:14am
URL: http://deprecated-apache-flink-user-mailing-list-archive.369.s1.nabble.com/Incremental-state-with-purging-tp35090p35153.html

Hi

From your description,  you want to do two things:

1 update state and remote the state older than x

2 output the state every y second

From my side, the first can be done by using TTL state as Yun said,

the second can be done by using KeyedProcessFunction[1]

If you want to have complex logic to remove the older state in step 1, maybe you can also use the KeyedProcessFunction and timer()

[1] https://ci.apache.org/projects/flink/flink-docs-release-1.10/dev/stream/operators/process_function.html#the-keyedprocessfunction

Yun Tang <[hidden email]> 于2020年5月13日周三 下午7:42写道：

Hi

From your description: "output the state every y seconds and remove old elements", I think TTL [1] is the proper solution for your scenario. And you could define the ttl of your state as y seconds so that processfunction could only print elements in the last y seconds.

[1] https://ci.apache.org/projects/flink/flink-docs-stable/dev/stream/state/state.html#state-time-to-live-ttl

Best

Yun Tang

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From: Annemarie Burger <[hidden email]>
Sent: Wednesday, May 13, 2020 2:46
To: [hidden email] <[hidden email]>
Subject: Incremental state with purging

 

Hi,

I'm trying to implement the most efficient way to incrementally put incoming
DataStream elements in my (map)state, while removing old elements (older
that x) from that same state. I then want to output the state every y
seconds. I've looked into using the ProcessFunction with onTimer, or
building my own Trigger for a window function, but I struggle with putting
all this together in a logical and efficient way. Since the state is very
big I don't want to duplicate it over multiple (sliding)windows. Does
anybody know the best way to achieve this? Some pseudo code would be very
helpful.

Thanks!



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