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From Ufuk Celebi <...@apache.org>
Subject Re: Checkpoint
Date Thu, 10 Mar 2016 09:44:49 GMT
How many vertices does the web interface show and what parallelism are
you running? If the sleeping operator is chained you will not see
anything.

If your goal is to just see some back pressure warning, you can call
env.disableOperatorChaining() and re-run the program. Does this work?

– Ufuk


On Thu, Mar 10, 2016 at 1:35 AM, Vijay Srinivasaraghavan
<vijikarthi@yahoo.com> wrote:
> Hi Ufuk,
>
> I have increased the sampling size to 1000 and decreased the refresh
> interval by half. In my Kafka topic I have pumped million messages which is
> read by KafkaConsumer pipeline and then pass it to a transofmation step
> where I have introduced sleep (3 sec) for every single message received and
> the final step is HDFS sink using RollingSinc API.
>
> jobmanager.web.backpressure.num-samples: 1000
> jobmanager.web.backpressure.refresh-interval: 30000
>
>
> I was hoping to see the backpressure tab from UI to display some warning but
> I still see "OK" message.
>
> This makes me wonder if I am testing the backpressure scenario properly or
> not?
>
> Regards
> Vijay
>
> On Monday, March 7, 2016 3:19 PM, Ufuk Celebi <uce@apache.org> wrote:
>
>
> Hey Vijay!
>
> On Mon, Mar 7, 2016 at 8:42 PM, Vijay Srinivasaraghavan
> <vijikarthi@yahoo.com> wrote:
>> 3) How can I simulate and verify backpressure? I have introduced some
>> delay
>> (Thread Sleep) in the job before the sink but the "backpressure" tab from
>> UI
>> does not show any indication of whether backpressure is working or not.
>
> If a task is slow, it is back pressuring upstream tasks, e.g. if your
> transformations have the sleep, the sources should be back pressured.
> It can happen that even with the sleep the tasks still produce their
> data as fast as they can and hence no back pressure is indicated in
> the web interface. You can increase the sleep to check this.
>
> The mechanism used to determine back pressure is based on sampling the
> stack traces of running tasks. You can increase the number of samples
> and/or decrease the delay between samples via config parameters shown
> in [1]. It can happen that the samples miss the back pressure
> indicators, but usually the defaults work fine.
>
>
> [1]
> https://ci.apache.org/projects/flink/flink-docs-master/setup/config.html#jobmanager-web-frontend
>
>
>

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