Humberto,

Although Flink CEP lacks notFollowedBy at the end of a Pattern, there is a
way to implement this by exploiting the timeout feature.

The Flink training includes an exercise [1] where the objective is to
identify taxi rides with a START event that is not followed by an END event
within two hours. You'll find a solution to this exercise that uses CEP in
[2].

[1] https://training.ververica.com/exercises/longRides.html
[2]
https://github.com/ververica/flink-training-exercises/blob/master/src/main/java/com/ververica/flinktraining/solutions/datastream_java/cep/LongRidesCEPSolution.java

Best,
David



On Thu, Mar 19, 2020 at 4:41 AM Zhijiang <wangzhijiang...@aliyun.com> wrote:

> Hi Humberto,
>
> I guess Fuji is familiar with Flink CEP and he can answer your proposed
> question. I already cc him.
>
> Best,
> Zhijiang
>
> ------------------------------------------------------------------
> From:Humberto Rodriguez Avila <rhumber...@outlook.com>
> Send Time:2020 Mar. 18 (Wed.) 17:31
> To:user <user@flink.apache.org>
> Subject:FlinkCEP - Detect absence of a certain event
>
> In the documentation of FlinkCEP, I found that I can enforce that a
> particular event doesn't occur between two other events using
> notFollowedBy or notNext.
>
> However, I was wondering If I could detect the absence of a certain event
> after a time X. For example, if an event *A* is not followed by another
> event *A* within 10 seconds, fire an alert or do something.
>
> Could be possible to define a FlinkCEP pattern to capture that situation?
>
> Thanks in advance, Humberto
>
>
>

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