检测不存在某个事件 [英] Detect absence of a certain event

问题描述

在FlinkCEP的文档中，我发现可以强制使用 notFollowedBy 或 notNext 在其他两个事件之间不发生特定事件.

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.

但是，我想知道在X时刻之后是否可以检测到某个事件的缺失.例如，如果事件 A 在10秒内没有跟随另一个事件 A ，则发出警报或执行某些操作.

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.

是否可以定义一个FlinkCEP模式来捕获这种情况?

Could be possible to define a FlinkCEP pattern to capture that situation?

预先感谢，温贝托

推荐答案

尽管Flink CEP在模式末尾不支持notFollowedBy，但是有一种方法可以利用超时功能来实现.

Although Flink CEP does not support notFollowedBy at the end of a Pattern, there is a way to implement this by exploiting the timeout feature.

Flink培训包括锻炼，其中目标是通过两个小时内的START事件(而不是END事件)来识别出租车.您将找到使用CEP的此练习的解决方案

The Flink training includes an exercise 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 here.

主要思想是在10秒内定义A的模式，然后定义A，然后捕获超时情况.

The main idea would be to define a Pattern of A followed by A within 10 seconds, and then capture the case where this times out.

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