Hi Nicholas,
Thanks a lot for bringing up this discussion. If I recall it correctly,
this feature has been requested many times by the users and is among one of
the most requested features in CEP. So big +1 to this feature overall.
Regarding the API, the name `partialWithin` sounds a little weird. Is it
possible to find a name which is more intuitive? Other possible solutions:
- Reuse the existing `Pattern.within` method and change its semantic to the
maximum time interval between patterns. Currently `Pattern.within` is used
to define the maximum time interval between the first event and the last
event. However, the Pattern object represents only one node in a pattern
sequence and so it doesn't make much sense to define the maximum time
interval between the first event and the last event on the Pattern object,
e.g. we could move it to `PatternStreamBuilder`. However, if we choose
this option, we'd better consider how to keep backward compatibility.
- Introduce a series of methods when appending a new pattern to the
existing one, e.g. `Pattern.followedBy(Pattern<T, F> group, Time
timeInterval)`. As timeInterval is a property between patterns and so it
makes sense to define this property when appending a new pattern. However,
the drawback is that we need to introduce a series of methods instead of
only one method.
We need also to make the semantic clear in a few corner cases, e.g.
- What's the semantic of `A.followedBy(B).times(3).partialWithin(1 min)`?
Doesn't it mean that all three B events should occur in 1 minute or only
the first B event should occur in 1 minute?
- What's the semantic of
`A.followedBy(GroupPattern.begin("B").followedBy("C")).partialWithin(1
min)``? Doesn't it mean that B and C should occur after A in 1 minute?
Besides, this FLIP only describes how the newly introduced API will be
used, however, it lacks details about how you will implement it. It doesn't
need to be very detailed, however, you should describe the basic ideas
behind it, e.g. how will you support A.notFollowedBy(B).partialWithin(1
min)? It could make sure that you have considered it thoroughly and also
makes others confident that this feature could be implemented in a clean
way.
Regards,
Dian
On Fri, May 6, 2022 at 7:32 PM yue ma <mayuefi...@gmail.com> wrote:
> hi Nicholas,
>
> Thanks for bringing this discussion, we also think it's a useful feature.
> Some fine-grained timeout pattern matching can be implemented in CEP which
> makes Flink CEP more powerful
>
> Nicholas <programg...@163.com> 于2022年5月5日周四 14:28写道：
>
> > Hi everyone,
> >
> >
> >
> >
> > Pattern#withIn interface in CEP defines the maximum time interval in
> which
> > a matching pattern has to be completed in order to be considered valid,
> > which interval corresponds to the maximum time gap between first and the
> > last event. The interval representing the maximum time gap between events
> > is required to define in the scenario like purchasing good within a
> maximum
> > of 5 minutes after browsing.
> >
> >
> >
> >
> > I would like to start a discussion about FLIP-228[1], in which within
> > between events is proposed in Pattern to support the definition of the
> > maximum time interval in which a completed partial matching pattern is
> > considered valid, which interval represents the maximum time gap between
> > events for partial matching Pattern.
> >
> >
> >
> >
> > Hence we propose the Pattern#partialWithin interface to define the
> maximum
> > time interval in which a completed partial matching pattern is considered
> > valid. Please take a look at the FLIP page [1] to get more details. Any
> > feedback about the FLIP-228 would be appreciated!
> >
> >
> >
> >
> > [1]
> >
> https://cwiki.apache.org/confluence/display/FLINK/FLIP-228%3A+Support+Within+between+events+in+CEP+Pattern
> >
> >
> >
> >
> > Best regards,
> >
> > Nicholas Jiang
>
