Hello once again, If you want to use CEP library you can e.g. key by device, then apply pattern:
Pattern.<Event>begin("connect").where(...)
.followedBy("established").where(new IterativeCondition<Event>() {
@Override
public boolean filter(
Event value, Context<Event> ctx) throws Exception {
return
ctx.getEventsForPattern("connect").iterator().next().getPort().equals(value.getPort());
}
})
.within(Time.milliseconds(X));
Then you can select the timed out partial matches[1] only.
This latest feature that you need in this example is the
IterativeCondition which was introduced in flink 1.3.
If you don't like the CEP API you may want to try implement the same
logic with ProcessFunction[2] and register timers on the connect event
yourself.
Similar solutions you can find in those trainings:
http://training.data-artisans.com/exercises/rideCleansing.html and
http://training.data-artisans.com/exercises/CEP.html
Best,
Dawid
[1]
https://ci.apache.org/projects/flink/flink-docs-release-1.7/dev/libs/cep.html#handling-timed-out-partial-patterns
[2]
https://ci.apache.org/projects/flink/flink-docs-release-1.7/dev/stream/operators/process_function.html
On 13/12/2018 09:20, Spico Florin wrote:
> Hello, Dian!
>
> Thank you very much for your explanations. In my case, CEP patterns
> are based on the event time. Also, as you said I have many devices and
> also many ports on that devices. Therefore, I'm using keyed streams.
> So I would like to know which device was disconnected on which port.
> Is that feasible Flink? If yes in what version and how?
>
> Regards,
> Florin
>
>
> On Thu, Dec 13, 2018 at 4:37 AM fudian.fd <fudian...@alibaba-inc.com
> <mailto:fudian...@alibaba-inc.com>> wrote:
>
> Hi Florin,
>
> Are you using processing time or event time? The JIRA FLINK-7384
> allows to emit timed-out patterns without having to wait for the
> next element ONLY in processing time. For event time, it still
> needs the watermark to trigger the emitting of matched or
> timed-out patterns. Besides, the watermark is global for the whole
> job, not per key. In your application, SNMP will not send anymore
> data for one device when it's disconnected. But if there are many
> devices to be monitored, the watermark will still progress as long
> as there are some devices connected. If it's the case that there
> are no elements at all, the mentioned assigner will look like the
> following:
>
> class PeriodicExtractor implements AssignerWithPeriodicWatermarks<Long> {
>
> private volatile long maxTimestamp = Long.MIN_VALUE;
>
> private static final long MAX_IDLE = 5 * 60 * 1000; // 5 minutes
> private static final long OFFSET = 30 * 1000; // 30 seconds private
> volatile long lastTimeReceivedElement = 0L;
>
> @Override public long extractTimestamp(Long element, long
> previousElementTimestamp) {
> maxTimestamp = Math.max(maxTimestamp, element);
> lastTimeReceivedElement = System.currentTimeMillis();
> return element;
> }
>
> @Nullable @Override public Watermark getCurrentWatermark() {
> if (System.currentTimeMillis() - lastTimeReceivedElement >=
> MAX_IDLE) {
> maxTimestamp = Math.max(maxTimestamp, System.currentTimeMillis()
> - OFFSET);
> }
> return new Watermark(maxTimestamp);
> }
> }
>
>
> Regards,
> Dian
>
>> 在 2018年12月13日，上午12:06，Andrey Zagrebin
>> <and...@data-artisans.com <mailto:and...@data-artisans.com>> 写道：
>>
>> Hi Florin,
>>
>> I think Dawid might help you. I am pulling him into the discussion.
>>
>> Best,
>> Andrey
>>
>>> On 12 Dec 2018, at 16:24, Spico Florin <spicoflo...@gmail.com
>>> <mailto:spicoflo...@gmail.com>> wrote:
>>>
>>> Hello!
>>> I'm using the same questions as in this stackoverflow
>>> post
>>> https://stackoverflow.com/questions/50356981/apache-flink-cep-how-to-detect-if-event-did-not-occur-within-x-seconds?rq=1,
>>> due to fact that I need the same functionality.
>>>
>>> My use case is to detect when an device is disconnected from a
>>> server (for example).
>>> From SNMP I'm sending the data to Kafka then to Flink CEP and
>>> check whether I have the established connection within X seconds.
>>> If the window of X seconds timedout, then I can consider that
>>> the device is disconnected.
>>> The issue is that, when the device is disconnected, SNMP does't
>>> send anymore data about that port that was used. Thus no event
>>> is sent to CEP. Only when the device is connected again then,
>>> the disconnected event is triggered.
>>>
>>> The same functionality was requested in this post
>>> too:
>>> https://stackoverflow.com/questions/51399973/flink-time-window-based-on-event-time-output-nothing.
>>>
>>> I checked the status of the jira ticket regarding this feature:
>>>
>>> https://issues.apache.org/jira/browse/FLINK-7384
>>>
>>> but unfortunately, is still open.
>>>
>>> In the official
>>> documentation,
>>> https://ci.apache.org/projects/flink/flink-docs-stable/dev/event_time.html,
>>> in the paragraph related with Idling sources, somehow the
>>> situation described resembles what we need:
>>> "Currently, with pure event time watermarks generators,
>>> watermarks can not progress if there are no elements to be
>>> processed. That means in case of gap in the
>>> incoming data, event time will not progress and for example the
>>> window operator will not be triggered and thus existing windows
>>> will not be able to produce any output data.
>>> To circumvent this one can use periodic watermark assigners that
>>> don’t only assign based on element timestamps. An example
>>> solution could be
>>> an assigner that switches to using current processing time as
>>> the time basis after not observing new events for a while."
>>>
>>> Unfortunately, no example of how the mentioned assigner looks
>>> like. A full example will help us to check whether the mentioned
>>> solution works or not.
>>>
>>> Therefore, can you please share your thoughts about this feature?
>>> Is feasible? If yes,please provide the Flink version that solve
>>> it and the example.
>>> Is still a limitation and there is no plan to solve it in near
>>> future?
>>>
>>> I look forward for your answers.
>>>
>>> Best regards,
>>> Florin
>>>
>>>
>>
>
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