[rules-users] Group-by rule without using a fact for grouping purposes

[Wolfgang Laun]

Why is it "not practical" to add a fact for a device? You don't have
to do this up front; they may come and go, dynamically.

-W


On 05/12/2013, IK81 <ml at kofler.me> wrote:
> Hi,
>
> I am trying to figure out a rule for matching an incoming sequence of
> events, but so far I was not really successful. Basically, I want to
> process events from devices. Every event has a timestamp (long), an id
> (a UUID string), a deviceId and an error code (both are strings).
>
> What I want to have is a simple rule that fires, if a single device
> reports a certain error code (e.g. ABCD) 3 times within 5 minutes (i.e.,
> getting 3 such events within 5 minutes). So far, I suceeded in counting
> the ABCD error codes in the time window as follows:
>
>
> rule "Detect 3 occurrences of code ABCD for a certain device"
> when
>      Number( intValue == 3 ) from accumulate(
>          Event( $i : id, code == "ABCD") over window:time( 5m ),
>          count( $i ) )
> then
> 	System.out.println("Raise alarm");
> end
>
> This first attempt does not distinguish which device sent the error
> code. But how can I express to fire only if the events share the same
> deviceId? I found many solutions that use a fact (e.g., a device fact)
> to group by the device and do the accumulation. I successfully
> implemented the group-by using the following when-part of the rule.
>
> when
>      Device($deviceId : id)
>      Number( intValue == 2 ) from accumulate(
>          Event( $i : id, deviceId == $deviceId, code == "ABCD") over
> window:time( 5m ),
>          count( $i ) )
> then
>
> Adding a device fact is however not practical in my case. Are there any
> alternatives for expressing this group-by?
>
> Thanks,
> Ingo
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