wso2 - How do I implement a continuous time window in CEP? -

say have stream of events , want able count how many of them there in time window. receive notification whenever event enters time window , changes count , same when event exits time window.

the below illustration show mean. i'm using time window of length 4 , want 3 notifications, 1 when first event enters window, second when second event enters , third when first event exits time window.

how make query that? if want group event's property?

here's have far, doesn't give me notification when event leaves window: @config(async = 'true') define stream mystream (symbol string, timestamp long) @info(name = 'query1') mystream#window.externaltime(timestamp,10 sec) select symbol, timestamp, count(timestamp) eventcount group symbol insert outputstream. siddhi cep, imagine esper similar.

from type of window in wso2 cep, can expect 2 types of events.

1. current events - these triggered when new event enters window. i.e. new event used trigger
2. expired events - these triggered when existing event in window exits it. i.e. in case of time window of 1 minute, each event kept 1 minute , emitted @ end of 1 minute

you can use combination of these 2 in same query trigger both types of events.

an example query uses both types of triggers in cep 3.1.0 (check docs here):

from stockexchangestream[symbol == 'wso2']#window.time( 1 minute )  select max(price) maxprice, avg(price) avgprice, min(price) minprice insert wso2stockquote all-events   

if want triggered using expired events, use 'expired-events' in place of 'all-events'. same applies current-events. if don't specify anything, defaults current-events, that's why current query doesn't triggered expired events.

note cep 4.0.0 syntax bit different, correct syntax check test source codes here (since docs still work-in-progress).