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This sample demonstrates how to set up an execution plan with a pattern matching siddhi query to detect non-occurrences. In this sample we use patterns to detect non-delivered packages of a courier service within a predefined time period (for demonstration purposes we assume the time limit to deliver a package is 2 minutes here).
The query queries used in this sample is as follows. It checks whether there is a withdrawal of more than 10000, in a day where the rest of the withdrawal amounts are less than 100.
The first query keeps each arrival event for 2 minutes and then emits it to overdue_deliveries_stream which is then used in the second query.
The second query uses a pattern. It looks for a pattern where, there an arrival event (through the arrivals_stream) which is followed by a delivery event (through deliveries_stream) or else an overdue delivery event (this is an arrival event which is 2 minutes old, coming through the overdue_deliveries_stream)
Now, if the pattern detects an arrival event followed by an overdue delivery event with no delivery event, that means the package is not delivered within the 2 minute time limit.
To detect whether the delivery event is null, we use the third query isNull(deliveryId) where the deliveryId will be null if the delivery event is null.
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from arrivals_stream#window.time(2 minutes)
select *
insert expired events into overdue_deliveries_stream;
from every arrivalEvent = arrivals_stream ->
deliveryEvent = deliveries_stream[arrivalEvent.trackingId == trackingId]
or overdue_delivery = overdue_deliveries_stream[arrivalEvent.trackingId == trackingId]
select arrivalEvent.trackingId as trackingId, arrivalEvent.customerName as customerName, arrivalEvent.telephoneNo as telephoneNo, deliveryEvent.trackingId as deliveryId
insert into filter_stream;
from filter_stream [ isNull(deliveryId)]
select trackingId, customerName, telephoneNo
insert into alert_stream; |
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Start the WSO2 CEP server with the sample configuration numbered 0105. For instructions, see Starting sample CEP configurations. This sample configuration does the following:
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- Points the default Axis2 repo to
<CEP_HOME>/sample/artifacts/0105(by default, the Axis2 repo is<CEP_HOME>/repository/deployment/server).
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