Time Gap Alerting

Technical Complexity

Medium

Source code for example this is here.

Purpose

Monitor a inbound event stream. If a time gap occurs (no event for a maximum amount of time) We generate an event.

Situation

Taking in feed of security cameras
Receiving heart beat of servers (If one goes down or is overloaded, the event will arrive late, or never)
Receiving input of monitored equipment

Design

This is based on the precept of a sliding window. When the window goes below a threshold of events, an alert is generated.

casa.PNG

IEP Constructs Used

Process Flow

iepProcess.PNG

Inbound stream
Partitioned Window
Relational Updates

WSDL Modifications

You will need to change the output of the stream that is currently mapped on the file system to a soap output. This will allow you to drop the wsdl and use the output directly as an input in the BPEL process. Keep a backup copy!! As iep will ease your modifications each time the iep process is regenerated.

Partitioned Window

partitionedWindow.PNG

We can see in this operator that we've set to keep the last 3 elements of the stream, for each stock. So this way, we have a shallow history on each element important for us.

BPEL Process

All this does, is check the tag. If the tag=+, then we do an insert. if the tag=-, then we do a delete. The ems seq id is used to manage the correlation in the two events (+ and -). The setDBValues does the map of the data between the iep process stream and the external DB representation.

bpelProcess.PNG