Calculating Time between two events using Siddhi - complex-event-processing

Question

I am new to CEP and Siddhi. I need to calculate time on task using 2 events.
First event will have {taskId:"100", startTime="2014-11-03T18:35:00.000Z"}
Second event will have {taskId:"100", endTime="2014-11-03T18:35:57.000Z"}
Logic should be for the same taskId do endTime - startTime, will give time on task.
I am struggling to form query that can do this.
Please advice

Answer 1

You can do something like following siddhi query
define stream sensorStream (taskId string, timestamp string);
from every e1=sensorStream -> e2=sensorStream[taskId == e1.taskId]
select e1.taskId,
time:timestampInMilliseconds(e2.timestamp, "yyyy-MM-dd HH:mm:ss")
- time:timestampInMilliseconds(e1.timestamp, "yyyy-MM-dd HH:mm:ss")
as duration
insert into outputStream;
Here i have done a pattern matching [1] to catch sequence of occurring of 2 events of same task ID, then those 2 events will be assigned to e1 and e2 respectively. Finally inside select, e2.timestamp and e1.timestamp and string values will be converted to milliseconds using time extensions timestampInMilliseconds function [2] and subtracted e1 timestamp value from e2 timestamp to get the duration
[1] https://docs.wso2.com/display/CEP420/SiddhiQL+Guide+3.1#SiddhiQLGuide3.1-Pattern
[2] https://docs.wso2.com/display/CEP420/Time+Extension#TimeExtension-TimestampInMillisecondsfunction