relative-stream-template.tick

var db string  // database per service function chain, so db is named after sfc

var rp = 'autogen'  // default value for the retention policy

var measurement string

var selectLambda lambda  // must be a lambda specifying the field to select e.g. "requests"

var whereClause = lambda: True  // default value is a function which returns TRUE, hence no filtering of the query result

var messageValue = 'TRUE'  // default value is TRUE, as this is what SFEMC expects as a notification for an event rule

var comparisonLambda lambda  // comparison function e.g. "diff" > 40

var alertPeriod duration

var topicID string


var data = stream
    | from()
        .database(db)
        .retentionPolicy(rp)
        .measurement(measurement)
        .where(whereClause)
    | eval(selectLambda)
        .as('value')

var past = data
   | shift(alertPeriod)

var current = data

past
    | join(current)  // NOTE: join buffers a given data point until a point with the correct timestamp to join on arrives
        .as('past', 'current')
    | eval(lambda: float("current.value" - "past.value"))
        .keep()
        .as('diff')
    | alert()
        .id(topicID)
        .details('db=' + db + ',measurement=' + measurement)
        .crit(comparisonLambda)
        .message(messageValue)
        .topic(topicID)
        .noRecoveries()