A way to specify tolerance in join for relative rules

[desa]

While working with @davidgs on creating a relative rule in Chronograf, we discovered that data was buffering up at the join node.

var db = 'iotdata'

var rp = 'autogen'

var measurement = 'influxdata_sensors'

var groupBy = []

var whereFilter = lambda: TRUE

var name = 'TemperatureChange'

var idVar = name + ':{{.Group}}'

var message = ' {{ index .Fields "value" }}'

var idTag = 'alertID'

var levelTag = 'level'

var messageField = 'message'

var durationField = 'duration'

var outputDB = 'chronograf'

var outputRP = 'autogen'

var outputMeasurement = 'alerts'

var triggerType = 'relative'

var shift = 1m

0s

var crit = 0.1

var data = stream
    |from()
        .database(db)
        .retentionPolicy(rp)
        .measurement(measurement)
        .groupBy(groupBy)
        .where(whereFilter)
    |eval(lambda: "temp_f")
        .as('value')

var past = data
    |shift(shift)

var current = data

var trigger = past
    |join(current)
        .as('past', 'current')
    |eval(lambda: float("current.value" - "past.value"))
        .keep()
        .as('value')
    |alert()
        .crit(lambda: "value" > crit)
        .stateChangesOnly()
        .message(message)
        .id(idVar)
        .idTag(idTag)
        .levelTag(levelTag)
        .messageField(messageField)
        .durationField(durationField)
        .post('http://davidgs.com:1880/sensor-reading')

trigger
    |influxDBOut()
        .create()
        .database(outputDB)
        .retentionPolicy(outputRP)
        .measurement(outputMeasurement)
        .tag('alertName', name)
        .tag('triggerType', triggerType)

trigger
    |httpOut('output')

The reason for this is that the timestamps of each of the points is ~1s, but not exactly 1s. The default tolerance for join is 0s and since each point isn't exactly 1s apart, the timestamps wont line up and data will not join.

Specifying a tolerance

...
past
    |join(current)
        .as('past', 'current')
        .tolerance(100ms)
...

allows data to be joined as expected. It would be awesome to have a way to specify tolerance via the UI.

[russorat]

closing due to inactivity