Add HoltWinters method

[nathanielc]

Add Holt Winters InfluxQL function

For example one can now define an alert based off forecasted future values.

The following TICKscript will take the last 30 days of disk usage stats and using holt-winters forecast the next 7 days. If the forecasted value crosses a threshold an alert is triggered.

The result is now Kapacitor will alert you 7 days in advance of a disk filling up. This assumes a slow growth but by changing the vars in the script you could check for shorter growth intervals.

// The interval on which to aggregate the disk usage
var agg_interval = 1d
// The number of `agg_interval`s to forecast into the future
var forecast_count = 7
// The amount of historical data to use for the fit
var history = 30d

// The critical threshold on used_percent
var threshold = 90.0

batch
    |query('''
    SELECT max(used_percent) as used_percent
    FROM "telegraf"."default"."disk"
''')
        .period(history)
        .every(agg_interval)
        .align()
        .groupBy(time(agg_interval), *)
    |holtWinters('used_percent', forecast_count, 0, agg_interval)
        .as('used_percent')
    |max('used_percent')
        .as('used_percent')
    |alert()
         // Trigger alert if the forecasted disk usage is greater than threshold
        .crit(lambda: "used_percent" > threshold)
        .slack()

• Rebased/mergable
• Tests pass
• CHANGELOG.md updated

[elvarb]

Is holtWinters out of the project? it does not seem to be available nor in the documentation except for version 0.10

[nathanielc]

@elvarb Its part of the 1.0 series. https://docs.influxdata.com/kapacitor/v1.0/nodes/influx_q_l_node/#holtwinters

[elvarb]

Ah, all makes sense now. Thanks 👍