// 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()