An example Kapacitor alert

cassandra.tick

stream
  // The following stream alerts based on changes in cpu/usage
  // Every minute the rate of change for the cpu/usage is calculated
  // Alerts are sent out when that rate is unusually high
  |from()
      .measurement('cpu/usage')
      .where(lambda: "type" == 'node' AND "nodename" =~/.*cassandra.*/)
      .groupBy('nodename')
  |derivative('value')
      .unit(60s)
      .nonNegative()
  |window()
      .period(1m)
      .every(1m)
  |alert()
      .id('{{ .Name }}/{{ index .Tags "nodename" }}')
      .message('{{ .ID }} is increasing at a {{ .Level }} rate. value:{{ index .Fields "value" }}')
      // Sigma is a built in Kapacitor function used to calculate standard deviations
      // 2 standard deviations away is about 95% greater than normal 
      .warn(lambda: sigma("value")> 2)
      .crit(lambda: sigma("value")> 2.5)

      .slack()
      .channel('#alerts')