Exec event handler

The exec event handler executes an external program. Event data is passed over STDIN to the process.

Options

The following exec event handler options can be set in a handler file or when using .exec() in a TICKscript.

Example: handler file

id: handler-id
topic: topic-name
kind: exec
options:
  prog: /path/to/executable
  args: 
    - 'executable arguments'

Example: TICKscript

|alert()
  // ...
  .exec('/path/to/executable', 'executable arguments')

Using the exec event handler

The exec event handler can be used in both TICKscripts and handler files to execute an external program based off of alert logic.

Note: Exec programs are run as the kapacitor user which typically only has access to the default system $PATH. If using an executable not in the $PATH, pass the executable’s absolute path.

Execute an external program from a TICKscript

The following TICKscript executes the sound-the-alarm.py Python script whenever idle CPU usage drops below 10% using the .exec() event handler.

exec-cpu-alert.tick

stream
  |from()
    .measurement('cpu')
  |alert()
    .crit(lambda: "usage_idle" < 10)
    .exec('/usr/bin/python', 'sound-the-alarm.py')

Execute an external program from a defined handler

The following setup sends an alert to the cpu topic with the message, “Hey, check your CPU”. An exec handler is added that subscribes to the cpu topic and executes the sound-the-alarm.py Python script whenever an alert message is published.

Create a TICKscript that publishes alert messages to a topic. The TICKscript below sends an alert message to the cpu topic any time idle CPU usage drops below 10%.

cpu_alert.tick

stream
  |from()
    .measurement('cpu')
  |alert()
    .crit(lambda: "usage_idle" < 10)
    .message('Hey, check your CPU')
    .topic('cpu')

Add and enable the TICKscript:

kapacitor define cpu_alert -tick cpu_alert.tick
kapacitor enable cpu_alert

Create a handler file that subscribes to the cpu topic and uses the exec event handler to execute the sound-the-alarm.py Python script.

exec_cpu_handler.yaml

id: exec-cpu-alert
topic: cpu
kind: exec
options:
  prog: '/usr/bin/python'
  args: 
    - 'sound-the-alarm.py'

Add the handler:

kapacitor define-topic-handler exec_cpu_handler.yaml