Stop processing expressions in tickscript

1

I’m writing a device’s SMART alert. Telegraf plugin gather data, but if device is heavily damaged, it may cause plugin not to gather all needed values (fields).

I have a set of expressions to check all those conditions (unable to gather smart, smart is not enabled, check if metrics are ok).

Every time I have a mangled data (due to failing disks) I have ‘very bad’ alert (as planned), but this cause other expressions to write an error into kapacitor log because there is no fields to process.

My code in question:

var raw_data = stream
    |from()
        .measurement('smart_device' )

var rw_errors = raw_data|from()
  .where(lambda: "read_error_rate" != 0 OR "write_error_rate" !=0)

var smart_enabled = raw_data|from()
  .where(lambda: "enabled" != 'Enabled')

var health_not_ok = raw_data|from()
  .where(lambda: "health_ok" == FALSE)

var exit_status = raw_data|from()
        .where(lambda: "exit_status" != 0)

rw_errors|alert()
  .crit(lambda: "read_error_rate" > 0)
  .id('read_error_rate')
  .message('Read error rate for for /dev/{{ index .Tags "device" }} at {{ index .Tags "host" }} is non-zero ({{ index .Fields "read_error_rate" }})')
  .topic('<< kapacitor_device_smart_topic >>')
rw_errors|alert()
  .crit(lambda: "write_error_rate" > 0)
  .id('write_error_rate')
  .topic('<< kapacitor_device_smart_topic >>')
  .message('Write error rate for for /dev/{{ index .Tags "device" }} at {{ index .Tags "host" }} is non-zero ({{ index .Fields "write_error_rate" }})')
health_not_ok|alert()
  .crit(lambda: "health_ok" != FALSE)
  .id('drive_health_status')
  .message('/dev/{{ index .Tags "device" }} at {{ index .Tags "host" }} is failing!')
  .topic('<< kapacitor_device_smart_topic >>')
exit_status|alert()
  .crit(lambda: "exit_status" != 0)
  .id('smartctl_exit_status')
  .message('Smartctl return non-zero exit code ({{index .Fields "exit_status"}}) for /dev/{{ index .Tags "device" }} at {{ index .Tags "host" }}')
  .topic('<< kapacitor_device_smart_topic >>')
smart_enabled|alert()
  .crit(lambda: "enabled" != 'Enabled')
  .id('no_smart_for_device')
  .message('Unable gather SMART for /dev/{{ index .Tags "device" }} at {{ index .Tags "host" }}')
  .topic('<< kapacitor_device_smart_topic >>')

If record have no read_error_rate, there is an kapacitor error:

ts=2018-08-14T14:14:20.716Z lvl=error msg="failed to evaluate WHERE expression" service=kapacitor task_master=main task=device_smart node=alert6 err="left reference value \"read_error_rate\" is missing value"

Is any way to say kapacitor ‘stop processing other expressions’? Like ‘return’, or ‘stop’, or something like that…

Or, in another way: is there a way to check if some field is present or not?

Thanks!

2

hi,

you can check if a point is present at the time using isPresent, i couldn’t link directly to the section in the page
isPresent

It will return a boolean value depending if the data point exists and will supress the errors you get when the data point doesn’t exist.

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