topic Splunk Alert With Cron Triggering when it shouldn't in Alerting

Splunk Alert With Cron Triggering when it shouldn't

lespinoza212 — Fri, 05 Apr 2019 13:50:22 GMT

Hello,

Recently we got Splunk upgraded to version 7.2.5.1 and one of my alerts have been triggering not following it's cron schedule expression. I wrote this cron expression for an alert which only supposed to run at 8am the first Monday of every month:

0 8 1-7 * 1

Just to break this down:

0: Minute
8: Hour
1 - 7: Day of the month
*: Month
1: Day of the week (Monday)

The alert was behaving as expected before the upgrade. It have triggered on Tuesday 04/02 at 8pm Est and on Thursday 04/04 at 8pm. What may be the issue? Any help is appreciated. Thanks for your time.

Luis Espinoza

Re: Splunk Alert With Cron Triggering when it shouldn't

renjith_nair — Fri, 05 Apr 2019 14:39:39 GMT

@lespinoza212,

It does not seem to be a splunk alert issue but crontab works that way

Below is from crontab manual

Note: The day of a command's execution can be specified by two fields - day of month, and day of week. 
If both fields are restricted (ie, aren't *), the command will be run when either field matches the current time. 
For example,
"30 4 1,15 * 5" would cause a command to be run at 4:30 am on the 1st and 15th of each month, plus every Friday.

So in your case, it runs every month from 1-7 and also on every Monday

You might need to include the logic in your search

Re: Splunk Alert With Cron Triggering when it shouldn't

lespinoza212 — Fri, 05 Apr 2019 15:43:36 GMT

Hello @renjith.nair ,
Thanks for the quick response. I've read that part of the crontab manual, but if it is as it says, it would have triggered on Wednesday (04/03) as well, which it didn't. My alert triggers if my search string results count is equal to 0.

These logs are only expected on the first monday of every month.

I remembered that when I created the alert some months ago, I took as reference this post: https://answers.splunk.com/answers/495212/cron-expression-for-first-two-mondays-of-every-mon.html

Luis

Re: Splunk Alert With Cron Triggering when it shouldn't

oztraik9 — Fri, 19 Jul 2019 22:10:31 GMT

Check you cron configuration on crontab.guru

https://crontab.guru/#0_8_1-7_*_1,Check your crontab logic on crontab.guru web page:

https://crontab.guru/#0_8_1-7_*_1

Re: Splunk Alert With Cron Triggering when it shouldn't

oztraik9 — Fri, 19 Jul 2019 22:11:26 GMT

Check your cron configuration on crontab.guru site:
https://crontab.guru/#0_8_1-7_*_1