ScheduledRecordDeletion FirstTimeRun Notation

[erikjanwestendorp]

What type of issue is it? (Choose one - delete the others)

Wrong documentation?

What article/section is this about?

ScheduledRecordDeletion

Describe the issue

It mentions a “first time run” with the cron expression * 4 * * *. I’m not sure about the exact implementation in Umbraco Forms, but this seems a bit confusing. The article states that the first run will be at 4 a.m., but as far as I know, * 4 * * * means every minute during the fourth hour (04:00–04:59).

So if my Umbraco instance restarts at 4:05 a.m., the first run would actually happen at the next minute (04:06), not at 4 a.m. the following day, right?

[eshanrnh]

Hey @erikjanwestendorp 👋

Sorry for the delay. I reached out to the team, and they mentioned, that this is parsed using the ICronTabParser from the CMS, which relies on NCrontab.

According to NCrontab's documentation, this expression runs every day at 04:00, not every 4 minutes.

Hope this helps 🤞

[erikjanwestendorp]

Hi @eshanrnh thanks for your reply. I did notice that NCrontab is being used. I understand that it doesn’t run every minute, my question is more about when the task runs for the first time.

I believe the GetNextOccurrence method is used to determine that.

Cron expression	App start time	GetNextOccurrence(DateTime.Now) returns
0 4 * * *	10:00	tomorrow at 04:00
0 4 * * *	04:00	tomorrow at 04:00 (today’s 04:00 is already passed)
* 4 * * *	10:00	tomorrow at 04:00
* 4 * * *	04:30	today at 04:31

[ronaldbarendse]

@erikjanwestendorp Forms uses the same configuration format for the ScheduledRecordDeletion as Health Checks in the CMS (FirstRunTime as cron expression and Period as timespan), which uses the shared RecurringHostedServiceBase class that indeed uses GetNextOccurrence() to determine the initial delay after startup.

However, the FirstRunTime configuration value is empty by default, so it runs after the 3 minute delay when enabled (and repeated after a default 24 hour delay).

As you correctly highlighted, using * 4 * * * will result in potentially running the task within 1 minute of startup and potentially multiple times if the application restarts between 04:00 and 04:59.

Considering this and looking at the documentation, I agree we should change this to 0 4 * * * and make the default values/behavior a bit more clear for both CMS and Forms!

[erikjanwestendorp]

@ronaldbarendse Thanks for the explanation, just created a PR! :-)