This has considerable merit.
One thing that is unfortunate about cron is that it provides little
verifyable feedback. It logs some things, sort of...
A "cron implementation using PostgreSQL as data store" would have a
wonderfully natural place to record log information in a usefully
structured fashion.
When a job runs, it would be a splendid idea to record such things as:
- Job ID (perhaps an OID, or some other candidate primary key)
- PID
- Start time
- End time
- Exit code
Given all of the above, a job might look at the logs and
self-terminate if there's another instance still running from last
hour.
Jobs that are supposed to be mutually exclusive could detect as much.
You could _attempt_ to run a job every hour, and have it decide "Oh,
I've already run successfully in the last [interval], so I'll not
bother."
None of this means forcing it into the database implementation; it
just means that it would be useful. "pgcron" sounds like an utterly
splendid idea.
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