Replace delay with scheduled_for?

[kirillsalykin]

https://github.com/maxcountryman/underway/blob/main/migrations/20240921151751_0.sql#L50

Currently the delayed tasks are implemented via delay field.

Wdyt about adjusting this slightly, so it rely on scheduler_for.

so instead of and created_at + delay <= now(), it will check scheduled_for <= now()?

The only reason it feels a bit "cleaner" for schedule for a specific time (and makes query a little simpler).

it is very subjective, thus currious about your opinion on this?

(of course it can also be solved with a fn that makes delay out of schedule_for), but this way (`schedule_for) "feels" cleaner for me for both schedule and dequeue)

[maxcountryman]

One of the reasons for using intervals is to ensure that all the time zone conversions happen in Postgres. Notice how we always use Postgres to create timestamps and only use spans that are converted to intervals as application-level parameters.

I think it would also be a little misleading to say it's scheduled for a particular wall clock instant because in reality it's not (the scheduler is required for that). Instead it's actually a duration before which the task can't be dequeued and after which it may or may not be.

So I generally think interval delays are a slightly more appropriate interface.

[kirillsalykin]

tbh, there is no strong reason, it just feels more natural.
but probably you are right, it is not worth the trouble, scheduled_at can be implemented in terms of created_at + delay

[maxcountryman]

it is not worth the trouble

I'm particularly concerned about time zones here because Postgres is already going to be converting from stored UTC to whatever the cluster is configured with. Rather than try to account for that in the application, I'd prefer to just let Postgres handle all conversions to the extent possible.

[kirillsalykin]

AFAIK, psql stores everything in UTC.

[kirillsalykin]

anyway, i dont think it worth it. lets use delay.

[maxcountryman]

Yes it does, but once read it's converted to the locale the cluster is to set (that could be UTC or anything else).