Auto delete post at some time

Phoenix Forum Questions / Help
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1

Hello
I am working on Phoenix app and I am beginner with Elixir in general. I have a question regarding one scenario that I need to implement.

Lets say, User creates Post. That post has expire_time property, and it is exactly what you think it means. Phoenix should auto delete that Post when I reach that time. For example, auto delete in 60 seconds.

I am aware that there can be some cron job be in charge for that, but I want also to ask, maybe some Plug is already written for this kind of job. Can someone give me some tips?

Thank you

2

Hello,

Phoenix will not help you for that. Plug only deals with HTTP requests.

If you do not want to use CRON you can start a GenServer as part of your application supervision tree that checks for post to delete every N seconds, that would be simple.

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3

I see. Thank you for helping, I will look into GenServer for that.

4

You can call :timer.send_interval(30_000, :delete_posts) in the init/1 callback.
And then

def handle_info(:delete_posts, state) do
   delete_expired_posts()
  {:noreply, state}
end

Edit: Now if you do not know anything about GenServer I must warn you that there are several concepts to understand (although in the end it is quite simple). A CRON will work well, and you can also look at Quantum though it is overkill if you only need one kind of periodic job.

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5

Yes, I think GenServer is a way to go with this. I dont need any overkill solution for now. Project is simple in nature and I want to keep it like that.

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6

You could also reach for Oban — Reliable and Observable Job Processing. It depends on a Postgres database and you can specify Jobs wirth a scheduled_at or scheduled_in argument.

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7

A possibly simpler approach, depending on how your app works, could be to delete the expired post when it is accessed.

Or even easier, just exclude expired posts when accessing them, leaving them in the database.

3 Likes
8

From an efficiency perspective, a periodic job that deletes expired records en mass should be easier on the database. Also soft delete is setting yourself for trouble later on, IMHO.

9

GenServer would be the best option, hopefully you’d have already found a solution… :sweat_smile: