How to properly use Mariaex / DBConnection?

I have an application which I’m using Mariaex to query a MySQL db, but I’m not using Ecto. I’m curious what the proper way is to handle connection/instances of Mariaex for a long-running application? Under the hood, Mariaex uses DBConnection to create the connection and do all the connection pooling stuff, but I’m unsure if I’m supposed to just start one instance of Mariaex (via start_link) and hold on to that pid for the duration of the application (ultimately I’m sure I’d use a supervisor), or if I should be calling Mariaex.start_link/1 each time I want to perform a new query? If the latter, do I manually stop the pid returned by Mariaex.start_link/1 when the query has completed? Does DBConnection handle shutting it down?

I’ve looked through Mariaex, DBConnection, and Ecto’s codebases to try to understand how it’s handled in Ecto, but there’s a sufficient amount of abstraction and indirection that I haven’t really been able to tell how Ecto handles this.

I’d appreciate any advice anyone could provide on this.

** UPDATE **
Sorry, I guess I shouldn’t have posted this on a day when I was loaded up on cold medicine. I now see that I had forgotten to set the pool to DBConnection.Poolboy or DBConnection.Sojourn, (though in observer there was a DBConnection.Sojourn.Supervisor started, so I naively assumed sojourn was being used by default), and had confused myself about the connection behavior.


Hi there,

I seem to have the exact same issue you do. Mainly when I use the Mariaex.transaction method, the connection seems to not function properly afterwards.

I believe I haven’t confired a pooling mechanism (poolboy or Sojourn). Where and how do you do this?

It’s in the options you pass to Mariaex.start_link/1, Mariaex.query/4, and again in the options passed to Mariaex.transaction/3. See

Hope this helps!

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Thanks this is exactly what I was looking for.

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Is there any example of correct use of this library? Especially when it comes to opening and reusing conenctions (without Ecto)?

Hey, I had this blog post as draft for quite some time now, just published it for you:

is this helpful?


Absolutely, it was the very piece of code I was looking for :slight_smile: (I mean, using Supervisor and Poolboy). For my current little project, maximum 3 people would be interacting with the database at the same time, but I guess it is still better to set the connection up and let Poolboy handle the connections. Thank you.