Umbrella project only works when started via iex

Questions / Help
1

Hello!

I’ve got an umbrella project with 2 apps in it: an app with business logic and an app for db access (ecto).

In the business logic app, I specified a dependency on the db app like so: {:db, in_umbrella: true}.
The business app uses the db app to insert some data on startup.

The problem is that the database isn’t modified…

… unless I start the umbrella project via iex -S mix.

I don’t get any error messages and my code in the db app is called properly (confirmed via log messages).

So I suspect my (trivial) code is working fine and it’s some startup timing problem where the db app isn’t started before the business app.

Do I need to declare anything else to make the dependency on the :db app working properly?

P.S. I even stopped my database server (postgres) and ran the project to see if I even get some error messages – which I do not get unless I launch everything via iex.

Thanks!

2

How do you start the app when it does not work?

3

From the root of the umbrella project via mix run.

4

This is not a web app, is it? I mean, how do you know or ask the app to modify the database if it’s got no web interface?

5

mix run does usually exit quickly (after the called function has returned), try to use --no-halt option as described in mix run documentation.

This though will start your application in the background as far as I remember and kept running until you shut it down by other means.

If it is a one-shot thing, you should probably consider writing a custom mix task or an escript.

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6

@hubertlepicki:

No, there isn’t a web frontend or anything like that. I connect via pgcli (postgres client) to my database and query the server.

@NobbZ:

Thanks, --no-halt does the trick! So even though there’s still a process running, the application exits because the first called function returns?

EDIT: After some searching, I found the answer to my question. mix run starts the application in its own beam process and after the start callback of the app is finished, the process gets terminated – and everything else that got started.
Here are some references for anyone, stumbling on this: https://stackoverflow.com/questions/30687781/how-to-run-elixir-application#answer-30688873
Basic: Missing a fundamental concept with applications, appreciate help - `mix run` not waiting

Thank you for you help!

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