Debugging processes in LiveBook

Elixir Framework Forums Livebook Forum
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I’m trying to test out some supervision stuff with GenServers in LiveBook. I’ve easily managed to start the GenServers, which I assume are running under some master LiveBook supervisor.

My question is; how do you debug a process running in the background in LiveBook? As far as I can tell, there’s no way to access the console in LiveBook. So how can I debug this without console access?

I need to send it messages and normally I’d just have it print out some results to the console when it get the message and processes it.

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You could probably start observer to see if your theory about the supervision tree is true.

You can start an iex shell iex --sname coolname --cookie monster -S mix and then attach your livebook session to that.

And, can’t you just send messages to your GenServer from livebook anyway? Throw some inspect/puts/Logger.debug and you should see that in livebook.

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I don’t really want to rely on being able to SSH in to open a new IEx session on the server running LiveBook, as the whole point of LiveBook is to run in the browser.

Maybe I could just have the process I’m testing send messages to the LiveBook process and then I could just receive them and read them. I’ll try that

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Sorry, I don’t really understand what you’re doing. I assumed you were doing all this locally to learn about processes and supervision.

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I’m just trying to use LiveBook to play around with things that require processes and supervision. But I can’t view the console when in LiveBook so it’s hard to debug those processes as there’s no way to just IO.inspect from a process in LiveBook to have it print out somewhere (as far as I can see).

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Have you tried doing a Logger.info call from a process? I think that should get printed out by Livebook (at least it does in NervesLivebook and I don’t think it is setting up anything special there).

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Wow that’s awesome! Thanks for the tip! I never would have thought to use Logger! It’s a bit odd that it runs in whatever cell was evaluated last but it works!

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