fireproofsocks

fireproofsocks

I’m starting to get deeper into the subtleties of supervisors and I could use some help understanding how and when to restart failed tasks.

Given I have a risky_function() that may raise errors, I can ensure that it eventually completes by supervising a task that calls it by doing something like this (assume MyTaskSupervisor is started):

Task.Supervisor.start_child(MyTaskSupervisor, fn -> 
  risky_work() end, 
  restart: :transient)

Even if the risky_work function hits errors, it restarts and it eventually completes successfully.

This is (I think) an example of a non-awaited task. How would this need to be structured if I wanted that same risky_work to be part of an awaited task?

The following attempt doesn’t ensure that the task completes:

task = Task.Supervisor.async_nolink(MyTaskSupervisor, fn ->
  risky_work()
end)
Task.await(task) # or Task.yield(task)

The risky_work function is called immediately and any errors it raises are immediately visible. The docs show how Task.Supervisor.async_nolink/3 might get used inside of a GenServer… I can get that example working, but it still doesn’t ensure that the risky_work ever completes. I can see where I can restart the task – there’s even a comment in the example # Log and possibly restart the task..., but if I am restarting the task, I feel like I’m doing something wrong. Isn’t that what the supervisor is supposed to do?

Thanks for any clarifications! I feel like maybe I’m thinking about this the wrong way. :thinking:

Showing Posts 1 to 2

al2o3cr

al2o3cr

The way that an await-able Task gets its arguments isn’t compatible with being restarted by a standard Supervisor - the Task process is started up, and then the MFA and alias to use are sent to it:

https://github.com/elixir-lang/elixir/blob/v1.17.2/lib/elixir/lib/task/supervisor.ex#L599-L603

https://github.com/elixir-lang/elixir/blob/47abe2d107e654ccede845356773bcf6e11ef7cb/lib/elixir/lib/task.ex#L512-L516

So “restarting” the task process will leave it waiting for that initial tuple message forever.

This is obliquely referenced in the documentation for Task.Supervisor.async_nolink/3:

Note this function requires the task supervisor to have :temporary as the :restart option (the default), as async_nolink/3 keeps a direct reference to the task which is lost if the task is restarted.

fireproofsocks

fireproofsocks OP

Interesting. Thanks!

— All posts loaded —

Where Next? Top

Trending in Questions Top

RSP87
I’m working on a project that simulates the bumbl example in the programming phoenix book. It acts almost like an email client. We have a...
New
kpanic
Hi everyone, I am toying with the idea of building a “match maker” for giving personal help to people that wants to start coding. I sta...
New
nseaSeb
Hello, I know there is an approach for handling lists that allows for optimized traversal, but I can’t recall the specific method (somet...
New
brecabral
Documentation While reading the Scoped Routes section, I noticed that the documentation currently refers to a problem without explainin...
New
velrest
So my question is quite simple and i have found no conclusive answer on forum, google or AI. Should we use :erlang.float for Integer to ...
New
asweet-confluent
I recently noticed that Elixir’s Logger defaults its primary log level to :debug when no :logger, :level application configuration is pre...
New
apz
I’m new to elixir and just tried to install the elixirLS extension for VScode(ium) and it is throwing some errors that I would like help ...
New

Other Trending Topics Top

GenericJam
Edit: 2026 May 15 - This post is archived. Mob is alive!! Main docs: mob v0.7.11 — Documentation A bit of explanation for the slightly c...
New
JesseHerrick
Hey, I’m Jesse and I’m the main contributor behind Dexter, a full-featured, lightning-fast Elixir LSP optimized for large codebases. It s...
New
mudasobwa
I am happy to introduce the very α version of the new programming language compiled to BEAM. Welcome Cure. It has literally three kille...
New
marciok
Hi there! We created Gust: A task orchestrator inspired by Airflow. For those who have never heard about Aiflow, it’s a Python-based wor...
New
mhanberg
Hi everyone! The first release candidate for the Expert language server project is now available! We’ve published a press release detai...
New
jimsynz
Beam Bots (or just BB for short) is a framework for building fault-tolerant robotics applications in Elixir using familiar OTP patterns. ...
New

We're in Beta

About us Mission Statement

Options

Thread Display Mode




Thread Preview

Skip Thread Previews