ruby-concurrency/concurrent-ruby

Cannot use Concurrent::Cancellation

Closed this issue · 3 comments

gongfarmer commented

I can't create a Concurrent::Cancellation.
Minimal reproduction:

$ ruby -rconcurrent-ruby -e Concurrent::Cancellation.new
-e:1:in `<main>': uninitialized constant Concurrent::Cancellation (NameError)

Concurrent::Cancellation.new
          ^^^^^^^^^^^^^^
Did you mean?  Concurrent::CancelledOperationError

$ ruby -rconcurrent -e Concurrent::Cancellation.new
-e:1:in `<main>': uninitialized constant Concurrent::Cancellation (NameError)

Concurrent::Cancellation.new
          ^^^^^^^^^^^^^^
Did you mean?  Concurrent::CancelledOperationError

My project uses Concurrent::Promises.future for multi-threading, and I am trying to implement a cancellation mechanism.
All my google search results suggest creating this Cancellation instance in this way.
I feel like I must be missing something obvious.

$ ruby -rconcurrent -e 'puts Concurrent::VERSION'
1.3.4

Using ruby 3.1 on debian.

gongfarmer commented

Thank you.

I'll switch back to Threads since I need cancellation and I don't see a way to do it in non-edge concurrent-ruby.

bensheldon commented

I'll switch back to Threads since I need cancellation and I don't see a way to do it in non-edge concurrent-ruby.

How are you handling it in Threads? I'm just curious because Cancellations are not particularly useful imo.

Concurrent::Future / ScheduledTask are cancellable: https://ruby-concurrency.github.io/concurrent-ruby/master/Concurrent/Future.html

The problem usually comes down to when a task/thread/code is already running, at which point it is not stoppable without (dangerously unsafely) killing the thread. Cancellations can't fix that.