ActiveSupport::Notifications threading question

rubyonrails-talk
1

Hello all.

I am planning on using ActiveSupport::Notifications and have a question about threading. For the purposes of this question I am assuming config.threadsafe! is enabled.

Will a subscriber execute in the same thread as the code that caused it to be triggered or do they run in separate threads?

I would have thought that was easy to test. Currently everything happens on the thread triggering the event. There’s also code in rails (eg ActiveRecord’s logsubscriber) that use thread local variables in notification processing so I wouldn’t that would be changed in a hurry.

Fred

2

I have done various testing using MRI and JRuby with config.threadsafe! enabled and I THINK that it does always execute in the same thread.

However since the log files are interleaved when dealing with many

requests and logs written from the subscriber do not have access to the request object for logging with a tag using something like uuid I cannot be 100% sure which is why I was hoping someone would be able to give a definitive answer.

cheers

Jeff
3

Sorry I was talking out of my arse in the last post. Correct version:

I have done various testing using MRI and JRuby with

config.threadsafe! and it appears to work in all the tests I have thrown at it, but that gives me 99% certainty (I could have missed soemthing).

I tried tracing through the code on github but quickly got lost

which is why I asked the question here to see if someone (who does know the code) could give a definitive “Yes” or “no”

Cheers

Jeff
4 
Sorry I was talking out of my arse in the last post. Correct

version:

I have done various testing using MRI and JRuby with

config.threadsafe! and it appears to work in all the tests I have thrown at it, but that gives me 99% certainty (I could have missed soemthing).

I tried tracing through the code on github but quickly got lost

which is why I asked the question here to see if someone (who does know the code) could give a definitive “Yes” or “no”

And of course there’s the difference between something just happening to behave in a certain way with the current implementation and something which a documented part of the interface. There’s not much in the way of documentation around this stuff but given that existing rails internals assume that the delivery thread is the same as the thread processing the notification I’d say it was pretty safe to rely on.

Fred