what does config.threadsafe! actually do?

Does anyone know what config.threadsafe! actually does, what effect(s) it has? I'm even sure where to go looking in the source code for effects of a config variable like that, but if someone has source to recommend, I'll give it a shot (although I sometimes have trouble comprehending AR source, I must admit).

I know it tells Rails to do concurrency request handling. Okay, so far so good. But I suspect it does other things to to them make Rails behave differently to support concurrent request handling, rather than simply remove a mutex around the event loop or whatever.

I ask this because, while I'm not actually interested in concurrent request handling (don't need it), I _do_ use threads in my Rails app for other purposes. (Dealing with long-running processes, dealing with talking to slow external web services). I'm actually surprised that nobody else seems to have a use case for this, but in my app it's pretty crucial. So I'm trying to figure out what Rails 2.2 can do for me, and how I'll have to change my Rails 2.1 code to deal with it, etc.. The changes around supporting threading more intentionally are potentially good, but the only documentation or writing I can find on it (and very little of that) assumes you are interested in concurrent request handling.

Since I'm not, I don't neccesarily want to call config.threadsafe!. But I'm wondering if there are side effects of config.threadsafe! that I might want to trigger myself, to make Rails happier about handling multiple threads (possibly with AR) even without concurrent request handling.

Anyone have any info to point me to?

There is some good information right in the rails 2.2 release notes along with links to blogs with more information. http://guides.rubyonrails.org/2_2_release_notes.html#_thread_safety

Aaron

Aaron Baldwin wrote:

There is some good information right in the rails 2.2 release notes along with links to blogs with more information. http://guides.rubyonrails.org/2_2_release_notes.html#_thread_safety

Thanks Aaron. I definitely checked that out before posting, but it (and it's links) don't have quite enough information for me. They don't really say what config.threadsafe! _does_, except for allow concurrent request handling.

Guess I'll have to dive into the source at some point.