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Queue and ready for more multi-threaded Ruby reading? Aaron Patterson has written up how the thread safe option works in Rails and some tradeoffs involved in removing the option and making thread safety the default. It’s not as complicated as you might think!
The only rub I can see is that, as far as I can tell, he’s talking about making this the default for production mode. Making it the default for development mode isn’t tenable if you want to keep class reloading around, which almost everyone does. It’s just a hunch, but running without thread-safety in development seems weird when its the default in production. But, some teams run YARV in development and JRuby in production, so maybe I’m just making up things to worry about.