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Comment by joelbluminator | Hacker News Reader

"Stripe relies heavily on gems with native extensions, and as you can imagine, a multi-million line Ruby codebase over time starts to depend on Ruby-the-implementation, not just Ruby-the-language.

I get it, this is a big one. How big though? I wish as a community we had a list of important gems that have an extension, maybe with a combined effort we can port them to the JVM or whatever else so people can switch between JRuby/Truffle/MRuby with relative ease. I know about the big ones: Of course Postgres/MySql gems come with extensions and probably most Ruby web servers. But what else - what are the big ones?

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TruffleRuby supports many C extensions like DB adapters out of the box like CRuby. JRuby has Java ports for most popular gems that ship alongside them. Nokogiri is one gem that's a Rails dependency and stands out as a bit of a pain, but both JRuby and TruffleRuby put in substantial effort to support it too. All three generally work with web servers, including Puma, which ships with Rails. There are still gaps in C extensions that TruffleRuby covers and lack of Java ports for less popular but still used gems. They may have some things like gRPC C extensions that don't work and they don't want to port them either. Generally the ecosystem just works between these popular Ruby implementations.

MRuby uses MGems and is just a different ecosystem entirely. It has parallel libraries but they're not shared with the above implementations.

So why the relative lack of popularity for JRuby/Truffle? I know about startup time and a degraded dev experience (compile/restart server etc is slower). Are these the major pain points? Or is it simply that most Ruby shops have a good enough performance and they're not looking for anything else?

Very slow startup and the compatibility isn't 100%. You don't get the latest Ruby features and every once in a while, code that would work on CRuby doesn't work out of the box. It's kind of a similar situation with PyPy as far as I can tell. It's been around for a long time but not much adoption.

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