Full disclosure...I have a hand in JRuby.

On Wed, Oct 24, 2012 at 3:15 PM, Will Bracken <lists / ruby-forum.com> wrote:
> Then I start to wonder why we're NOT using JRuby?! Instinctively, I'm
> thinking Java and Ruby is what we're doing. JRuby is the best of both
> worlds. What am I missing?

That's my question too...because I want to fill in any information
gaps that keep people from choosing to use JRuby :)

> I've asked around a little bit and I've heard a few negative things
> about JRuby, such as memory issues

JRuby does use more memory than MRI for small applications. For any
large applications, however, it can often use far less memory than
MRI. And you can do everything out of one process, where with MRI you
might need several...so there's savings that way too.

> or diminishing oracle/community
> support

I have been skeptical of the Oracle takeover of Java too...but nothing
so far has warranted my fears. They continue to run the project in the
open, progressively opening more up in the process, and their
priorities for Java and the JVM seem in line with what people want
(including language devs like me). I'm not worried about the future of
the JVM or the community that surrounds it (for now).

> Is JRuby a dud?

I don't think so, but I'm biased :)

> Or is it viable for real-world,
> large-scale, mission critical apps

There are several companies running JRuby for core parts of their
operations. Some companies run everything on JRuby. Others would not
have a product without JRuby. It's viable.

> the way Ruby/Rails supposedly is?

We'll never be perfect, but where we lag behind some aspects of MRI,
we exceed it in others. If "Ruby" and "Rails" can be viable for
mission-critical apps, then JRuby certainly is as well...and if
anything stands in the way of that I want to know about it :)

> Is
> there a reason that we should be coding in Ruby AND Java instead of just
> going with JRuby?

If a large part of your existing system revolves around irreplaceable
C extensions, or you simple need to use MRI for some other reason,
then using RJB (Ruby-Java Bridge) to call a little bit of Java would
be better. JRuby is designed to mostly drop in, but it's not a trivial
move either. We recommend people choose JRuby who really need
JRuby...if that's you, we'll work very hard to make sure your
experience goes well.

> Can we not use Rails if we do JRuby?

Rails runs just fine, and has become better acquainted with JRuby over
the years.

> I mean, why
> wouldn't you want access to all the comprehensive features in Java,
> combined with the ease/fun of Ruby?!

Indeed! And that's exactly what JRuby intends to be...a drop-in
replacement for regular Ruby for all apps that make sense, but also a
first-class citizen of the JVM with all rights therein. I think we're
doing a pretty good job of delivering that.

- Charlie