Dealing With Rails Single Thread Design

I hope Rails becomes mutli-threaded in a not-to-distant future
release. That would relieve much of the criticism of Rails due to its
single threadness. In reading Dave Thomas' book, Agile Web
Development with Rails, 2nd ed, section 27.2, page 617, he indicates
the way to scale Rails is to have a front end HTTP proxy server that
sends rails requests to back end rails processes. In the next
paragraph, he refers to these processes as application servers. I
understand this to mean each rails implementation runs on its own
"box." If my understanding is not correct, stop me now and set me

However, if my basic understand is basically correct, this seems like
a rather expensive approach of having to add a "box" everytime the
system slows down.

Here is my question, can the single thread issue be solved by running
multiple rails instances on a single powerful box using some level of
Virtualization? Please follow this link to Wikipedia's section on
Virtualization for more info:
If this can be done, does anyone know what level/kind of
virtualizations is required?

Any wisdom that you can provide would be much appreciated.

Thanks again!

You can run as many processes as you'd like on a single piece of physical hardware (within reason).


The idea is that you run a number of backend server processes
(something like Mongrel) that have your Rails apps running with a
"frontend" server (like Apache or Lighttpd or nginx) for static file
serving, load balancing, forwarding requests to the backend, etc. You
can run a number of backend processes on a single box, no
virtualization required. :slight_smile:


Another thing to consider is that handling concurrent requests using
multiple instances of these "backend server processes" is inherently
much safer than multi-threading inside a single instance.

Threading is a technique that is VERY difficult to get right.
Generally the benefit that you gain from multi-threading can easily be
overshadowed by the problems that it causes when not done 100%
correctly. In a single threaded application you don't have to worry
about situations like deadlocking and lock management in general.

In my opinion using a mongrel cluster is much preferred over multi-
threaded Rails. It certainly makes life much less complicated for the
average developer.