This is, in my eyes, really part of a larger trend. Python for example has WSGI (which I think kicked things off), and I believe Perl has PSGI/Plack. http://ws

This is, in my eyes, really part of a larger trend. Python for example has WSGI (which I think kicked things off), and I believe Perl has PSGI/Plack. http://wsgi.org/wsgi/ http://wsgi.org/wsgi/ http://plackperl.org/ http://plackperl.org/ The commonalities seem to be (1) a library-agnostic specification, (2) a simple dictionary-based data structures, (3) pluggable and self-contained "middleware", and (4) massive adoption as people run away from the exploding burning horror of the ever-multiplying HTTP servers being written nowadays. Even large frameworks that existed before these specs get grandfathered in, like the effort to put Django on WSGI or Ruby on Rails on Rack.