as far as I saw from the documentation, you can even run your existing node.js app as a separate thread. And there is no lock etc. thing since there is no context sharing.. I would prefer multiple threads and instances of my solution + multiple processes. instead single process + single thread. In other words, how about clustering both internally and externally ?
@egecan: on current node.js design you can't run the 'node.js' code in a separate context! although there are solutions, they are limited to compiling JS on v8 (webworker).. Since the design is not supporting that (lots of static variables in original code! and much more..) you can't do it by developing addin etc..
Simply, implementing multithread capabilities 'properly' into node is a big structural change and requires a fork.