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Comment by lfittl | Hacker News Reader

I built a very similar PaaS with mongrel2 about a year ago (though all applications were untrusted and running inside an OpenVZ container) - only to change it to be nginx/HTTP-based because of stability.

Great to see this technology is ready nowadays and can be used for production systems :)

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Mongrel2 is still beta, but with a good process supervisor, it still way more robust than a RoR setup from the early days. Once in a while, it can die, I still need to instrument a bit more to track the conditions where this is the case.

On the other hand, ZMQ for the backend is just a pure pleasure and I haven't had a single failure of my components for more than 1 million real requests involving many ZMQ backend interactions.

Interesting, my problems back then were actually ZMQ-related.

Though to be fair, we were making it a bit complicated by suspending/resuming the OpenVZ containers. From that we sometimes got dead ZMQ connections that were black holing all traffic (incredibly hard to debug - ended up switching because of it).

OpenVZ is tricky, they are patching the kernel pretty deep and this creates a lot of hard to debug issues. I had a lot of troubles with containers running software mapping big files like MongoDB.

Yes, most of my crashes on the mongrel2 server I run come from ZeroMQ too. They fix them when I find them, but I actually run my servers under valgrind continually so I can catch them and report them.

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