[bnferguson]

Unsure how it is these days, but sometime back there were pretty huge issues with the rolling restart function (cluster mode pretty much didn't work, and would cause downtime) and UNIX socket handling in Puma (would hold onto sockets, would have to login to servers to clear the issue). This caused a decent bit of downtime on occasions.

I would expect these to be fixed by now, and for certain setups it simply wouldn't be an issue, but definitely put a bit caveat in "Use Puma!"

Performance wise we saw it actually be worse than Unicorn at my former company. There were a few issues but the biggest one was no out of band GC at the time, so GC time was part of the requests and something a user saw. There were some use cases where it should have destroyed Unicorn but still strangely lagged (threaded, high IO operations. Should have been able to do far more with less since Puma continues to serve while Unicorn workers will wait). Memory usage did seem better.

We ended up back on Unicorn after a few weeks of fighting. I would imagine it to be better now (no longer deal with servers at all, so no idea), but I found the dissonance between everyone heaping love on Puma at the time and the actual experience jarring.

It seemed like a fantastic project, but at the time only for certain projects and certain infrastructure setups while Unicorn was fairly bulletproof.

Of course all of this is old knowledge and with the people who are involved in the project I expect things are far better these days. Caveat lector and such. :D