Comment by toast0

> So you need to hot patch the running binaries. I don't really remember why it's not done in practice even though it's technically possible, I seem to remember the conclusion was that clustering (in whatever form) was the solution for high availability, rather than trying to keep a single machine running.

Most systems are technically capable of hot patching (if your exe file is mmaped, and you change the backing file, Bob's your uncle, unless your OS is no fun; which is why unix install pattern is unlink and replace rather than in-place updares). But most executables are not built to be hot patched, especially not without coordination.

Hot patching lets you make changes to your live environment with tremendous speed, but it also has risk of changing your live environment to an offline environment with tremendous speed. I'm a proponent of hot patching, and would love to be able to hot load all the things, but it has requirements and tradeoffs and most software isn't built for it, and that's probably the right decision for most things.