Graceful binary upgrades via SIGUSR2 (?)

[Engel]

Quick and short: I stumbled about old issues/PRs like #1814 about a “zero-downtime” binary upgrade of caddy using SIGUSR2.

I wondered if this is still a thing in caddyV2 (and couldn’t find anything in the docs about it).
caddy upgrade docs explicitly says “Upgrades do not interrupt running servers; currently”.

So… this isn’t a thing anymore? Any plans/alternatives? Or any reason why it was dropped from caddy?

PS: I tried it and unsurprisingly got caddy[498]: {"level":"info","ts":1655337535.6122766,"msg":"not implemented","signal":"SIGUSR2"} — as I got into a case of needing such a feature. (I resolved my issue with a bit of manual work though)

[francislavoie]

No, it was never implemented. It’s pretty complicated to do it just right and it hasn’t been much of a priority because we don’t really expect people to be switching binaries that often. Caddy starts up fast enough that restarting should be very very fast anyways.

@Engel

caddy upgrade docs explicitly says “Upgrades do not interrupt running servers; currently”.

That’s moreso saying that running caddy upgrade won’t restart Caddy, you need to do that yourself.