Socket activation on macOS

[andre4ik3]

Issue Details

Caddy got support for socket activation on Linux in #6573 (issue #6296). Would it also be possible to add support for socket activation on macOS?

This would require calling the C function launch_activate_socket with the name parameter set to the name of the socket entry in the daemon plist file. In return it would give a list of file descriptors, which it should be possible to use with the existing support for socket activation?

It would also be nice to support EnableTransactions by calling xpc_transaction_begin when a HTTP request starts and xpc_transaction_end when it finishes. That way launchd is aware of when the service is idle or not, and can safely terminate it when it's idle for a long time to not waste resources.

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[francislavoie]

PRs welcome!

Looks like we'd need to pull in https://github.com/bored-engineer/go-launchd as a dependency to access that functionality, it should be behind an OS build flag //go:build darwin so this implementation isn't included in other OSes

[MayCXC]

#6573 implemented socket activation for all platforms with no linux dependency. you could use go-launchd or launch.h to write a utility that calls launch_activate_socket and outputs the fds, then pass them to caddy in the environment with a shell script. we could upstream this for darwin platforms with a placeholder like bind fd/{xpc.launch.name} similar to #7342.

you could also make a custom network plugin that lets you bind xpc/name or bind xpcgram/name and delimit transactions in its listeners. this seems like the better option to me because the socket activation implementation for launchd is less portable than the one for systemd.