Supporting socket activation would make each of the following possible for admins:
- Cleaner restarts (the listener socket stays open persistently)
- Network namespace isolation, disallowing any network access beyond the inherited listener port (and connections accepted from it).
- Lazy startup for densely hosted instances. (It's also possible with socket activation to start it eagerly, as usual.)
- Running MariaDB on privileged ports without having to start it initially as root
- Non-racy startup for services (like a PHP site) that depend on connecting to MariaDB. Because systemd opens listener sockets early in boot, they're available even while MariaDB is starting
- Deeper integration into coming network support in future systemd releases
Some examples in C are here:
I am willing to sponsor development of this feature.