What is systemd equivalent of upstart "on stopping" and "on started"

Question

I am translating my upstart scripts to systemd scripts and I am wondring what is the best practice of transalting the following:

start on started postgresql
stop on stopping postgresql

Is the Requires= section is the right for me or there is a better section?

Answer 1

start on and start on started according to upstart:

6.33 start on
This stanza defines the set of Events that will cause the Job to be automatically started.
...
6.33.2 Start depends on another service
start on started other-service

So in your case, start on started postgresql means it needs to start after postgresql has successfully started because it depends on it.

In systemd that would be:

[Unit]
Requires=postgresql
After=postgresql

Because according to the systemd.unit man page:

After=,Before= ... If a unit foo.service contains a setting Before=bar.service and both units are being started, bar.service's start-up is delayed until foo.service is started up. [...] After= is the inverse of Before=, i.e. while After= ensures that the configured unit is started after the listed unit finished starting up, Before= ensures the opposite, that the configured unit is fully started up before the listed unit is started.
...
Requires= Configures requirement dependencies on other units. If this unit gets activated, the units listed here will be activated as well. If one of the other units fails to activate, and an ordering dependency After= on the failing unit is set, this unit will not be started. [...] If a unit foo.service requires a unit bar.service as configured with Requires= and no ordering is configured with After= or Before=, then both units will be started simultaneously and without any delay between them if foo.service is activated.

---

As for stop on and stop on stopped according to upstart:

6.34 stop on
This stanza defines the set of Events that will cause the Job to be automatically stopped if it is already running.
...
6.34.3 Stop after dependent service
stop on stopped other-service

The After=postgresql mentioned above has you covered because again, according to the systemd.unit man page:

After=,Before= [...] Note that when two units with an ordering dependency between them are shut down, the inverse of the start-up order is applied. i.e. if a unit is configured with After= on another unit, the former is stopped before the latter if both are shut down.