do not run systemd service when another service ran sucessfully

Question

I have two services for an application:

1. healthcheck- which check the health of a system and attempts restart when the validation fails.
2. rollback- when multiple restart attempts fails to pass the healthcheck, it does the rollback to the previous version.

the unit file looks like this for health check:

[Unit]
Description=greenboot Health Checks Runner
Before=boot-complete.target
OnFailureJobMode=fail

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/libexec/greenboot/greenboot health-check
Restart=no

[Install]
RequiredBy=boot-complete.target
WantedBy=multi-user.target

and rollback

[Unit]
Description=Greenboot rollback
DefaultDependencies=no
Before=multi-user.target ostree-finalize-staged.service greenboot.service
Wants=local-fs.target
After=local-fs.target
ConditionNeedsUpdate=|/etc
ConditionNeedsUpdate=|/var

[Service]
Type=oneshot
RemainAfterExit=true
ExecStart=/usr/libexec/greenboot/greenboot rollback
Restart=no

[Install]
WantedBy=multi-user.target

rollback has other set of trigger conditions including a grub variable, How can I ensure the the health-check service does not run when rollback run with exit code 0.

Answer 1

Try to make use of the OnFailure= in health check to activate rollback when it fails, and SuccessAction=reboot in rollback to automatically reboot the system after your "rollback" operation finishes successfully.

In both units, IMHO, RemainAfterExit=true is unwanted. (Well at least in rollback)

Only health check should contain an [Install] section because the other should only be activated on failures...

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To properly answer the topic title, without regarding the use-case of the poster:

1. You should make use of ConditionPathExists=!/some/path/filename, in service "A" to prevent it being run when that file exists.
2. And create that file in the other service "B" in an ExecStartPost= directive, to prevent the first service "A" to start, when this service "B" exits successfully.