Regarding rsyslog deployment and configuration of log forwarding, you’re first going to need to determine which logs you wish to have forwarded to your rsyslog server.
Regarding the Juju logs link you provided, that configuration is for enabling log-forwarding of the juju controller and juju agent logs from either the controller or from the openstack model units, but I cannot speak to whether it would configure the deployed machines’ rsyslog agents to also forward system and application logs to your remote syslog server. My impression is that the juju configs are only for the juju logs shown with
juju debug-log which should include the logs in /var/log/juju/*.log.
If you also intend to forward all system and application logs from your openstack environment to a remote syslog server, there is a charm https://jaas.ai/rsyslog-forwarder-ha which can be related to each principle application on the servers in your model (for instance, nova-compute, neutron-gateway, mysql, rabbitmq-server, keystone, cinder, neutron-api, nova-cloud-controller, etc) and can forward ALL rsyslog logs to a central collector. You can either configure this subordinate application with the IP address of a remote syslog collector you’ve already set up in your environment external to the juju deployment, or you can follow the advice in that charm’s documentation to set up an rsyslog collector within your juju model with the rsyslog charm.
In either case, the juju controller/agent log forwarding will have to be configured separately (via the documentation you linked to) from the system and application syslog which should be configured with the rsyslog-forwarder-ha charm.
If you require further assistance, please provide details regarding which logs you wish to collect centrally and whether you’re running an extrnal rsyslog collector or if you’d like to deploy the rsyslog collector within your juju environment.