[Scylla Node Role]: update node_exporter service name

[hopugop]

Node exporter bundled with Scylla has its name changed from node-exporter to scylla-node-exporter. Thus, all affected builds are failing to start node-exporter during deployment with the Ansible Node role as it currently handles the old name only: https://github.com/scylladb/scylla-ansible-roles/blob/75a55ddacb338e5ec17349f536812568d4f990e4/ansible-scylla-node/handlers/main.yml#L27-L32

Changed on: https://github.com/scylladb/scylla/commit/95197a09c91eb719c252abed847b8c035f5f9600

Affects: scylla-4.4.0+, scylla-enterprise-2022.1~rc0+

[fee-mendes]

Best is to start both and ignore any errors. Supporting one or another is just a way to see it being left down in the long run. E.g:

  post_tasks:
    - name: "Enable and start node exporter"
      systemd:
        name: scylla-node-exporter
        enabled: True
        state: started
      ignore_errors: true

Although IMHO, this should've been a scylla-server After dependency, just like scylla-jmx is (for consistency and our own sanity), eg:

Requires=scylla-server.service
After=scylla-server.service

@vladzcloudius WDYT? I vote for an issue on the OSS list as well. :-)

[vladzcloudius]

In 2021.1.0 it's still node-exporter and in 2022 it becomes scylla-node-exporter.

@fee-mendes installation of a node exporter is optional in scylla_setup and formally it is an independent service from scylla-server.

Best is to start both and ignore any errors

I believe there should be a better way. E.g. check which of the services is installed and start the one that is installed.