Add promtail_systemd_service variable (needed to configure multiple promtail instances).

[aberes]

Introduce promtail_systemd_service variable (defaults to promtail). Replace hardcoded references to promtail systemd service with {{ promtail_systemd_service }}.
Needed to configure multiple promtail instances.

[patrickjahns]

Hello @aberes

Thanks for the contribution - could you share a bit more on the use-case of configuring more than a single promtail?

Promtail itself is quite versatile with pipelines and destinations (and routing to them) - so I am not quite sure if the role needs to support the use-case

[aberes]

Hello @patrickjahns

We use two promtail instances for our servers: one for system services and journald (it sends logs to our own loki instance) and other - for application services (it sends logs to grafana cloud for our developers).
First promtail instance runs under root privileges (due to restricted log files access). Both instances have different setup for clients: section.

Example (for system services and journald instance):

- name: Setting promtail_config_scrape_configs
  set_fact:
    promtail_config_scrape_configs: '{{ global_promtail_system_config_scrape_configs + group_promtail_system_config_scrape_configs + host_promtail_system_config_scrape_configs }}'

- name: Configuring promtail
  include_role:
    name: patrickjahns.promtail
  vars:
    promtail_config_dir: /etc/promtail-system
    promtail_system_user: root
    promtail_user_additional_groups:
    promtail_systemd_service: promtail-system
    promtail_config_server:
      disable: true
    # promtail_system_pass is defined in group_vars/all/vault
    promtail_config_clients:
      - url: 'XXX'
        basic_auth:
          username: 'promtail'
          password: '{{ promtail_system_pass }}'
        external_labels:
          host: '{{ inventory_hostname }}'

[patrickjahns]

@aberes

Thank you very much for sharing - happy to include the change with the next release