matrix-docker-ansible-deploy/roles/matrix-prometheus-node-exporter/tasks/init.yml

---

- set_fact:
    matrix_systemd_services_list: "{{ matrix_systemd_services_list + ['matrix-prometheus-node-exporter.service'] }}"
  when: matrix_prometheus_node_exporter_enabled|bool

- block:
    - name: Fail if matrix-nginx-proxy role already executed
      fail:
        msg: >-
          Trying to append node-exporter's reverse-proxying configuration to matrix-nginx-proxy,
          but it's pointless since the matrix-nginx-proxy role had already executed.
          To fix this, please change the order of roles in your playbook,
          so that the matrix-nginx-proxy role would run after the matrix-prometheus-node-exporter role.
      when: matrix_nginx_proxy_role_executed|default(False)|bool

    - name: Generate node-exporter metrics proxying configuration for matrix-nginx-proxy (matrix.DOMAIN/metrics/node-exporter)
      set_fact:
        matrix_prometheus_node_exporter_nginx_metrics_configuration_block: |
          location /metrics/node-exporter {
            {% if matrix_nginx_proxy_enabled|default(False) %}
              {# Use the embedded DNS resolver in Docker containers to discover the service #}
              resolver 127.0.0.11 valid=5s;
              set $backend "matrix-prometheus-node-exporter:9100";
              proxy_pass http://$backend/metrics;
            {% else %}
              {# Generic configuration for use outside of our container setup #}
              {# This may be implemented in the future. #}
              return 404 "matrix-nginx-proxy is disabled, so metrics are unavailable";
            {% endif %}
          }

    - name: Register node-exporter metrics proxying configuration with matrix-nginx-proxy (matrix.DOMAIN/metrics/node-exporter)
      set_fact:
        matrix_nginx_proxy_proxy_matrix_metrics_additional_system_location_configuration_blocks: |
          {{
            matrix_nginx_proxy_proxy_matrix_metrics_additional_system_location_configuration_blocks|default([])
            +
            [matrix_prometheus_node_exporter_nginx_metrics_configuration_block]
          }}
  when: matrix_prometheus_node_exporter_enabled|bool and matrix_prometheus_node_exporter_metrics_proxying_enabled|bool