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

---

- when: matrix_prometheus_node_exporter_enabled | bool and matrix_prometheus_node_exporter_metrics_proxying_enabled | bool
  block:
    - name: Fail if matrix-nginx-proxy role already executed
      ansible.builtin.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)
      ansible.builtin.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;
            {% elif matrix_prometheus_node_exporter_matrix_nginx_proxy_not_enabled_proxy_pass_host != '' %}
              proxy_pass http://{{ matrix_prometheus_node_exporter_matrix_nginx_proxy_not_enabled_proxy_pass_host }}/metrics;
            {% else %}
              return 404 "matrix-nginx-proxy is disabled and no host port was bound to the container, so metrics are unavailable";
            {% endif %}
          }

    - name: Register node-exporter metrics proxying configuration with matrix-nginx-proxy (matrix.DOMAIN/metrics/node-exporter)
      ansible.builtin.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]
          }}