prometheus: add extra_args support for custom prometheus command-line flags

Author: djooberlee

prometheus/pillar.example

@@ -16,7 +16,8 @@ prometheus:
         - name: prod
           port: 9090 # docker published port, nginx will forward /prod to it
           image: prom/prometheus
-          #retention_time: 30d # optional
+          extra_args: '--web.enable-remote-write-receiver' # optional, extra command-line flags appended to prometheus container command
+          retention_time: 30d # optional
           auth:
             - developer1: password1
             - developer2: password2

prometheus/prometheus.sls

@@ -297,7 +297,12 @@ prometheus_container_{{ loop.index }}_{{ i_loop.index }}:
       {% else %}
         {% set retention_time_arg = '' %}
       {% endif %}
-    - command: --config.file=/prometheus-data/etc/prometheus.yml --storage.tsdb.path=/prometheus-data {{ retention_time_arg }} --web.external-url=https://{{ domain['name'] }}/{{ instance['name'] }}/ --web.enable-admin-api
+      {% if instance['extra_args'] is defined and instance['extra_args'] is not none %}
+        {% set extra_args = instance['extra_args'] %}
+      {% else %}
+        {% set extra_args = '' %}
+      {% endif %}
+    - command: --config.file=/prometheus-data/etc/prometheus.yml --storage.tsdb.path=/prometheus-data {{ retention_time_arg }} --web.external-url=https://{{ domain['name'] }}/{{ instance['name'] }}/ --web.enable-admin-api {{ extra_args }}
 
 prometheus_container_restart_{{ loop.index }}_{{ i_loop.index }}:
   cmd.run:
@@ -539,4 +544,3 @@ nginx_reload_cron:
     - hour: 6
 
 {% endif %}
-