update rules comments

Author: sjpb

ansible/roles/alertmanager/README.md

@@ -24,6 +24,8 @@ In general usage may only require:
 - Enabling the Slack integration (see section below).
 - Possibly setting `alertmanager_web_external_url`.
 
+TODO: explain where alertmanager web GUI is
+
 ## Role variables
 
 All variables are optional. See [defaults/main.yml](defaults/main.yml) for
@@ -156,3 +158,7 @@ Some ideas for future alerts which could be useful:
 - smartctl-exporter-based rules for baremetal nodes where the is no
   infrastructure-level smart monitoring
 - loss of "up" network interfaces
+
+
+TODO: suggest awesome alerts
+TODO: note that child env rule files override parent envs

environments/common/inventory/group_vars/all/prometheus.yml

@@ -15,10 +15,10 @@ prometheus_alertmanager_config_default:
         - "{{ alertmanager_address }}:{{ alertmanager_port }}"
 prometheus_alertmanager_config: "{{ prometheus_alertmanager_config_default if groups['alertmanager'] else {} }}"
 
-# by default, use rule files from the following path relative to current and all parent environment inventory directories:
+# By default, find rule files from the following path relative to current and all parent environment inventory directories:
+# Note: If the same file exists in parent and child environments, only the file in the latter has any effect.
 prometheus_alert_rules_files_inventory_glob: ../files/prometheus/rules/*.rules
 prometheus_alert_rules_files: "{{ ansible_inventory_sources | product([prometheus_alert_rules_files_inventory_glob]) | map('join', '/') | map('realpath') }}"
-# TODO: find a way to include/exclude files?
 
 prometheus_alert_rules: []