From 6906b275ef58c5d35bef73fd64054925e9a7fa15 Mon Sep 17 00:00:00 2001
From: Will Szumski <will@stackhpc.com>
Date: Mon, 14 Dec 2020 18:29:21 +0000
Subject: [PATCH] Switch prometheus to active/passive mode

This uses the same approach as the mariadb role (and others).

Closes-Bug: #1928193
Co-Authored-By: John Garbutt <johng@stackhpc.com>
Change-Id: I79a7a8c80327cfd9ef31d17fe71f450a181a638c
---
 ansible/roles/prometheus/defaults/main.yml          |  7 +++++++
 .../prometheus-active-passive-be4fb033493e958f.yaml | 13 +++++++++++++
 2 files changed, 20 insertions(+)
 create mode 100644 releasenotes/notes/prometheus-active-passive-be4fb033493e958f.yaml

diff --git a/ansible/roles/prometheus/defaults/main.yml b/ansible/roles/prometheus/defaults/main.yml
index b1c1174609..5e9ecdf916 100644
--- a/ansible/roles/prometheus/defaults/main.yml
+++ b/ansible/roles/prometheus/defaults/main.yml
@@ -15,6 +15,7 @@ prometheus_services:
         mode: "http"
         external: false
         port: "{{ prometheus_port }}"
+        custom_member_list: "{{ prometheus_haproxy_members.split(';') }}"
   prometheus-node-exporter:
     container_name: prometheus_node_exporter
     group: prometheus-node-exporter
@@ -100,6 +101,12 @@ prometheus_services:
 ####################
 prometheus_mysql_exporter_database_user: "{% if use_preconfigured_databases | bool and use_common_mariadb_user | bool %}{{ database_user }}{% else %}prometheus{% endif %}"
 
+####################
+# HAProxy
+####################
+prometheus_active_passive: true
+prometheus_haproxy_members: "{% for host in groups['prometheus'] %}server {{ hostvars[host].ansible_facts.hostname }} {{ 'api' | kolla_address(host) }}:{{ prometheus_port }} check inter 2000 rise 2 fall 5{% if not loop.first %}{% if prometheus_active_passive | bool %} backup{% endif %}{% endif %};{% endfor %}"
+
 ####################
 # Blackbox
 ####################
diff --git a/releasenotes/notes/prometheus-active-passive-be4fb033493e958f.yaml b/releasenotes/notes/prometheus-active-passive-be4fb033493e958f.yaml
new file mode 100644
index 0000000000..54eb22c8aa
--- /dev/null
+++ b/releasenotes/notes/prometheus-active-passive-be4fb033493e958f.yaml
@@ -0,0 +1,13 @@
+---
+upgrade:
+  - |
+    Prometheus has been switched to active/passive mode. This is enabled by
+    default but can be turned off by setting ``prometheus_active_passive`` to
+    ``no``.
+    See bug `1928193
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1928193>`__.
+fixes:
+  - |
+    Fixes an issue with misaligned data points in grafana when loadbalancing
+    over multiple prometheus server instances. See bug `1928193
+    <https://bugs.launchpad.net/kolla-ansible/+bug/1928193>`__.