From 8cab0b368e24e43c81b176f004e81e8d7e2c86b3 Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Wed, 3 Aug 2022 21:01:32 -0500
Subject: [PATCH] r/collectd: Ignore overlay filesystems

By default, the *df* pluggin for collectd, which monitors filesystem
usage, collects data about all mounted filesystems.  It can be
configured to ignore some filesystems, either by mount point, device, or
filesystem type.  We will uses this capability to avoid collecting data
about OverlayFS mounts, because by definition, they do not represent a
real filesystem, but one or more other mounted filesystems.  Collecting
data about these just creates useless metrics, especially on machines
that run containers.
---
 roles/collectd/defaults/main.yml             |  2 ++
 roles/collectd/tasks/main.yml                | 10 ++++++++++
 roles/collectd/templates/collectd-df.conf.j2 |  8 ++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 roles/collectd/templates/collectd-df.conf.j2

diff --git a/roles/collectd/defaults/main.yml b/roles/collectd/defaults/main.yml
index 47b1798..ea06caa 100644
--- a/roles/collectd/defaults/main.yml
+++ b/roles/collectd/defaults/main.yml
@@ -2,6 +2,8 @@ collectd_default_config: true
 collectd_load_network_plugin: false
 collectd_network_servers: []
 collectd_network_listen: []
+collectd_df_ignore_fstype:
+- overlay
 
 collectd_plugins: {}
 
diff --git a/roles/collectd/tasks/main.yml b/roles/collectd/tasks/main.yml
index cf569de..38119a5 100644
--- a/roles/collectd/tasks/main.yml
+++ b/roles/collectd/tasks/main.yml
@@ -50,6 +50,16 @@
   - collectd-config
   - collectd-typesdb
 
+- name: ensure collectd df plugin is configured
+  template:
+    src: collectd-df.conf.j2
+    dest: /etc/collectd.d/df.conf
+    mode: 'u=rw,go=r'
+  notify: restart collectd
+  tags:
+  - collectd-config
+  - collectd-df
+
 - name: ensure collectd unixsock plugin is configured
   template:
     src: collectd-unixsock.conf.j2
diff --git a/roles/collectd/templates/collectd-df.conf.j2 b/roles/collectd/templates/collectd-df.conf.j2
new file mode 100644
index 0000000..53d8925
--- /dev/null
+++ b/roles/collectd/templates/collectd-df.conf.j2
@@ -0,0 +1,8 @@
+{% if collectd_df_ignore_fstype %}
+<Plugin df>
+{% for fstype in collectd_df_ignore_fstype %}
+    FSType {{ fstype }}
+{% endfor %}
+    IgnoreSelected true
+</Plugin>
+{% endif %}