r/collectd-version: Add OS version plugin

The `collectd-version` script uses the *collectd* UNIX socket to send
custom values to *collectd* to track the OS version.  Since these values
obviously cannot change while the system is running, the values are
specified with a very long interval.  This avoids having to continuously
insert the values, either with a long-running process or by repeatedly
running a script.  The values only need to be inserted once when
*collectd* starts.

collectd.yml

@@ -3,6 +3,9 @@
   - role: collectd
     tags:
     - collectd
+  - role: collectd-version
+    tags:
+    - collectd-version
 
 - hosts: collectd-prometheus
   roles:

roles/collectd-version/files/collectd-version.py

@@ -0,0 +1,51 @@
+#!/usr/bin/python3
+import os
+import shlex
+import socket
+
+
+SECONDS = 1
+MINUTES = 60 * SECONDS
+HOURS = 60 * MINUTES
+DAYS = 24 * HOURS
+
+COLLECTD_SOCKET = os.environ.get('COLLECTD_SOCKET', '/run/collectd/socket')
+COLLECTD_INTERVAL = int(os.environ.get('COLLECTD_INTERVAL', 365 * DAYS))
+
+
+def parse_os_release():
+    data = {}
+    with open('/etc/os-release', encoding='utf-8') as f:
+        for line in f:
+            line = line.split('#')[0].strip()
+            if not line:
+                continue
+            key, __, value = shlex.split(line)[0].partition('=')
+            if not key or not value:
+                continue
+            data[key] = value
+    return data
+
+
+def get_values():
+    osinfo = parse_os_release()
+    if 'PRETTY_NAME' in osinfo:
+        yield 'name', osinfo['PRETTY_NAME']
+    if 'VERSION_ID' in osinfo and 'ID' in osinfo:
+        yield osinfo['ID'], osinfo['VERSION_ID']
+    yield 'kernel', os.uname().release
+
+
+def main():
+    hostname = socket.getfqdn()
+    sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    sock.connect(COLLECTD_SOCKET)
+    with sock:
+        for valtype, value in get_values():
+            identifier = f'{hostname}/version-{value}/version-{valtype}'
+            line = f'PUTVAL "{identifier}" interval={COLLECTD_INTERVAL} N:1\n'
+            sock.send(line.encode('utf-8'))
+
+
+if __name__ == '__main__':
+    main()

roles/collectd-version/files/collectd-version.service

@@ -0,0 +1,11 @@
+[Unit]
+Description=collectd version plugin
+BindsTo=collectd.service
+After=collectd.service
+
+[Service]
+ExecStart=/usr/local/libexec/collectd-version
+RemainAfterExit=true
+
+[Install]
+WantedBy=collectd.service

roles/collectd-version/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: restart collectd-version
+  service:
+    name: collectd-version
+    state: restarted

roles/collectd-version/tasks/main.yml

@@ -0,0 +1,32 @@
+- name: ensure collectd-version script is installed
+  copy:
+    src: collectd-version.py
+    dest: /usr/local/libexec/collectd-version
+    mode: 'u=rwx,go=rx'
+  notify: restart collectd
+  tags:
+  - install
+
+- name: ensure collectd-version.service systemd unit exists
+  copy:
+    src: collectd-version.service
+    dest: /etc/systemd/system/
+    mode: 'u=rw,go=rx'
+  notify:
+  - reload systemd
+  - restart collectd-version
+  tags:
+  - systemd
+
+- name: ensure collectd-version service starts automatically
+  service:
+    name: collectd-version
+    enabled: true
+  tags:
+  - service
+- name: ensure collectd-version service is started
+  service:
+    name: collectd-version
+    state: started
+  tags:
+  - service