r/collectd: Enable unixsock plugin

The *unixsock* plugin for *collectd* provides a socket-based interface
that other software can use to communicate with *collectd*.  Notably,
this can be used to publish custom values, query existing values, and
flush caches.

The socket is created at `/run/collectd/socket`.  The `/run/collectd`
directory is managed by systemd; it will be created automatically when
the service starts and cleaned up when it stops.

roles/collectd/defaults/main.yml

@@ -6,3 +6,5 @@ collectd_network_listen: []
 collectd_disable_plugins: []
 
 collectd_df: {}
+
+collectd_load_unixsock_plugin: true

roles/collectd/files/collectd-runtime-dir.conf

@@ -0,0 +1,2 @@
+[Service]
+RuntimeDirectory=collectd

roles/collectd/handlers/main.yml

@@ -1,3 +1,8 @@
+- name: reload systemd
+  systemd:
+    daemon_reload: true
+  changed_when: true
+
 - name: restart collectd
   service:
     name: collectd

roles/collectd/tasks/main.yml

@@ -23,6 +23,16 @@
   tags:
   - collectd-config
 
+- name: ensure collectd unixsock plugin is configured
+  template:
+    src: collectd-unixsock.conf.j2
+    dest: /etc/collectd.d/unixsock.conf
+    mode: 'u=rw,go=r'
+  notify: restart collectd
+  tags:
+  - collectd-config
+  - collectd-unixsock
+
 - name: ensure collectd network plugin is configured
   template:
     src: collectd-network.conf.j2
@@ -44,6 +54,20 @@
   - collectd-config
   - collectd-processes
 
+- name: ensure collectd systemd unit extension directory exists
+  file:
+    path: /etc/systemd/system/collectd.service.d
+    mode: 'u=rwx,go=rx'
+    state: directory
+- name: ensure collectd.service runtime directory is configured
+  copy:
+    src: collectd-runtime-dir.conf
+    dest: /etc/systemd/system/collectd.service.d/runtime-dir.conf
+    mode: 'u=rw,go=r'
+  notify:
+  - reload systemd
+  - restart collectd
+
 - name: ensure collectd starts at boot
   service:
     name: collectd

roles/collectd/templates/collectd-unixsock.conf.j2

@@ -0,0 +1,18 @@
+{% if collectd_load_unixsock_plugin %}
+LoadPlugin unixsock
+{% endif %}
+
+<Plugin unixsock>
+    SocketFile "/run/collectd/socket"
+{% if collectd_unixsock_group|d %}
+    SocketGroup "{{ collectd_unixsock_group }}"
+{% endif %}
+{% if collectd_unixsock_perms|d %}
+    SocketPerms "{{ collectd_unixsock_perms }}"
+{% endif %}
+{% if collectd_unixsock_delete|d is true %}
+    DeleteSocket true
+{% elif collectd_unix_sock_delete|d is false%}
+    DeleteSocket false
+{% endif %}
+</Plugin>