Implement dovecot mail plugin, configure limits

This also moves custom plugins into the `roles/munin/templates/plugins`
directory, which should hopefully be easier to maintain than the
existing inline dictionary. The only issue is that now it is a bit
harder to deal with the filepaths.

This change has already been deployed.

ansible/roles/munin/tasks/main.yml

@@ -33,6 +33,18 @@
   notify:
     - Restart munin-node service
 
+- name: Template munin plugin configuration file
+  template:
+    src: plugin.conf.j2
+    dest: /etc/munin/plugin-conf.d/custom
+    owner: root
+    group: root
+    mode: "0444"
+  tags:
+    - role::munin
+  notify:
+    - Restart munin-node service
+
 - name: Enable non-default munin plugins
   file:
     src: "/usr/share/munin/plugins/{{ item.src }}"
@@ -68,15 +80,17 @@
     - Restart munin-node service
 
 - name: Copy custom munin plugins
-  copy:
-    content: "{{ item.value }}"
-    dest: /etc/munin/plugins/{{ item.key }}
+  template:
+    src: "{{ item }}"
+    # Split two levels of file extensions
+    dest: "/etc/munin/plugins/{{ item | basename | splitext | first | splitext | first }}"
     owner: root
     group: root
     mode: "0555"
   loop_control:
-    label: "{{ item.key }}"
-  loop: "{{ munin_node_custom_plugins | dict2items }}"
+    # I love representing data modification logic in YAML!
+    label: "{{ item | basename | splitext | first | splitext | first }}"
+  with_fileglob: "../templates/plugins/*"
   tags:
     - role::munin
 

ansible/roles/munin/templates/plugin.conf.j2

@@ -0,0 +1,15 @@
+# Ansible managed
+
+[dovecot_maildirs]
+user root
+group vmail
+
+[load]
+env.load_warning {{ ansible_processor_nproc * 0.7 }}
+env.load_critical {{ ansible_processor_nproc * 0.85 }}
+
+[memory]
+env.apps_warning 70%
+env.apps_critical 90%
+env.swap_warning 60%
+env.swap_critical 80%

ansible/roles/munin/templates/plugins/dovecot_maildirs.sh.j2

@@ -0,0 +1,64 @@
+#!/bin/sh
+# Ansible managed
+
+cd /var/vmail || exit 1
+
+print_maildir_config() {
+    find . -maxdepth 1 -type d \
+        | tail -n +2 \
+        | awk -F / '{
+            print $2 ".draw AREASTACK"
+            print $2 ".label " $2
+        }'
+}
+
+if [ "$1" = "autoconf" ]; then
+    echo "no"
+    exit
+fi
+
+if [ "$1" = "config" ]; then
+    cat <<EOF
+multigraph dovecot_maildir_sizes
+graph_title Dovecot Maildir sizes
+graph_args --base 1024 -l 0
+graph_vlabel bytes
+graph_category mail
+graph_info Shows the sizes of top mail directories by their respective users
+graph_total Total
+graph_order joe jc
+EOF
+    print_maildir_config
+    cat <<EOF
+multigraph dovecot_maildir_mails
+graph_title Dovecot mails in maildirs
+graph_args --base 1000 -l 0
+graph_vlabel mails
+graph_category mail
+graph_info Shows the amount of mails by user on our Dovecot server
+graph_total Total
+graph_order joe jc
+EOF
+    print_maildir_config
+    exit 0
+fi
+
+echo "multigraph dovecot_maildir_sizes"
+du --bytes --summarize -- * \
+    | awk '{ print $2 ".value " $1 }'
+
+echo "multigraph dovecot_maildir_mails"
+find . \
+    | awk -F / '
+        # Maildir e-mails have the hostname contained in them
+        $0 ~ "{{ ansible_fqdn }}" {
+          total[$2] += 1
+        }
+        END {
+          for (user in total) {
+            print user ".value " total[user]
+          }
+        }
+    '
+
+# vim: ft=sh.jinja2:

ansible/roles/munin/templates/plugins/lovering_inheritance.py.j2

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+# Ansible managed
+
+import datetime
+import random
+import sys
+
+if sys.argv[-1] == "autoconf":
+    print("no")
+    sys.exit(0)
+
+if sys.argv[-1] == "config":
+
+    print("""\
+graph_title Lovering Inheritance
+graph_args --base 1000 -l 0
+graph_vlabel £
+graph_category people
+graph_info This graph shows the insurance that Chris can cash out.
+graph_total Total
+savings.label Savings
+savings.info Base inheritance money Chris paid into his account in 2024
+savings.draw AREASTACK
+interest.label Interest
+interest.info Amount of money gained from interest on the base amount
+interest.draw AREASTACK
+inherited.label Inherited money
+inherited.info Amount inherited from deaths of friends, family and victims
+inherited.draw AREASTACK\
+    """)
+    sys.exit(0)
+
+# Fixed seed to ensure that the bank jitter is constant
+random.seed(1234)
+today = datetime.date.today()
+savings = 740
+interest_per_day = 0.005
+insurance_policy_start = datetime.date(2024, 8, 28)
+days_griefed = (today - insurance_policy_start).days
+accrued_interest = 0
+for _ in range(days_griefed):
+    bank_jitter = random.random()
+    accrued_interest += bank_jitter * (interest_per_day * (savings + accrued_interest))
+
+inherited_money = 0
+
+if days_griefed > 10:
+    # Hassan declared as KIA (he had stocks in Big Oil)
+    inherited_money += 10000
+
+if days_griefed > 60:
+    # Death of Joe (prospect of sale of stolen GPUs)
+    inherited_money += 5000
+
+if days_griefed > 170:
+    # Bella disappears (spent all on chicken and gifts for his wife)
+    inherited_money += 300
+
+if days_griefed > 360:
+    # Lola Banks deploys her Titan missile but burns herself to death
+    inherited_money += 12000
+
+print(f"savings.value {savings}")
+print(f"interest.value {accrued_interest}")
+print(f"inherited.value {inherited_money}")
+
+# vim: ft=python.jinja2: