Improve keepalived alert script and add some comments

At the ICPC WFs in Egypt the correct sound card to use is 0;
just try to set the volume on both 0 and 1. Also try beep and send
a desktop notification.

Author: DOMjudge team

Diff for: provision-contest/ansible/roles/keepalived/files/alerting/bin/alerting.sh.template

@@ -1,7 +1,16 @@
-#!/bin/sh
+#!/bin/bash
 
+# Try a couple of different notification methods.
+
+notify-send -u critical -t 60000 "Alert: keepalived status changed at $(date '+%T') !"
+
+amixer -c 0 set Master 100%
 amixer -c 1 set Master 100%
 
 for i in 1 2 3 4 5 6 7 8 9 10 ; do
     aplay /usr/share/sounds/sound-icons/pipe.wav
 done
+
+beep -f  500 -l 400 -d 100 -r 4
+beep -f 1000 -l 400 -d 100 -r 4
+beep -f  500 -l 200 -d 100 -r 6

Diff for: provision-contest/ansible/roles/keepalived/files/alerting/bin/trigger_alert.sh

@@ -1,2 +1,7 @@
 #!/bin/sh
+
+# This only copies the script below which contains alerting code
+# A desktop autostart application started the alert_listener.sh
+# script, which then detects the copy and executes it.
+
 cp ~/bin/alerting.sh.template ~/alerting.sh

Diff for: provision-contest/ansible/roles/keepalived/tasks/main.yml

@@ -1,11 +1,12 @@
 ---
 # These tasks install keepalived with IP failover
 
-- name: Install keepalived
+- name: Install keepalived and beep (for alerting)
   apt:
     state: present
     pkg:
       - keepalived
+      - beep
 
 - name: Configure keepalived for domjudge IP failover
   template: