This is a Zabbix template + discovery & sender script useful to monitor Varnish Cache >= 4.0 instances:

1. Copy zabbix-varnish-cache.py to /usr/local/bin/.

2. If using Varnish Cache >= 4.1, add zabbix user to the varnish group:

   $ sudo usermod -a --groups varnish zabbix
   

3. Grant sudo permissions to the zabbix user to execute the /usr/local/bin/zabbix-varnish-cache.py script. This is not mandatory but it's recommended in order to let the script execute varnishadm commands used to discover the current active VCL, discover healthiness of each backend, etc.

4. Add the varnish.discovery user parameter to Zabbix:

   UserParameter=varnish.discovery[*],sudo /usr/local/bin/zabbix-varnish-cache.py -i '$1' discover $2
   

5. Add a new job to the zabbix user crontab (beware of the -i and -s options). This will submit Varnish Cache metrics through Zabbix Sender:

   * * * * * /usr/local/bin/zabbix-varnish-cache.py -i '' send -c /etc/zabbix/zabbix_agentd.conf -s dev > /dev/null 2>&1
   

6. Import the Varnish Cache template (template-app-varnish.xml file).

7. Add an existing / new host to the Varnish Cache servers group and link it to the Template App Varnish Cache template. Beware you must set a value for the {$VARNISH_CACHE_LOCATIONS} macro (comma-delimited list of Varnish Cache instance names). Usually you should leave its value blank when running a single Varnish Cache instance per server.

8. Adjust triggers and trigger prototypes according with your preferences.