Add plugin for Varnish 4

plugins/varnish4/README.md

@@ -0,0 +1,31 @@
+Munin Plugin for Varnish 4
+==========================
+
+Modified version of the plugin for Varnish 2/3 from the munin distribution
+to adapt to the XML output of Varnish 4 varnishstat.
+
+Installation
+------------
+
+- Copy varnish4_ to the Munin plugins directory
+- Replace @@PERL@@ with the path to the perl executable
+- Make varnish_ runnable
+
+Configuration
+-------------
+
+Run ``munin-node-configure --shell`` and link the aspects to monitor to
+your actual plugins directory.
+
+In your plugins.conf add
+```
+[varnish4_*]
+     env.varnishstat varnishstat
+     env.name
+```
+``env.varnishstat`` can be a full path to varnishstat if it's
+not in the path already.
+
+``env.name is blank`` (undefined) by default and can be used to specify a -n
+name argument to varnish if multiple instances are running on the same
+server.