This documentation only applies to Varnish Customer Statistics 4.0.
Varnish Custom Statistics gives you granular and detailed cache and performance metrics on the contents of your cache and its associated traffic.
VCS produces real-time aggregated statistics from a group of Varnish servers. The statistics produced are then grouped according to keys defined in VCL and presented in time series.
VCS is split into 2 components:
vstatdserver. This component is the main database, UI, and API server for VCS. This should be installed on a separate server.
vstatdprobe. This component is installed on each of your Varnish servers. They connect and push data to the