Varnish is a popular Web Load Balancer and here’s some commands that are useful to help diagnose your website’s performance, and give some stats and metrics about the response time and activity of your website as Varnish sees it:
// Query Times
varnishncsa -F '%t %{VCL_Log:Backend}x %Dμs %bB %s %{Varnish:hitmiss}x "%r"'
// Slow Queries
varnishncsa -F '%t %{VCL_Log:Backend}x %Dμs %bB %s %{Varnish:hitmiss}x "%r"' -m "VCL_Log:SlowQuery"
// Top URLs
varnishtop -i RxURL
// Top Referer, User-Agent, etc.
varnishtop -i RxHeader -I Referer
varnishtop -i RxHeader -I User-Agent
// Cache Misses
varnishtop -i TxURL
// awesome dashboard
varnishstat
FYI,
Richard.