LVS and Varnish
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LVS and Varnish infrastructure
Notes
esams is representative of all cache-only sites; ulsfo is similar.
"upload" and "mobile" traffic operate similarly to "text" shown here.
When LVS balances traffic to the :80 varnishes directly for HTTP, it choses randomly. For :443 to the nginxes, it uses a hash of the client IP to help with SSL session persistence.
Within the caching layer (cp[1234]xxx machines), the jump from nginx to varnish:80 is direct on the local host only.
However, the jump from varnish:80 (frontend) to varnish:3128 (backend) is different: for that jump, we hash on the URL (etc) when balancing to the backends to divide the cache space among all machines, and thus the request typically moves from one machine to another within the cache layer here.