Zero-Downtime Servicing of a Varnish Server Behind a F5 BIG-IP

[Steven Engelhardt]

I have two Varnish servers behind a F5 BIG-IP load balancer.  Both servers
are constantly active and serving ~5,000 requests/second 24x7.  Clients
aggressively use HTTP 1.1 Keep-Alives.

I'm looking to develop a process for servicing and upgrading the Varnish
servers which results in 0 downtime to the client.  Our normal process for
performing changes on production servers is:
1. Mark the server as disabled in the BIG-IP
2. Wait for the connections on the server to drop to 0
3. Service the machine

However, because of the aggressive and constant use of HTTP Keep-Alives,
clients virtually never drop their connections, and the machine continues
to serve traffic for quite a long time after it is disabled in the BIG-IP.

Is there a way to tell Varnish to aggressively close all client HTTP
connections?

Thank you,
Steve

-- 
Steven Engelhardt
sengelha at gmail.com
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