Using Varnish as load balancer

Question

Varnish already support load balancing HTTP 1.1 and Web Socket requests, e.g. https://www.varnish-cache.org/trac/wiki/LoadBalancing

Since we already using Varnish for caching purpose, are there any benefit if we add nginx or ha proxy in front of Varnish for load balancing, or should we just use Varnish for load balancing?

Seems this approach is quite rare, and why?

What problem are you trying to solve, and why do you want to make your setup more complex? — Michael Hampton, Oct 09 '12 at 16:10

score 3 · Accepted Answer · answered Oct 09 '12 at 16:56

Disclaimer : I'm a varnish fanboy.

I'm not aware of people putting nginx in front of varnish : they sometimes do the opposite as nginx is supposed to be a lightweight webserver.

Unless I have a good reason not to do so, I would do the load balancing with varnish.

However using varnish for load balancing can be tricky :

You don't want varnish to be single point of failure so you think about 2 servers at least.
With active active setup you'll have to deal with cache consistency problem and set url purge in case of update.
With active passive setup, you'll have to deal with cache stampeding.

The fact that varnish does not do https, while nginx does, is the reason I put nginx in front of varnish sometimes. — arjarj, Oct 09 '12 at 18:22

Using Varnish as load balancer

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