On Fri, Jan 15, 2010 at 5:33 PM, pub crawler <[email protected]>wrote:
Varnish performs very well. Extending this to have a cluster > functionality within Varnish I think just makes sense. haproxy and F5 equipment also both perform very well. > The workaround > solutions so far seem to involve quite a bit of hardware as well as > having a miss rate of 50% in example of 2 Varnish instances. Sure it > can hot populate fast, but it's two stacks of memory wasted for the > same data per se. If you hash your requests from a load balancer across a pool of n varnish instances, the most you lose in the event of a failure is 1/n. You don't cache objects in more than one instance. There's no "wasted" memory. I suppose a custom solution to hash the inbound > requests somehow and determine which Varnish should have the data can > be done, but unsure if anyone now is doing that. > That's precisely what L7 switches do. As David said, haproxy has this functionality, as do other implementations. > Squid is a total disaster. If it wasn't none of us would be here > using Varnish now would we :) It's amazing Squid even works at this > point. > Can you quantify this statement? Squid works very well at some installations. It's not like the code that was out there working spontaneously started to become buggier. > I put in a feature request this evening for this functionality. We'll > see what the official development folks think. If it can't be > included in the core, then perhaps a front-end Varnish proxy is in > order developmentally. I'll say this akin to Moxi in front of > memcached instances: http://labs.northscale.com/moxi/ I'm all for putting backend hashing into Varnish for the purpose of routing requests to backends based on a consistent hash of the request parameters -- and there's no reason why the backend can't be another Varnish instance. But the appropriate use of this is to more efficiently utilize cache memory by associating an object with a designated Varnish server in a pool, not for HA. This was one of my first requests that still (alas) has seen no traction. --Michael
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