[openstack-dev] Why doesn't Swift cache object data?

Clint Byrum clint at fewbar.com
Sat Jun 27 00:28:22 UTC 2015

Excerpts from 杨苏立 Yang Su Li's message of 2015-06-25 17:35:18 -0700:
> Thanks a lot for your answer.
> I guess that is an excellent answer on "why does swift explicitly disable
> object data caching at the page cache level". But my question is a bit
> different "Why doesn't swift use memcached to cache object data?" Not that
> it is a bit different than implementing it yourself at the proxy server.
> All you need to do is to write a middleware to talk to the memcached
> cluster, and swift already does that for account info etc.
> Is it because of the potential consistency issue? Or maybe you assume your
> clients already have caching solution on top of Swift (like vanish, as you
> mentioned. But that's very specific to http caching...)

I believe John answered this very clearly. This middleware exists,
and it is entirely enabled by HTTP's very well understood notion of
caching. There is zero point to writing a memcached middleware that will
try to match what varnish or squid can do.

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