Agree that there are pros and cons to caching at different layers. As for plugins, in most places where we support memcache we revert to an in-memory cache if it isn't configured.
The work that was done during essex was to make the metadata service use either an external cache or internal cache. When an cloud-init based image boots it makes dozens of calls to get data, which results in dozens of RPC calls to nova-network to map IP to instance and then to the DB to load data. --------- Background info: The in-process cache I commited is actually the code previously known as the "fake" memcache, moved from nova/tests to nova/common. The reason for the move is two-fold: 1) the code was already in use as an in-memory cache in other locations in the code 2) nova/tests isn't included in most (all?) packagings. Also Josh Harlow has been researching better alternatives for in-memory caches for python (rather than re-inventing the wheel - which I started here: https://github.com/cloudbuilders/millicache ...) ---------- So ya, I think a summit proposal would be good. Jesse On Thu, Mar 22, 2012 at 8:06 AM, Sandy Walsh <[email protected]> wrote: > o/ > > Vek and myself are looking into caching strategies in and around Nova. > > There are essentially two approaches: in-process and external (proxy). > The in-process schemes sit in with the python code while the external > ones basically proxy the the HTTP requests. > > There are some obvious pro's and con's to each approach. The external is > easier for operations to manage, but in-process allows us greater > control over the caching (for things like caching db calls and not just > HTTP calls). But, in-memory also means more code, more memory usage on > the servers, monolithic services, limited to python based solutions, > etc. In-process also gives us access to tools like Tach > https://github.com/ohthree/tach for profiling performance. > > I see Jesse recently landed a branch that touches on the in-process > approach: > https://github.com/openstack/nova/commit/1bcf5f5431d3c9620596f5329d7654872235c7ee#nova/common/memorycache.py > > I don't know if people think putting caching code inside nova is a good > or bad idea. If we do continue down this road, it would be nice to make > it a little more modular/plug-in-based (YAPI .. yet another plug-in). > Perhaps a hybrid solution is required? > > We're looking at tools like memcache, beaker, varnish, etc. > > Has anyone already started down this road already? Any insights to > share? Opinions? (summit talk?) > > What are Glance, Swift, Keystone (lite?) doing? > > -S > > _______________________________________________ > Mailing list: https://launchpad.net/~openstack > Post to : [email protected] > Unsubscribe : https://launchpad.net/~openstack > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~openstack Post to : [email protected] Unsubscribe : https://launchpad.net/~openstack More help : https://help.launchpad.net/ListHelp
