You don't need to list them anywhere for this to work. They set up the necessary communication on their own by making use of watch-notify. On Mon, Jan 19, 2015 at 6:55 PM ZHOU Yuan <dunk...@gmail.com> wrote:
> Thanks Greg, that's a awesome feature I missed. I find some > explanation on the watch-notify thing: > http://www.slideshare.net/Inktank_Ceph/sweil-librados. > > Just want to confirm, it looks like I need to list all the RGW > instances in ceph.conf, and then these RGW instances will > automatically do the cache invalidation if necessary? > > > Sincerely, Yuan > > > On Mon, Jan 19, 2015 at 10:58 PM, Gregory Farnum <g...@gregs42.com> wrote: > > On Sun, Jan 18, 2015 at 6:40 PM, ZHOU Yuan <dunk...@gmail.com> wrote: > >> Hi list, > >> > >> I'm trying to understand the RGW cache consistency model. My Ceph > >> cluster has multiple RGW instances with HAProxy as the load balancer. > >> HAProxy would choose one RGW instance to serve the request(with > >> round-robin). > >> The question is if RGW cache was enabled, which is the default > >> behavior, there seem to be some cache inconsistency issue. e.g., > >> object0 was cached in RGW-0 and RGW-1 at the same time. Sometime later > >> it was updated from RGW-0. In this case if the next read was issued to > >> RGW-1, the outdated cache would be served out then since RGW-1 wasn't > >> aware of the updates. Thus the data would be inconsistent. Is this > >> behavior expected or is there anything I missed? > > > > The RGW instances make use of the watch-notify primitive to keep their > > caches consistent. It shouldn't be a problem. > > -Greg >
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