On 07/01/2009 05:39 PM, Mike McGrath wrote: > On Wed, 1 Jul 2009, Stephen John Smoogen wrote: > >> On Wed, Jul 1, 2009 at 6:08 PM, Mike McGrath<mmcgrath@xxxxxxxxxx> wrote: >>> On Wed, 1 Jul 2009, Stephen John Smoogen wrote: >>> >>>> On Wed, Jul 1, 2009 at 3:33 PM, Mike McGrath<mmcgrath@xxxxxxxxxx> wrote: >>>>> I'm not sure if we have any memcached experience on the list but I thought >>>>> I'd ask. Can anyone explain this: >>>>> >>>>> http://pastebin.ca/1481219 >>>>> >>>>> Notice how memcached1 has a much higher hit rate and memcached2 has a much >>>>> lower hit rate? >>>>> >>>> >>>> The time for memcached1 is 5x less than memcached2 being up. That can >>>> have an effect on caching as right after a system comes up its rates >>>> are usually much higher and then over time fall off (iirc). I think it >>>> would take bringing both up at the same time to figure out if there is >>>> a true disparity over caching. >>>> >>> >>> I thought that exact same thing :) >>> >>> memcahed1: >>> STAT uptime 9143 >>> STAT get_hits 311736 >>> STAT get_misses 11255 >>> >>> memcached2: >>> STAT uptime 9144 >>> STAT get_hits 49679 >>> STAT get_misses 11116 >>> >> >> Now that shows something not kosher. My guess is some app is not >> talking to both? What apps use memcached for what? >> > > I was just talking to ricky about this a bit in IRC. So here's the scoop. > > We've got mediawiki using memcached for a couple of things, including > session data (which is weird and wrong but fast). > > The recent addition to the group is Fedora community, specifically in it's > implementation of beaker. I'm going to get ahold of luke tomorrow to > verify and test some stuff but I think this line in the config: > > beaker.cache.url = memcached1;memcached > > I'm not sure how beaker reads that, but I suspect it might be only sending > information to memcached1 and ignoring memcached2 altogether. If this > theory holds it'd explain why memcached1 not only has a higher request > rate but also a higher hit rate because I suspect fedoracommunity requests > some of the same info over and over again compared to the wiki which > probably has a broader data pool it pulls from. > easy test: reverse that: beaker.cache.url = memcached2;memcached1 and see if the cache hit ratio reverses itself. -Toshio
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