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Transcript of Memcached
MemcachedNodes nodes = ...
int index = key.hashcode() % nodes.length
There are other hash algorithms and NodeLocator classes, but this appears to be the default How it works (Client) What this means for us? It's important to have the same cache servers configured for all nodes for a given app.
If different apps wants to use the same cache key, then they must also use the same list of cache servers. Also note that spymemache's add/get/set methods are asynchronous. But npg-commons hides this for us. How we use it We have 2 instaces of Memcached running on 2 different servers (npgcache1 and npgcache2) Some stats (after being up for 45 days): npgcache1 Gets received npgcache2 Get hits Hit rate Sets received Evictions
listen_disabled_num 642699085 636601272 99.05% 8135875 0 0 574944800 568810705 97.4% 7891189 0
0 npgcache1 gets used slightly more than npgcache2 (52.78% of gets go to it) How we use it How big are the things we store in Memcached?? How we use it ... but of that, what do we actually use?? Used bytes Max bytes Memory usage 965062213 12884901888 7.5% 900020612 12884901888 7% How we use it Conclusion: We have a high hit rate, plenty of memory, no evictions, an even split between the instances and is always listening for new connections. There doesn't appear to be any obvious config problems... Possible Improvements There doesn't appear to be any improvements to be gained by changing configuration. But how about in changing Memcached and the client itself? We currently use Memcached 1.4.5 and Spymemcached 2.6. Would things improve if we use Memcached 1.4.15 and Spymencached 2.8.4?