it doesnt imho but i may be wrong. libketama its an old lib of last.fm. PECL lib implements its own might be based on libketama.
On Fri, Feb 27, 2009 at 7:10 PM, Henrik Schröder <[email protected]> wrote: > That is really weird, since the only difference between naive and > consistent server selection is that for the consistent one, you > pre-calculate an array of integers that holds 100 values per server during > startup, and for your actual server selection, you do a binary search into > this array with your hashed key, but that's a really trivial operation. > > However, I seem to remember that the PHP client uses an external C library, > libketama or something, for doing the consistent server selection, this > might cause a big overhead in your case compared to doing the naive > selection which is probably implemented straight in PHP. I know that for the > Perl clients, there's one in pure Perl, and one that also uses libketama, > maybe there's something similar for PHP? > > > /Henrik > > > On Fri, Feb 27, 2009 at 15:50, Pavel Aleksandrov <[email protected]>wrote: > >> >> Hello, I am working for a big web site. We have around 9000 hits/s on >> our MySQL replication trees and 500 000 unique visitors each day, just >> to give a clue about the load we are experiencing. We run on MySQL, >> Apache2, Gentoo, PHP 4 + PECL Memcache module. We've been using a >> single 12G memcached instance for speeding up things (we've reached >> the point where we can't solely rely on our DB). Using a single >> instance is not what memcached is meant for, so we decided to scale >> things up a bit, so we added 12 more instances, 2G each (32 bit >> servers, 4 instances per server, 3 servers). Then we switched from the >> "standard" (naive) method of hash distribution to the "consistent" >> method. >> >> What happened was that the load on our web nodes (we have 3 of them) >> went up about 3 times the usual. I'm guessing it's the new hash >> distribution method that's doing this. Am I missing something or using >> this method is always so CPU intensive? Do we have another choice or >> we should invest in more web nodes, to distribute the new load if we >> decide to stick to the consistent hashing algorithm? > > >
