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posts for march 2009.

wordpress dos-ing itself, and optimization.

march 1, 2009 at 07:20 by felix. six comments.

while updating some old posts with photos (just designwise, no content changed), i once again experienced a complete lockdown: the server became incredible slow and was floaded with apache processes, and i had to shut down and kill -9 all apache processes several times to be able to continue to do anything except waiting. this isn’t the first time this happend, but this time i had apache’s logging enabled (waiting for something like this) to see what was causing all the accesses. well, out of the 13.000 logfile entries (ranging over a week, i think), around 3.300 were by wordpress – and 99.9% of these happend in the last few hours, while i was updating the old posts. it seems that every time i updated a post, wordpress accesses all links and images in the post, also the local ones, and downloads them. yes, downloads them – also the big versions of panoramas. and if i’m updating posts with often 10–30 photos, some of them large, this clearly explains why the web server was dying. to put it that way, wordpress dosed itself. (the funny thing is that it did not first use a head first, to see what kind of link this is, but starts with a get to first download the whole thing. after downloading all links and images, it uses head on them.)
anyway. i don’t know at the moment what to do against that.
but another annoying thing is that the blog is loading rather slow. i also decided to see what is causing this. well, it turns out that the old main page was doing 298 sql queries. after disabling role scoper, this jumped down to 34, with loading times more or less the same. but then, i disabled the tag cloud. this just saved one query, but reduced the page generation time from around 10 to 2 seconds. wow. enabling role scoper again (i really need that one), i now have a bit less than 50 queries with maybe 4-5 seconds of page creation time.
well, still far from optimal, but already faster.

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