Saturday, December 31st, 2005

Harry Potter and the Spiral of Death (Note: 3AM downtime)

Sorry for the slow-down in the last 36 hours. There was a database issue. Recommendations weren’t being cached right, so it had to remake them every time. That took a lot of processing power. For example, to produce a recommendation for one of the Harry Potter books it had to retrieve and do math on the libraries of nearly half of of all LibraryThing! And when a page doesn’t come up immediately many users hit refresh over and over—the spiral of death.

I fixed the immediate problem, but it will be a little while before the cache is full again. I’m going to fix the larger problem by adding a second, “thinking” server, that will get a new copy of the book data ever night and sit around all day thinking about recommended books, related tags and so forth. LibraryThing’s slowness—when it’s slow—is all about these tasks. Looking at your catalog, adding books and so forth don’t tax it much. I also like the idea of a server that sits around all day thinking about books. It might even develop opinions.

Finally, I’m going to make some more tweaks at 3am EST tonight. This means that people in California will not be able to add books while watching Dick Clark’s New Year’s Rockin’ Eve. For this I apologize.

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