Facebook engineering notes on Scaling Out. Jason Sobel explains a couple of tricks Facebook use to deal with consistency between their California and Virginia data centres. The first is to hijack the MySQL replication stream to include information about memcached records to invalidate; the second is to use Layer 7 load balancers which inspect a “last modification time” cookie and send users to the masters in California if they have updated their profile in the past 20 seconds.
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So, I'm left wondering how they magically know which keys are invalidated by updates.
Also, the REPLACE INTO syntax was new to me-- of course, I've never used MySQL in anger.
Jeremy Dunck - 21st August 2008 17:20 - #
No magic - they added syntax to MySQL to allow queries to include a list of keys that are invalidated by the query.