After investigation I have found the course- multiple
comparisons were called at the same time.
Not the best solution, but you could use a wrapper not to start a
comparison if there is already some diff3 running.
4. Memcache wherever it's possible (not all
servers have memcache)
memcache is a distributted cache. All servers cache to all memcached
(different items can go to different memcached). If you're using the
servers go only to 'its memcached', you're using it wrong.
2. faces a similar problem. After I edited my
rebots.txt, I discovered that
some clowns are ignoring my robots.txt.
Place link traps for bad robots / Block by user agent.
Also, only Google supports regular
expression in robots.txt, so I can't just use Disallow: *diff=* .
You can move to nice urls, so you can block index.php on robots.txt