@WeiZhong Got around today to run approach0 on my linux virtualbox and managed to make running webserver with everything, so good documentation! (and I am not linux user at all). I've tried it so far only the public repository and few indexed pages from MSE, but now that it is running I can play with it more and understand how it works etc... I will probably try to make few more crawlers to include mathoverflow as well, do you remember what were the sizes of crawled/index data for AoPS+MSE?