Most of the reasoning is documented in the big comment. In short, we tried
to solve the problem with caching, but the caching should hardly be necessary
now that the bottleneck should be fixed. We'll see on production if it
actually solves the whole problem, but I've confirmed in the console that
redefining this function makes random_basic_per_species (as called during
rendering) a ton faster. And this way we keep our randomness, woo!
This is a surprisingly huge performance gain. On my testing (with
cache_classes set to true to also cache templates), this sped up
closet_hangers#index rendering by a factor of 2 when there were a
significant number of items. Cool beans.
I think we can even hold off on the individual hanger caching now:
we've made the closet hanger partial tons faster by moving forms out
of them and doing this cache check earlier. I'm expecting significant
performance gains both here and on items#index (though less so there).
I'll deploy and see how much it helps in production; if not enough, we
can look at the layered caching of hangers, lists, groups, full pages,
etc.
So glad we don't *have* to move to a pagination model!
We lose no-JS support, which I kinda miss, but caching is gonna be more
important down the line. Delete form moves next, then we cache.
CSRF token changes: it looks like, by setting a data attribute in AJAX, I
was overwriting the CSRF token. I don't remember it working that way, but
now we use beforeSend to add the X-CSRF-Token header instead, which is nicer,
anyway. The issue might've been something else, but this worked :/
The CSS was also not showing the loading ellipsis properly. I think that's a
dev-only issue in how live assets are being served versus static assets, but
may as well add UTF-8 charset directives everywhere, anyway.
items#show has been very slow recently, and I think it's because there's a lot
of querying to be done. Another option would have been to attempt to
short-circuit Item#supported_species if not body specific, but that would
still leave us with 1s load times for body specific items, which is not
satisfactory. The short-circuiting might still be worth doing, but probably
not now.
I'm also not sure that this is actually the core performance problem, but
we'll see. It definitely helped on the dev server: items#show took about
200ms on item pages where everything but species images were cached, then
took about 30ms on subsequent loads. Looking like a good candidate.
This one was actually pretty darn clever - nobody's abused it, but
I was reading a blog post where someone described this type of
issue, I realized it was a brilliant attack, and then realized
DTI was vulnerable. Oops. Thanks for the solution, Jamie!
http://jamie-wong.com/2012/08/22/what-i-did-at-khan-academy/#XSS+Fix
Many forms on the site contain a hidden authenticity_token field,
unique to each visitory. If a user submits a request with an
invalid authenticity_token, Rails assumes that it's a CSRF attempt
and logs out the user. So, if we happen to cache those forms with
authenticity_token fields, all users who use that form will have
the same authenticity_token (valid for only the first user who
saw the form, invalid for everyone else), and all requests made
through that form will log out the user. Bad news.
So, we stopped caching those forms. Yay!
Sharing pane works, everything is great for guests. Logged in
users are on the way, since right now Share Outfit re-saves
anonymously rather than showing sharing data for the existing
outfit.
