In the interest of clearing out Resque, I'm just gonna remove a lot of our more complex caching stuff, and we can do a perf pass for things like big item list pages once everything's upgraded. (I'm hopeful that the upgrades themselves improve perf; and if not, that some improved sensibilities 10 years later can find simpler approaches.)
We used get_multi when preparing the proxies to decide which to
load from the database, but then sent multiple get requests to
Memcache to re-fetch the same data from that get_multi. Silly!
Use the data that's already stored on the proxy anyway.
Some lame benchmarking on my box, dev, cache classes, many items:
No proxies:
Fresh JSON: 175, 90, 90, 93, 82, 88, 158, 150, 85, 167 = 117.8
Cached JSON: (none)
Fresh HTML: 371, 327, 355, 328, 322, 346 = 341.5
Cached HTML: 173, 123, 175, 187, 171, 179 = 168
Proxies:
Fresh JSON: 175, 183, 269, 219, 195, 178 = 203.17
Cached JSON: 88, 70, 89, 162, 80, 77 = 94.3
Fresh HTML: 494, 381, 350, 334, 451, 372 = 397
Cached HTML: 176, 170, 104, 101, 111, 116 = 129.7
So, overhead is significant, but the gains when cached (and that should be
all the time, since we currently have 0 evictions) are definitely worth
it. Worth pushing, and probably putting some future effort into reducing
overhead.
On production (again, lame), items#index was consistently averaging
73-74ms when super healthy, and 82ms when pets#index was being louder
than usual. For reference is all. This will probably perform
significantly worse at first (in JSON, anyway, since HTML is already
mostly cached), so it might be worth briefly warming the cache after
pushing.
That is, once we get our list of IDs from the search engine, only
fetch records whose JSON we don't already have cached.
It's simpler here to use as_json, but it'd probably be even faster
if I figure out how to serve a plain JSON string from a Rails
controller. In the meantime, requests of entirely cached items
are coming in at about 85ms on average on my box (dev, cache
classes, many items), about 10ms better than the last
iteration.
