On Fri, Jan 9, 2015 at 9:46 AM, Gilles Dubuc <gilles(a)wikimedia.org> wrote:
The bottom line is that the thumbnail prerendering
provided insignificant
performance gains for this set of sizes. Infrequently requested thumbnails
is the main problem, not the fact that they are rendered on the fly the
first time they are requested.
It seems like the only way to increase image serving performance in our
current setup is to increase the expiry value in Varnish and/or increase
Varnish capacity. Right now 17% of image requests in Media Viewer are
Varnish misses, and 99.5% of those are pulling an existing thumbnail from
Swift. Varnish misses are twice as slow as hits on average.
FWIW here's what swift sees for time to first byte on HTTP GET in which it
returned 200 (99% percentile and average)
https://graphite.wikimedia.org/render/?width=672&height=381&_salt=1…