On Apr 30, 2007, at 2:56 PM, Ashley M. Kirchner wrote:
Actually, the way the vendor programmed it, we upload anywhere
between 4-800 images, then when someone goes to view that page,
that's when it creates the thumbs on the fly. Now, we're requested
this process be changed so that the thumbnails are created in the
background after uploading, so that when someone goes to view them,
they're already created and just pulled from cache.
Funny how the vendor seemed to think that generating thumbnails
on the fly, all 800 of them, would take, according to them, 'a
fraction of second per image' - sure, when you have 3 images, but
not when you have 800 images.
Ugh, yeah, that's...true if they generate the thumbnail on the actual
hit for the thumbnail and they live in fantasy-land where only one
person is browsing the site and that person's web browser asks for
one image at a time. In reality-land, there will be multiple users
and multiple simultaneous requests/user, so more outstanding requests
than processors, so requests can get at best delayed an additional
queue_size*per_image_time/n_processors, and more likely slowed even
more than that due to thrashing. I could easily see hitting some
timeout for individual GET requests as well as one for the total page.
In your position after hearing that crap I'd tell them to keep the
new image set hidden from users until the thumbnails are generated,
to provide a progress bar to the uploader, maybe some indication of
pending images in the interface for other admins, and probably to
provide pagination to limit the images/page to a more reasonable
number. And if I'm feeling particularly unforgiving, to launch
n_processors low-priority processes/threads to do the work so that it
completes quickly if the server is idle yet doesn't penalize user
requests going on at the same time.
(I'm not nice to vendors who say stupid things.)
--
Scott Lamb <http://www.slamb.org/>
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