Some tiles slow to load

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2011-12-09
2012-10-06
  • Illtud Daniel
    Illtud Daniel
    2011-12-09

    We're generally very happy with iipserver & the iipmooviewer combination, it's
    working well for us, but one thing is puzzling me - sometimes a proportion
    (about 1/4) of the tiles are very slow to load, in the order of 1s, while
    the other tiles are loading < 100ms.I'm attaching firebug traces for you to
    see just how much of a problem it is.

    I've looked at the iipserver log, but that thinks that the particular tile is
    being served up in the same kind of timescale as the others. We're using
    apache 2.2.15 with mod_fcgid but I can't see anything in that config that
    would be hindering us.

    Anybody any ideas?

    (1st screenshot, 4 tiles, 1 slow):

    (2ns screenshot, 12 tiles, 3 slow):

    Once the tiles have been viewed once, loading is fine, so once they're in a
    cache somewhere everything's OK (but we have 100s of thousands of images, so
    many millions of tiles, they won't all be cached!).

     
  • Ruven
    Ruven
    2011-12-11

    So the iipsrv log timings don't show anything slow? What about Apache? Do the
    timestamps correspond to the timings in firebug? It's also possible this is
    something linked to your version of Firefox. Do you still get these delays in
    Chrome? And you say that once in cache, everything is fast, but how about
    trying to first empty the cache and reloading. Is it always the same tiles
    that are slow or is it random?

     
  • Illtud Daniel
    Illtud Daniel
    2011-12-15

    Ruven, thanks for your reply, sorry I haven't been about to get back to you
    earlier. The iipsrv log seems to show all tiles being generated in the same
    ~40ms as all the others, so it's probably not an iipserver problem, but in
    case anybody else had experienced the same thing, I was asking here.

    I haven't gone back to correlate the firebug & apache logs, I'll do that next
    (it'll be next year now). Then I'll try emptying the cache.

    Chrome behaves the same, so I don't think it's a client-side thing, and all
    the requests get fired off at once, it's just the response that's slow, so
    it's not likely to be an iipmooviewer problem.

    If I can't make it go away, I'll try lighttpd!

     


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