Combating nginx 499 HTTP responses during flash traffic scenario

Eric Wong normalperson at
Fri Nov 30 23:47:11 UTC 2012

Eric Wong <normalperson at> wrote:
> Lawrence Pit <lawrence.pit at> wrote:
> > A related question: is it possible to get insight in what's in the
> > unicorn queue and for how long requests have been queued there?


> Using SystemTap (or similar solutions), I think the same information may
> be retrieved without modifying the Ruby process.  I'm just starting my
> exploration of SystemTap, though...

With a little help from a SystemTap maintainer, I wrote a script
to get the TCP queue times easily.

The UNIX domain socket one is still pretty fragile (comments inline) but
appears to work:

If you're using an older SystemTap, you may need to swap cpu_clock_*(0)
with gettimeofday_*().

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