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From: Eric Wong <normalperson@yhbt.net>
To: unicorn list <mongrel-unicorn@rubyforge.org>
Subject: Re: Combating nginx 499 HTTP responses during flash traffic scenario
Date: Thu, 29 Nov 2012 21:30:17 +0000
Message-ID: <20121129213017.GA925@dcvr.yhbt.net> (raw)
In-Reply-To: <E7534814-055D-4216-A2FA-DD05009BBC25@gmail.com>

Lawrence Pit <lawrence.pit@gmail.com> wrote:
> >[2] http://mid.gmane.org/CAK4qKG32dGgNbzTzCb6NoH5hu_DrHMOFaFhk-6Xvy-T86++ukA@mail.gmail.com
> >I haven't heard back on results of our nasty/crazy solution, though.
> 
> fyi: I've been running that patch for a while in our staging
> environment. As far as I can tell it works. Though we haven't tested
> it with older browsers such as IE6 (we do not have that requirement)
> nor with all of the API clients we see (java, python, etc., we do
> have that requirement).
> 
> Hopefully we're bringing that patch into our production environment
> within the next couple of weeks, and then we should see results
> later that week.
> 
> Tom Burns wrote:
> >Unexpectedly the patch also helped us ward off a DoS attack where the
> >attackers were disconnecting immediately after making a request.
> 
> Awesome!
> 
> The only thing that worries me is that Eric calls this a
> "nasty/crazy solution". :p Not sure why. Seems to me it's a rather
> smart solution that perhaps in the future would deserve to be the
> default.

Until now, it was unproven.  AFAIK, no other app server does
anything similar.

Maybe other servers/protocols have similar things, I'd love to know.

> 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?

On Linux, tcpi_last_data_recv in the structure returned by TCP_INFO
tells you when the last packet was received on the socket, so it's an
accurate indication of queue time.  Raindrops provides an interface for
accessing it:

  http://raindrops.bogomips.org/Raindrops/LastDataRecv.html

I haven't heard much feedback about it, though.

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...

Raindrops::Watcher is less accurate/informative, but can run without
modifying the process.  I've used this heavily, but haven't
found anything interesting since I don't get enough traffic.

  http://raindrops.bogomips.org/Raindrops/Watcher.html
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  parent reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-29 17:44 Tom Burns
2012-10-29 18:45 ` Eric Wong
2012-10-29 19:27   ` Hongli Lai
2012-10-29 19:41     ` Eric Wong
2012-10-29 21:06       ` Hongli Lai
2012-10-29 21:53   ` Eric Wong
2012-10-29 22:21     ` Tom Burns
2012-10-30 20:40     ` Tom Burns
2012-10-30 21:37       ` Eric Wong
2012-11-02 17:59         ` Tom Burns
2012-11-02 19:38           ` Eric Wong
2012-11-03 22:45             ` Tom Burns
2012-11-05 11:48               ` Eric Wong
2012-11-06  3:16                 ` Tom Burns
2012-11-06 21:23                   ` Eric Wong
2012-11-29 15:52                     ` Tom Burns
2012-11-29 20:30                       ` Lawrence Pit
2012-11-29 20:57                         ` Tom Burns
2012-11-29 21:30                         ` Eric Wong [this message]
2012-11-30 23:47                           ` Eric Wong
2012-11-29 20:41                       ` Eric Wong
2012-12-04  3:00                         ` Eric Wong
2012-11-29 21:19                       ` Eric Wong
2012-11-29 21:55                         ` [RFC/PATCH] check_client_connection: document local-only requirement Eric Wong
2012-11-29 23:47                           ` Tom Burns

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