listen backlog

Eric Wong normalperson at yhbt.net
Fri Dec 3 02:35:09 EST 2010


ghazel at gmail.com wrote:
> On Thu, Dec 2, 2010 at 6:39 PM, Eric Wong <normalperson at yhbt.net> wrote:
> > ghazel at gmail.com wrote:
> >> I found this thread
> >> http://rubyforge.org/pipermail/mongrel-unicorn/2009-September/000031.html
> >> after googling for the same error located in my nginx error log.
> >>
> >> Is there some way to discover the current queue length of the backlog?
> >> Increasing the maximum size to 2048 "worked" for me as well, but
> >> obviously clients sit in the queue for a long time. If I could monitor
> >> queue length I could get some idea of when I have insufficient unicorn
> >> workers before the delay gets very high or requests fail.
> >
> > If you're using Linux, you can use Raindrops[1] to interrogate
> > via inet_diag or parse /proc/net/{tcp,unix} yourself.
> >
> > You can run Raindrops separate/standalone script:
> > http://git.bogomips.org/cgit/raindrops.git/tree/examples/linux-tcp-listener-stats.rb
> >
> > Or use it as middleware (see webpage):
> > http://raindrops.bogomips.org/
> >
> > git clone git://git.bogomips.org/raindrops
> 
> Amazing! I had somehow never heard of it.

Yeah, I don't have much interest in marketing; that's what users are
for, but it's a chicken-and-egg problem :x

> I use a unix socket for unicorn (should I not?)

UNIX sockets are faster for nginx <-> Unicorn, but Raindrops is slower
dealing with them since Linux doesn't export UNIX sockets stats to
netlink the same way it does for TCP sockets.  So there's always a
tradeoff :x

> so I had to make a copy of
> linux-tcp-listener-stats.rb to support that. Now I'm able to get stats
> for my unicorn master
> 
> However, there seems to be some problem getting stats on TCP sockets:
> 
> $ ruby linux-tcp-listener-stats.rb 127.0.0.1:9000
>             address     active     queued
> linux-tcp-listener-stats.rb:42:in `tcp_listener_stats': Connection
> refused - sendmsg (Errno::ECONNREFUSED)
>         from linux-tcp-listener-stats.rb:42
> $ grep  0100007F:2328 /proc/net/tcp
>    1: 0100007F:2328 00000000:0000 0A 00000000:00000000 00:00000000
> 00000000   500        0 25307310 1 ffff880134471700 3000 0 0 2 -1
> 
> None of the TCP sockets I know to exist seem to work - they all fail
> with that error.

Odd, which kernel do you have?  You might want to "modprobe inet_diag"
if you're on an older kernel.  Or you can just comment-out the TCP
code and use the UNIX sockets code.

-- 
Eric Wong


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