scaling unicorn

Eric Wong normalperson at
Tue Jun 22 00:53:46 EDT 2010

Jamie Wilkinson <jamie at> wrote:
> On Jun 21, 2010, at 5:16 PM, Eric Wong wrote:
> >> overloading the server or hitting memory bandwidth issues.  The
> >> backlog is at the somaxconn default of 128, I'm still not sure if
> >> we will bump that up or not.
> > 
> > The default backlog we try to specify is actually 1024 (same as
> > Mongrel).  But it's always a murky value anyways, as it's
> > kernel/sysctl-dependent.  With Unix domain sockets, some folks use
> > crazy values like 2048 to look better on synthetic benchmarks :)
> Somewhat related -- I've been meaning to discuss the finer points of
> backlog tuning.
> I've been experimenting with the multi-server socket+TCP megaunicorn
> configuration from your CDT:
> Which I think is what this sentence from TUNING is talking about?
> 	"Setting a very low value for the :backlog parameter in “listen”
> 	directives can allow failover to happen more quickly if your
> 	cluster is configured for it."



Thanks for sharing, and good to this is working well for you.

I'm still unlikely to have the chance to test this anywhere soon, but
maybe more folks can give it a try now that we've had one successful
report.   More reports (success or not) would definitely be good
to hear.

> BTW, this configuration needs a cool name!

Since you're the first person brave enough to try (or at least report
about it), you shall have the honor of naming it :)

Eric Wong

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