From: Jamie Wilkinson <jamie@tramchase.com>
To: unicorn list <mongrel-unicorn@rubyforge.org>
Subject: Re: scaling unicorn
Date: Mon, 21 Jun 2010 19:34:33 -0700 [thread overview]
Message-ID: <F596AC52-4CD1-4543-9B04-7A19762995DC@tramchase.com> (raw)
In-Reply-To: <20100622001632.GA10082@dcvr.yhbt.net>
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:
http://rubyforge.org/pipermail/mongrel-unicorn/2009-September/000033.html
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."
Our app can catch a batch of requests which will be slow (1-3s), and these can pool on one individual server in our load-balanced EC2 cluster -- exactly the case for the multi-server failover setup.
I've put this into production under a healthy load (5000+ RPM) and it appears to work really well! Produces very high requests/s rates at significantly higher concurrency than without, and serves zero 502 errors (part of the goal)
I currently I have the unix socket set to a backlog of 64, then failing over to a TCP listener using backlog 1024 (so that things are queued rather than 502'd)
I can imagine there might be a case for keeping the TCP backlog low as well & serving errors when overloaded, rather than getting caught in an unrecoverable back-queue tarpit
I'm currently failing-over to a dedicated "backup" instance, so that I could measure exactly how much traffic is being offloaded. This means my benchmarks w/o failover are 1 server, but with failover is actually 2 servers. We're reconfiguring to something more like the original diagram at which point I'll do some cluster-wide stress-tests & share data/scripts/process.
BTW, this configuration needs a cool name!
-jamie
http://jamiedubs.com
http://fffff.at
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next prev parent reply other threads:[~2010-06-22 2:43 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <AANLkTilv4e_DPDKy440xotrlE7ucFIFXs74uHyGrzCKL@mail.gmail.com>
2010-06-22 0:16 ` [Mongrel] scaling unicorn Eric Wong
2010-06-22 2:34 ` Jamie Wilkinson [this message]
2010-06-22 4:53 ` Eric Wong
2010-06-22 18:03 ` snacktime
2010-06-22 18:57 ` Jamie Wilkinson
2010-06-23 9:32 ` Eric Wong
2010-06-22 19:18 ` Jamie Wilkinson
2010-06-22 17:30 ` [Mongrel] " snacktime
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