[erlang-questions] gen_tcp:connect taking 3 seconds under load

Bob Ippolito <>
Fri Apr 16 03:01:09 CEST 2010

Are you testing on Mac OS X? I think this is a bug in the Mac OS X
kernel. I've seen behavior like this before only on Mac OS X and it's
reproducible with other environments, not just Erlang.

On Thu, Apr 15, 2010 at 5:56 PM, Jacob Vorreuter
<> wrote:
> Hi,
> I'm load testing an Erlang proxy server that accepts incoming client connections and proxies data to backend server sockets.  Normally, the call to gen_tcp:connect to open the backend socket takes under 3 milliseconds.  However, under heavy load this call sometimes takes 3 seconds.  The strange thing is that it rarely takes any amount of time in the middle of that range.  It's either 3 milliseconds or 3000.  This is the call I'm making:
> gen_tcp:connect(Ip, Port, [binary, {packet, 0}]).
> Has anyone seen this behavior before?  I'm load testing with ab, making anywhere from 64 to 1000 concurrent requests.
> Thanks,
> Jake
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