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<  Open Telecom Platform (OTP)  ~  YAWS/Erlang’s maximum number of simultaneous open ports?
kovacschris
Posted: Sun Jan 24, 2010 5:21 pm Reply with quote
Joined: 24 Jan 2010 Posts: 1
Does the erlang TCP/IP library have some limitations? I've done some searching but can't find any definitive answers.

I have set the ERL_MAX_PORTS environment variable to 12000 and configured Yaws to use unlimited connections.

I've written a simple client application that connects to an appmod I've written for Yaws and am testing the number of simultaneous connections by launch X number of clients all at the same time.

I find that when I get to about 100 clients, the Yaws server stops accepting more TCP connections with

Error in process with exit value: {{badmatch,{error,socket_closed_remotely}}
I know there must be a limit to the number of open simultaneous connections, but 100 seems really low. I've looked through all the yaws documentation and have removed any limit on connections.

This is on a 2.16Ghz Intel Core 2 Duo iMac running Snow Leopard.

A quick test on a Vista Machine shows that I get the same problems at about 300 connections.

Is my test unreasonable? I.e. is it silly to open 100+ connections simultaneously to test Yaws' concurrency?

I came across this thread about TCP throughput . Am I bumping up against the same problem?


Thanks.
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Michal Ptaszek
Posted: Tue Feb 02, 2010 1:51 pm Reply with quote
User Joined: 01 May 2008 Posts: 35 Location: Krakow
I guess it is because of the system's limit. Each operating system has the maximum number of simultaneously opened sockets.

If you want to check the number run
Code:
ulimit -n

on your Mac.

I am not an expert when it comes to the Mac Os. Under Linux you will have to change /etc/security/limits.conf file (nofile parameter).
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