[ejabberd] some questions, threads, concurrent users

Mickael Remond mickael.remond at erlang-fr.org
Mon Sep 6 18:35:23 MSD 2004

Andrew Taylor wrote:
> I am not familiar with Erlang (but it sure seems neat), so I have a few 
> questions about ejabberd...
> 1) is there an OS thread for each jabber client ?

No. An Erlang virtual machine schedule its on process inside a single OS 
thread. For question 4: This is why the behaviour of an Erlang 
application is strictly the same on Windows and Linux for example.
This is also why Erlang thread are very light.

> 2) is there an Erlang PID for each jabber client ?

Yes. At least one.

> 3) does a PID equate to an OS thread ?

No. See my answer to 1.

> 4) is the thread answer different on windows/linux ?

No. See my answer to 1.

> 5) any input on the max concurrent users/sessions that a single ejabberd 
> can handle (say 2GB, 3Ghz machine)

I think it should be at least 4000 concurrent users/sessions. Could be 
more but this figure is highly dependendant of the activity intensity of 
each user/session.

I hope this helps.

Mickaël Rémond

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