[Icecast-dev] icecast relay server performance testing

Philipp Schafft lion at lion.leolix.org
Fri Jun 10 10:09:36 UTC 2016

Good noon,

On Fri, 2016-06-10 at 12:50 +0900, Zahar Popov wrote:
> Hello
> I'm trying to measure the performance of the icecast relay server on
> 64kbps streams.
> The server is running in AWS [...]. I'm using the icecast-kh fork.
>  [...]
> I'm able to go up to around 9K simultaneous connections to the server
> (from two machines). [...]

First: -kh is a independent fork. So I can hardly speak for it. This
answer is completely based on the (often wrong) assumption that in this
case behaves exactly like the official Icecast2 in any stable and
supported version.

> It doesn't matter if i run one or more instances of the relay server,
> the limit seems to be OS global so when one instance is running with
> 5K connections and the other instance is getting close to 4K
> connections they both start dropping connections.
> I assume that there is some other setting of the stack that i didn't
> configure so i was wondering if anybody was able to run a few dozens
> of thousands of connections on one server. 

This should give you the hint: It's not a problem of Icecast2 as it
doesn't depend on the processes.

Basically: AWS is well known for their broken TCP stack. There is no
reason to run Icecast2 on AWS. Just use a normal server and be fine.
What you see above is just AWS's maximum connection limit per instance
or something. (But there are more problems known with AWS's TCP stack
that affect real world deployments of Icecast2.)

Have a nice day!

 (Rah of PH2)
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