Hi Cyril,

On Tue, Aug 13, 2019 at 11:38:23AM +0200, Cyril Bonté wrote:
> Hi Willy,
> 
> This morning, I found another case where haproxy 2.0 abnormally consumes the
> cpu. It occured on my laptop when my network was not setup yet.
> 
> I could find a simple reproducer :
>   listen test
>     mode http
>     bind :8888
>     server s1 10.0.0.1:8888
> 
> then, curl http://localhost:8888/
> 
> 10.0.0.1 is unreachable and the connection stays in SYN_SENT, but haproxy
> progressively raises to 100% CPU even after stopping curl.
> running a second curl will raise the CPU up to 200%, etc...

Excellent, I think you caught it! I can reproduce it here, except that
it doesn't last long, as soon as I get the socket error it's done. So
we indeed broke something in the connection setup.

> I think I'll have time to investigate tonight but maybe you'll find the
> issue and the fix before me ;)

Let's try at least :-)

> It looks to be very specific to the 2.0 branch, I can't reproduce it in 1.9
> and 2.1.

Great, that's useful. I suspect the fdcache removal in 2.1 helps a lot
here ;-)

Thanks!
Willy

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