On Friday, August 29, 2014 02:16:10 barry Chung wrote:
> On Tuesday, August 12, 2014 12:29:55 Alastair Scobie wrote:
> >> On 12/08/14 12:18, Kamil Dudka wrote:
> >> > On Tuesday, August 12, 2014 10:05:37 Alastair Scobie wrote:
> >> >> Whilst porting an in-house application, which uses libcurl, from RHEL6
> >> >> to RHEL7 we noticed that the time taken by libcurl to fetch a page had
> >> >> substantially increased. Even an attempt at fetching a non-existent
> >> >> page
> >> >> has increased from 10-20ms to around 150ms. This with just plain HTTP.
> >> >
> >> > What exactly do you mean by a non-existent page?
> >>
> >> A page for which you'll receive a 404. Ie. HTTP server address is
> >> correct, but actual page requested doesn't exist.
> >>
> >> >> Our first thought was that the API has changed in some subtle way and
> >> >> the fault must be in our code, but then we thought to try measuring
> >> >> the
> >> >> performance of the curl tool itself. To our surprise, we found the
> >> >> same
> >> >> performance disparity.
> >> >>
> >> >> Interestingly...
> >> >>
> >> >> * Adding the DNS address of the HTTP server to /etc/hosts (and
> >> >> specifying files,dns in /etc/nsswitch.conf) does not improve things
> >> >
> >> > Did you try to measure the time consumed by 'getent ahosts'?
> >>
> >> Small number of ms for both RHEL6 and RHEl7.
> >>
> >> >> * but, performance when using an IP address in the URL is fine (~
> >> >> 10-20ms) for both RHEL6 and RHEL7
> >> >
> >> > I was not able to reproduce this behavior. Is it reproducible locally?
> >>
> >> Yip, on several machines. I can ship you an strace if you like?
> >
> >I would prefer a self-contained program that I can use to repeat the bug.
> >
> >> (Daniel's suggestion of disabling the threaded resolver has fixed the
> >> issue for us).
> >>
> >> Cheers, Alastair
> >
> >The problem is that either you will not receive security updates for
> >(lib)curl any more, or the threaded resolver will be re-enabled on the
> >next update. Kamil
>
> We are also hitting this while porting our software to RHEL7. Like Alastair
> mentioned, using IP address does not have the issue. wget also works fine.
>
> Kamil, you should be reproduce this by
> 1) bring up a RHEL7 minimal installation
> 2) install httpd or lighttpd
> 3) sudo tail -f /var/log/lighttpd/access.log
> 4a) while [ 1 ]; do curl http://localhost/badpage; done
> 4b) while [ 1 ]; do curl http://127.0.0.1/badpage; done
>
> There will be huge difference in the access count per second between 4a) and
> 4b).
>
> BTW, I uninstalled 7.29.0-19.el7 and installed 7.37.1-3.0.cf.rhel7 from
> http://curl.haxx.se/download.html but the problem still seems to exist.
>
> Thanks,
> Barry

Hi Barry,

I forgot to mention it here on the list, but I was finally able to reproduce
the bug and it is now tracked in Red Hat Bugzilla:

    https://bugzilla.redhat.com/1130239

The fix has been applied on Fedora 19:

    http://pkgs.fedoraproject.org/cgit/curl.git/commit/?id=4524a0eb

Kamil
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Received on 2014-08-29