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
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Received on 2014-08-29