[Interest] Does QNetworkAccessManager support HTTP persistent connections? (keep-alive)
giuseppe.dangelo at kdab.com
Sat Jul 28 00:28:07 CEST 2018
On 26/07/18 17:01, Sze Howe Koh wrote:
> To clarify: Did the server respond to your GET with "Connection:
> keep-alive" instead of "Connection: close", when you downloaded a
> metadata file (*meta.7z)?
> I sent requests from 3 different programs with different user-agents
> (plus 1 request from a VM). All of them got "Connection: close" from
> the server.
It's clearly a server-side configuration problem.
Personal guess: I've just issues a GET for the URL you pasted above, got
this reply in Firefox:
> HTTP/1.1 200 OK
> Date: Fri, 27 Jul 2018 22:12:14 GMT
> Server: Apache/2.2.15 (CentOS)
> X-Prefix: 188.8.131.52/12
> X-AS: 12322
> Last-Modified: Mon, 29 May 2017 20:00:54 GMT
> ETag: "2a011fd-7fb-550af2502e980"
> Accept-Ranges: bytes
> Content-Length: 2043
> Connection: close
> Content-Type: text/plain; charset=UTF-8
The key part is the server string: Apache 2.2.15 on CentOS. Which means
CentOS 6, which made me ring an alarm bell in my head.
Quick check, download
Extract the RPM, and there it is, in all of its glory, a KeepAlive Off
by default in Apache's master configuration file:
> $ grep -nr KeepAlive .
> ./etc/httpd/conf/httpd.conf:73:# KeepAlive: Whether or not to allow persistent connections (more than
> ./etc/httpd/conf/httpd.conf:76:KeepAlive Off
This is a CentOS 6 specific change, as Apache's 2.2.15 default
httpd.conf _obviously_ ships with KeepAlive On:
> httpd-2.2.15$ grep -nr KeepAlive
> docs/conf/extra/httpd-default.conf.in:16:KeepAlive On
Cargo cult sysadminning FTW!
(Luckily, it seems to have been removed in CentOS 7).
> Interestingly, all 3 requests from Windows got a RST from the server,
> but the request from my Linux VM didn't. (All of them got "Connection:
> close", however). Is this a clue, or a red herring?
Giuseppe D'Angelo | giuseppe.dangelo at kdab.com | Senior Software Engineer
KDAB (France) S.A.S., a KDAB Group company
Tel. France +33 (0)4 90 84 08 53, http://www.kdab.com
KDAB - The Qt, C++ and OpenGL Experts
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