[webkit-qt] about concurrent http connection restriction

[Jocelyn Turcotte]

Hello,
comments below.

On Tue, 29 Nov 2011 14:21:27 +0800
ext 陈敏华 <chenmh at cn.fujitsu.com> wrote:

> Hello everyone，
> 
> I just want to figure out how Qtwebkit handle for concurrent http connections, and I have found some relevant code from file "ResourceRequestQt.cpp. The code is as follows, but I can't understand it well.
> 
> // Currently Qt allows three connections per host on symbian and six
> // for everyone else. The limit can be found in qhttpnetworkconnection.cpp.
> // To achieve the best result we want WebKit to schedule the jobs so we
> // are using the limit as found in Qt. To allow Qt to fill its queue
> // and prepare jobs we will schedule two more downloads.
> // Per TCP connection there is 1 current processed, 3 possibly pipelined
> // and 2 ready to re-fill the pipeline.
> unsigned initializeMaximumHTTPConnectionCountPerHost()
> {
> #ifdef Q_OS_SYMBIAN
>     return 3 * (1 + 3 + 2);
> #else
>     return 6 * (1 + 3 + 2);
> #endif
> }
> 
> My question is as follows:
> 1. Does the maximum number of concurrent http connection for each host equal to 36？
The name of this WebCore methods can be misleading, the roles of each is that WebCore sends requests to Qt, and Qt establish connections to send those requests. So in this case, there would be maximum 36 requests distributed on 6 parallel connections to each host. If more requests are pending, WebCore will keep them for itself instead of throwing all of them at Qt.

> 2. Is there any restriction for overall number of http connection that can be hold by Qtwebkit at any time？
I didn't verify but I think we don't, though the OS might have some limits of its own.

> 3. Http 1.1 has a concept called "persistent connection", does QtWebkit support this feature？ If so， what's the relationship between the number of http request& reponse that have been made and the number of tcp sockets established?
The 6 parallel connections per host held by QNetworkAccessManager are persistent connections, when a pending request is fed to Qt, any already opened connection will be used if available instead of establishing a new one.

> Does anybody can help me solve this problem? 
> Thank you very much.
Hope this helps.

Jocelyn