[Qt5-feedback] SWF, IPC, & QtService...

[andrew.stanley-jones at nokia.com]

This seems to have gone a slightly different direction.  SFW was done as part of the Mobility project, but is equally valid on desktop systems.

In 2011 SFW supports In process (plugins), out of process (IPC).  IPC has 3 different backends, dBus, Localsocket, and Client/Service (symbian).

Localsocket is the fall back method when a more system specific method can't be used.  On Linux localsocket uses Unix domain sockets is about twice the speed of dbus. SFW was always designed to be the control channel not the data channel so this wasn't a major issue.  In testing it's been a 2-3ms increase in round trip times.

Windows lacks a specific backend, so it falls back to using QLocalSocket.  It could use COM afaik, but at this time we just haven't the demand or man power to do this work.  It seems logical to do, just like using dBus on linux.

I missed one point in my first email, and this maybe important when considering a COM backend.  When doing IPC on Linux or Symbian the two processes maybe have different privilege levels.  So it's important to avoid allowing security problems to occur due to attacks on the IPC method.  

Cheers,

-Andrew

--
Andrew Stanley-Jones, Software Engineer
Nokia, Qt Development Frameworks
Level 1, 53 Brandl St,
Brisbane Technology Park, Eight Mile Plains, QLD, Australia, 4113 http://qt.nokia.com/


-----Original Message-----
From: qt5-feedback-bounces+andrew.stanley-jones=nokia.com at qt.nokia.com [mailto:qt5-feedback-bounces+andrew.stanley-jones=nokia.com at qt.nokia.com] On Behalf Of ext Peter Kümmel
Sent: Wednesday, 15 June 2011 6:18 AM
To: qt5-feedback at qt.nokia.com
Subject: Re: [Qt5-feedback] SWF, IPC, & QtService...

On 14.06.2011 21:52, BRM wrote:
> Starting a new thread so as not to hijack the other one...
>
>
> ----- Original Message ----
>
>> From: Peter Kümmel<syntheticpp at gmx.net>
>> On 14.06.2011 21:09, Thiago Macieira wrote:
>>> Em Tuesday, 14 de June de  2011, às 20:55:08, Peter Kümmel escreveu:
>>>> Reading "majority of use  cases" I wonder why it is not used by QtCreator?
>> Is
>>>> this only due to  the release of SFW after  starting QtCeator
>>>> development, are  are there also technical reasons to not use SFW in
>>>>   QtCreator?
>>>
>>> Why does Qt Creator need SFW for?
>>
>> In an  initial blog of SFW,
>>
>>        http://labs.qt.nokia.com/2009/05/26/qt-service-framework/
>>
>> I read "This  initial release focuses on in-process".
>> And QtCreator also has a  infrastructure to load and unload services,
>> they call it  "ExtensionSystem":
>>
>>       http://doc.qt.nokia.com/qtcreator-extending/extensionsystem.html
>>
>> It's  only in-process but at a first glace it looks that SFW
>> could also be used for  the job.
>>
>
> The blog notes that out-of-process IPC will eventually be supported.
> Has this been done? Or is it planned for Qt5?

Have you read this

     http://doc.qt.nokia.com/qtmobility/service-frameworks.html

DBus is supported which is slow (the initial post of the thread)
and local sockets (domain sockets?) which could be much faster than DBus.
But I never used SFW.

I also wonder why it is labeled as "QtMobility" the scope of SFW is not
only mobility.

Peter

>
> If the QtService replacement is to use SFW to communicate between controller and
> daemon - which from some of what I read on SFW may make it a very nice fit for
> doing so - then the out-of-process IPC would certainly be necessary.
>
> Also, how does Windows COM come into play on this? If a module like the
> QtService replacement were to use SFW on Windows and COM were the back-end to
> SFW then would two programs be able to use different versions of the
> QtService/SFW backend? Or would they conflict with each other? (E.g. different
> compilers)
>
> Just trying to understand how we might be able to use SFW for the back-end comms
> in the new QtService replacement - why reinvent the wheel if we don't have to?
>
> Thanks,
>
> Ben
>
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