[fpc-devel] [Solved] Strange behaviour with Synapse

[Geoffray Levasseur-Brandin]

Le dimanche 17 mars 2013 09:05:45 Ludo Brands a écrit :
> Also, get rid of all these synchronizes. When using multiple threads,
> you will be blocking your downloads too much. Every sock status change,
> you create a string for the GUI, synchronize to update the screen, call
> Application.Processmessages to make sure the GUI gets updated. That is a
> huge waste of resources and slows down downloads considerably. On top of
> that you have timers that also update the GUI.
> Turn this around. Have TDownloadDaemon do the complete download and
> nothing else. Put status in properties of TDownloadDaemon, using a
> critical section if you want to pass strings, and poll your download
> threads in the main thread to update the GUI. You have already a timer.
> Make it faster (fe. 200ms) and update your GUI from there. Nobody will
> see the difference. No more synchronize and Application.Processmessages
> anymore and your program flow becomes so much easier. Multi-threading is
> difficult and simplifying your program flow is key to getting it right.
> 
> I changed the project to GTK2 and got it running. It crashes not always
> at the same time but it is systematically in the synchronize in
> TDownloadDaemon.SockStatus and always when doing the HEAD. So that is a
> synchronize called inside a synchronize from the TDownloadListLoop. You
> should not call synchronize from the main loop. Worse,
> TDownloadDaemon.SockStatus calls Synchronize(FOnProgress) which calls
> TThread.Synchronize(self,AMethod). Self is TDownloadDaemon but since you
> call TDownloadDaemon.SockStatus here from the main thread, synchronize
> uses the wrong AThread. The first download it happens to work because
> there is no thread running when you do HEAD. The second time you aren't
> that lucky. In any case, this is an overly complex program flow and is
> simply asking for problems.
> 
> Ludo

Thank you for all the advices. I just removed TDownloadDeamon thread to merge 
it with TDownloader. And it works ! I still have to work on status/progress 
system which is a bit messy. If you are interested, I've just commited the 
changes in the svn repo.

Thank you again,
-- 
Geoffray Levasseur-Brandin <geoffray.levasseur-brandin at ac-toulouse.fr>
http://jeff.levasseur.tuxfamily.org/
GNU/PG : BF8BB8407CD26E89466CDA9BB1030FC59EF87775
Errare humanum est sed perseverare diabolicum aut cretinum.
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