Re: WHChangeNotification Question
Re: WHChangeNotification Question
- Subject: Re: WHChangeNotification Question
- From: Jean-François Veillette <email@hidden>
- Date: Fri, 31 Mar 2006 14:48:41 -0500
If you mean that this uncover a bug from Apple, then I doubt (but it
still could).
I simply think that the implementation doesn't take all the precautions
needed to lock the database cache in order apply changes in there.
This strategy worked at the time of WO4.x (the initial implementation
from David Newman), but this was long ago and WO changed since, and I
think that the locking strategy didn't adapt adequately.
- jfv
Le 06-03-31, à 14:39, James Cicenia a écrit :
Wow... confusion reigns... You would think this is one place where
Apple would have stepped in.
On Mar 31, 2006, at 1:23 PM, Jean-François Veillette wrote:
Beware that the wonder implementation distribute changes snapshot and
tries to apply them to the database cache.
Unfortunately, under load, you will realise that this is causing a
deadlock.
I haven't got to the point where I was able to debug this strategy.
Maybe you just need another lock somewhere in the eo stack to prevent
the dead lock, I do not know at that point. Maybe someone can look
at this.
Anyway, I started with wonder's code and used a different strategy
that I had seen already and was talked numerously here on the mailing
list, which is to publish globalID of changed eo (and not diffs), and
simply invalidate eos based on those globalIDs at the subscriber's
end.
We didn't have any locking problem since !
- jfv
Le 06-03-31, à 14:09, Ken Anderson a écrit :
No, not really. I personally really like how lightweight
WHChangeNotification is. I'm using a modified version of it because
I already have a pub/sub system that my apps are participating in.
It really depends on your Wonder threshold :)
Ken
On Mar 31, 2006, at 2:02 PM, James Cicenia wrote:
Ok -
So you are saying that I *should* use the Wonder version instead?
If so, is it stand alone, or, do I need ERX my classes etc.?
- James
On Mar 31, 2006, at 12:56 PM, Ken Anderson wrote:
James,
You need to configure it to know what instances you have, and what
classes you want distributed.
I believe the version available uses direct connect, so you'll
have to make sure that it's enabled.
There have been some concerns about issues with the direct connect
transport mechanism... it's suggested that you use some other type
of transport like JMS. I also believe that project wonder has
something similar to WHChangeNotification that already uses JMS.
Ken
On Mar 31, 2006, at 12:28 PM, James Cicenia wrote:
Hello -
Now that we went multiple instances, we are having refresh
problems and since this is a multi-user type application our
customer are now complaining. Basically, changes in one instance
are not reflected in the other.
So, I perused the list and found WHChangeNotification as the
magic answer. I downloaded it, made it into a framework in
Eclipse, and imported it, set the configurations carefully, and
have uploaded it to dev for testing.
No change in behavior!
Is there a magic step I am missing?
Thanks
James Cicenia
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