Re: WHChangeNotification Question
Re: WHChangeNotification Question
- Subject: Re: WHChangeNotification Question
- From: Chuck Hill <email@hidden>
- Date: Fri, 31 Mar 2006 11:49:21 -0800
I think this was originally a framework from David Neumann who worked
at Apple. So in a way... I will say that I have never used this
framework. I have always found ways to maintain data freshness using
the tools provided in EOF. I don't think that one way is always
better than the other. The EOF way may produce more DB reads that
are needed. The notification framework will pass a lot messages
around about data not relevant to an instance. Certainly, adding the
notification framework is the less effort way of handling this.
Chuck
On Mar 31, 2006, at 11:39 AM, James Cicenia wrote:
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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