Re: [jboss-as7-dev] Add Notification support to the domain management API
On 26 Feb 2013, at 12:09, Jeff Mesnil wrote:
Le 25 févr. 2013 à 17:47, Heiko Braun <hbraun(a)redhat.com> a écrit :
> Do notification types have different TTL's? (i.e. MOTD)
I don't think that a TTL makes sense for a notification.
A notification is just a description of an event that *already occurred*. The only
meaningful date you have is the timestamp of the notification (that is an approximation of
the time when the event that triggered the notification occurred).
Let's take the example of resources added/removed.
If you receive a notification RESOURCE_ADDED for the resource A with the timestamp T, the
only thing you know for sure is that the resource was added at that time.
But this does not mean that the resource still exists when you handle the notification if
it has been removed in the meantime. Even in that case, the notification is still exact
and you will eventually receive a RESOURCE_REMOVED notification later on in that case.
Receiving notifications trough polling or push notifications does not change that: you
only receive notifications after the event occurred and you can only react to the past.
Does that make sense?
Yes. I started writing some stuff about making unconsumed notifications being
aware of each other so if there for example was an unconsumed ADD followed by a REMOVE,
the REMOVE would cancel the ADD. This really didn't make sense so I stopped writing
:-) A listener might need to do something to handle both events so as long as an address
has listeners registered I think the notifications should always be sent.
--
Jeff Mesnil
JBoss, a division of Red Hat
http://jmesnil.net/
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Kabir Khan
Prinicipal Software Engineer
JBoss by Red Hat