Re: Using NotificationListener to send uncache events

[Daniel Florey]

James Mason schrieb:
Based on my reading of the NotificationListener source this is the
sequence that needs to happen (Client and server are both Slide servers
in this case):
1. Client creates a NotificationListener
 

Yes, you can specify the repository host/port and the local udp listener 
port in the constructor.

2. Client subscribes to server with a Subscriber and receives a
subsription id
3a. Client periodically POLLs server for update events for all
subscription ids
 

The interval for polling can be specified in constructor. If set to a 
very large interval, poll is more or disabled.

	AND
	3b. Server sends NOTIFY request with a list of subscription ids
to client when a resource is updated
	3c. Client POLLs server to get a list of update events for the
notified subscription ids
4. Server returns list of update events for the specified subscription
ids
5. Client calls notify() on the Subscriber registered for each received
update event
 

You should in the end be able to simple register a subscriber and get 
called when the method you are listening for occurs. You also get the 
event specific information set by the RemoteInformation interface on 
server side in a simple map.

6. The subscriber fires a UrisModifiedEvent that is handled elsewhere to
uncache the Uris.
 

My suggestion would be to use the event collection on server side and 
throw the UrisModifiedEvent on server side with all changed uris 
specified in the RemoteInformation way.
So you should lateron be able to register for the UrisModifiedEvent on 
client side and get notified when any Uris change on server side and get 
the Uris in the information map at once.

First off, does this sequence of event looks like I'm using
NotificationListener properly?
Second, I'm concerned about the possibility of subscriptions being
dropped if a server goes down. In this scenario if the server where to
restart and lose the subscription id the client would no longer be able
receive events. Is there support for persistent subscriptions on the
server or perhaps a way to notify the client that the subscription was
lost so it can resubscribe?
 

At the moment the only way is to use the subscription lifetime and renew 
the subscription periodically. I'll have a look at making subscription 
persistent as this really seems to be needed if we want reliable event 
based cluster support...
Regarfds,
Daniel

-James
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