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From Christian Haul <>
Subject Re: caching database generated pages / eventcache block to core?
Date Tue, 14 Oct 2003 19:52:35 GMT
Geoff Howard wrote:
> Christian Haul wrote:
>> On 13.Oct.2003 -- 03:02 PM, Geoff Howard wrote:
>>> - Durable subscription handling.
>> I think we need "at least once" semantics to avoid delivering dirty
>> caches. I've seen durable connections mentioned in conjunction with
>> subscribers that are offline. Cocoon shutting down would invalidate
>> caches anyway (and other program state), so is this really needed?
> Cocoon persists caches if configured to use persistent store (and if 
> jetty is not used at least as configured in the bundled version).  So 
> between that and network loss and reconnection, I've always thought 
> durable subscriptions would turn out to be crucial.

Oh yes! I tend to forget these things :-| Sure, this requires persistent 

> Generally, I've thought the eventcache needs to be "fail fast" in the 
> sense that if it encounters a condition that reveals that any events may 
> have been missed the entire cache (or at least anything with Event based 
> validity) needs to be invalidated.


About your idead of sending content with the messages -- at least if we 
are talking about caches it is probably too difficult to use this data 
to update the cache. But maybe we could re-request the same request that 
filled the cache before? Or is that hashed into the cache key and can't 
be reconstructed? OTOH doing that pro-actively could cause additional 
load at high times... Not sure about this.

>> OK, I've put the sample in a new JMS block and created an action that
>> could send JMS messages. There's a JMSConnection (bad name) that holds
>> connection properties and instantiates a connection + session.
> Ok, I'll check this out.  When I went back to look at the JMS block on 
> my HDD it was much thinner than I remembered it.  I'm sure I'll be able 
> to factor anything it offerred in to what you've got now.

Don't hesitate to dump things as you see fit. I assume you know a lot 
more about practical JMS than I do :-) (haven't *really* used JMS before)


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