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Subject Re: EI Pattern question
Date Thu, 03 Apr 2008 09:28:20 GMT
Channels only have a RAM overhead so its no biggie having loads.

The last image could be anything though - it could be a number of
entity messages.

If you are trying to make a kinda distributed entity cache then you
probably dont wanna stream the entire DB to a new subscriber :-) so
having a single topic for updates to an entity; then loading
individual entities on demand is maybe a more suitable approach
On 03/04/2008, bwtaylor <> wrote:
> What would be cool is if you could do last-image on a per-message-group
> basis
> within a common channel.
> This "last-image" mechanism seems useful only when the the channel names
> correspond 1-to-1 with the entity whose state you need to know. It seems
> this implicity requires that a client know what channels exist up front. In
> the stock quote analogy, the client has to learn of an IPO through some
> other mechanism to know what channel to go to.
> I have a similar problem to the original poster's problem, but in my
> situation the content of my message identifies the id of an entity and
> another part of the content provides that entity's new state. The client
> doesn't know what entities exist up front. The channel itself may be
> communicating entity lifecycle events including new entity creations. Or
> suppose in the stock quote example, that IPOs happen by simply publishing a
> ticker/price message for a previously unknown ticker to a "stock-quotes"
> channel.
> I've never thought about it before, but how does activemq scale regarding
> proliferation of channels? How wide can you go before you  say "too many".
> If the number of entities in question is small, you could dynamically route
> messages on the stock-quotes channel to price only messages on the
> stock-quote.ticker channel.  But at some point having a crapload of channels
> has to cause problems. Suppose I'm the eBay and I'm publishing
> auction_item/action_status events. I doubt I could have a channel per
> auction item.
> James.Strachan wrote:
> >
> > See Last Image Caching which uses non-persistent topic subscriptions
> > but allows you to provide the 'last image' first before any further
> > updates...
> >
> >
> --
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