Hi Tim,
I'd like to explore your premise a bit more. What is your definition of an
"ejb server"? (I'm assuming you mean an "instance" of an EJB container).
Are you assuming that there is only JVM per ejb server, and that is why you
need a "cluster", perhaps distributed across multiple machines, for
scalability?
<vendor>
A GemStone "instance" can involve an arbitrary number of load-balanced VMs,
spread across multiple machines if necessary. And GemStone can
automatically maintain entity bean state consistency between and within
these VMs (subject to transaction boundaries) by virtue of its unique
Persistent Cache Architecture (PCA). Note that GemStone can also leverage
PCA to maintain HttpSession state consistency between multiple servlet
engine VMs.
</vendor>
Randy Stafford
Senior Architect
GemStone Professional Services
> -----Original Message-----
> From: Tim Fox [SMTP:[EMAIL PROTECTED]]
> Sent: Wednesday, August 23, 2000 4:23 AM
> To: [EMAIL PROTECTED]
> Subject: Question on clustering and scalability
>
> I have a question on the maintaining of state consistency and
> scalability on ejb servers.
>
> If I have, say, two ejb servers working in a load-balanced arrangements.
>
> Both servers are serving the same ejb classes.
>
> Client A is editing the Customer entity bean relating to "John Smith" on
> server A.
> The Customer entity bean relating to "John Smith" is also cached in
> memory on server B after a previous update. (I am assuming ejb servers
> cache objects in memory)
>
> Client A commits his changes to the underlying database.
> How does ejb ensure that the in memory cached instance of "John Smith"
> on server B is updated to reflect the changes made by Client A?
> Does it fire off an "update" event to all the servers?
> If so, and we have n servers then I image we have a scalability problem
> of order n-1. (Ie the server has to notify every other server that the
> update has happened)/
>
> If it doesn't then how can I possibly use entity beans in a load
> balanced environment?
>
> TIA
>
> --
> Tim Fox (��o)
>
> Hyperlink interactive
> http://hyperlink.com
> email: [EMAIL PROTECTED]
> phone: +44 (0) 207 240 8121
>
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