Thanks for the information, now I know what to look for in this regard.
-----Original Message-----
From: Dave Wolf [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, November 01, 2000 6:55 PM
To: [EMAIL PROTECTED]
Subject: Re: availability during redeployment of an EJB.
<vendor>
Sybase EAServer handles this by
1) If a client is actively using an object, stateful or stateless when a hot
refresh occurs that clients instance is left intact.
2) All instances in the pool are flushed and replaced with the new
implementation
The client receives no Exception. As Cedric puts it, we silently redirect
new calls to the new versions of the implementations. We consider this an
HA requirement. Who wants to fill yuoru client with tons of catch/retries
for when a refresh might happen. You need HA for both unplanned as well as
planned maintenance. As Cedris says, this is accomplished through the use
of ClassLoaders in Sybase EAServer as well. We also provide a mechanism to
conrtol which classes are loaded by which Classloader. In this way you can
control exactly what classes are refreshed when a refresh is requested.
This applies to EJB's, WAR's etc. Refreshes are allowed at the server,
Application or Component level.
</vendor>
Dave Wolf
Internet Applicastions Division
Sybase
> > Also, if one redeploys, say a stateless session bean, that has been
used,
> > then how does it get evicted from memory, without a JVM shutdown? Can
J2EE
> servers
> > redploy with clients accessing the EJB being re-deployed, or do you have
to
> kick out
> > the clients off the system when you redeploy (forget 24x7x365)?
>
> These are the real tricky issues and I don't think there is a standard way
of
> proceeding. Some elements of response:
>
> - clients holding stubs to remote objects should receive a
> NoSuchObjectException (being silently redirected to a new instance is
probably
> not the best idea, but a point can be made for that as well)
>
> - the real problem lies in in-flight transactions. You can choose to
rollback
> them all right away (the easy way) or wait for them to time out. It all
> depends how sophisticated you want your deployment to be
>
> There are also several possible scenarios to make the new homes available
to
> existing clients.
>
> --
> Cedric
>
>
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