Assaf Arkin wrote:
> By definition an entity bean has a life cycle extending beyond that of
> the EJB server through the persistence layer (RDBMS, OODBMS, etc), so if
> you use any EJB server that complies with the specs you get automatic
> failover of entity beans.
>
I don't agree. Suppose a client has a reference to (the remote interface of) an entity
bean.
Each time a method call will be made to this bean, the container where this bean is
deployed
will be contacted. Now suppose that this container crashes, for any reason. There are
several
possibilities for the client:
1. The next calls to the bean will fail with an exception. The client will thus try to
get the
reference again from the home object, but it will fail. The client will then try to
create
again an InitialContext, but it will fail.
2. The next calls to the bean will fail with an exception. The client will thus try to
get the
reference again from the home object, but it will fail. The client will then try to
create
again an InitialContext, and this will work : the client will be able to get a new home
reference which will be able to create the entity bean in another container.
3. The next calls to the bean will fail with an exception. The client will thus try to
get the
reference again from the home object, and it will work the home object is not tied to
a single
container and is smart enough to find the bean in another container
4. The next calls to the bean will work, because the bean reference is smart enough to
contact
a new container where the bean is deployed if the original one has crashed.
This last point is what I would call "automatic failover", and I don't think it's
trivial to
implement and that all vendors are able to support this.
Do I miss something? Any thought about this?
JB.
>
> Just pick the one with the coolest name.
>
> arkin
>
> Jean-Baptiste Nizet wrote:
> >
> > dan benanav wrote:
> >
> > > Do any vendors provide for clustering with automatic failover of entity
> > > beans? I know that WLS does not. How about Gemstone? If not is there
> > > a reason why it is not possible?
> > >
> >
> > Inprise Application Server supports it. See
> >
>http://www.borland.com/devsupport/appserver/faq/Availability_Scalability_Performance.html
> >
> > JB.
> >
> > >
> > > It seems to me that EJB servers should be capable of automatic failover
> > > of entity beans and without that it will be difficult to write a
> > > clustered based application.
> > >
> > > dan
> > >
> > > ===========================================================================
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> >
> > --
> > Jean-Baptiste Nizet
> > [EMAIL PROTECTED]
> >
> > R&D Engineer, S1 Belgium
> > Excelsiorlaan 87
> > B-1930 Zaventem
> > +32 2 714 45 42
> >
> > ===========================================================================
> > To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> > of the message "signoff EJB-INTEREST". For general help, send email to
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>
> --
> ----------------------------------------------------------------------
> Assaf Arkin www.exoffice.com
> CTO, Exoffice Technologies, Inc. www.exolab.org
>
> ===========================================================================
> To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
> of the message "signoff EJB-INTEREST". For general help, send email to
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--
Jean-Baptiste Nizet
[EMAIL PROTECTED]
R&D Engineer, S1 Belgium
Excelsiorlaan 87
B-1930 Zaventem
+32 2 714 45 42
===========================================================================
To unsubscribe, send email to [EMAIL PROTECTED] and include in the body
of the message "signoff EJB-INTEREST". For general help, send email to
[EMAIL PROTECTED] and include in the body of the message "help".
