Re: FW: Application Clustering
Re: FW: Application Clustering
- Subject: Re: FW: Application Clustering
- From: Marek Wawrzyczny <email@hidden>
- Date: Thu, 13 Nov 2003 15:03:29 +1100
That's true if by 'session failover' you mean the ability to restore
past pages. I would be more interested in the ability to preserve any
EO's the user has created or modified during the session. Should an
instance fail, the user could then log back (or be transfered) into
another instance of the application and resume work.
On Thursday, Nov 13, 2003, at 04:59 Australia/Sydney,
email@hidden wrote:
<--- 8< original post trimmed >8 --->
The important fact here is that a component-action URL only has meaning
in the context of a
certain session, with an intact page cache. For instance, if the
[contextID] in the URL can not
be found in the session's page cache, that's when you get the
'backtracked too far'
exception---a component-action can not be evaluated unless the
[contextID] can be used to
restore a page from the session page cache. Without this, a
component-action URL is
meaningless, there's no way to know what it's supposed to do, what
action
is supposed to be
invoked, what page is supposed to be returned.
Hope this helps explain why 'session failover' for a component-action
based URL will require
an intact page cache in the receiving instance/session. A Direct
Action
URL is not subject to
this----a Direct Action URL does not depend on a session page cache for
it's meaning (even
if a session is present, it's page cache is not inherently neccesary to
determine the meaning
of a DA URL). Alternately, you could try to put additional information
in every URL, perhaps
as key/values on the end, that would provide meaning about what page
should be returned
even in the absence of an intact page cache, and this additional
meaning
could theoretically
be used in a session-failover situation. This would be kind of
tricky,
but is probably possible
for a relatively simple application with limited
functionality----coming
up with a system like
this that would work for any possible application code in any possible
component-action
situation would probably be so impractical as to be ruled out.
--Jonathan
Marek Wawrzyczny
software engineer
-------------------------->
ish group pty ltd
7 Darghan St Glebe 2037 Australia
phone +61 2 9660 1400 fax +61 2 9660 7400
http www.ish.com.au | email email@hidden
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