Re: HttPrevayler

Thanks. This is helping a lot. :)

Three kinds os failures:

1) Garden-variety bugs, broken links, etc. In these cases the web app
will behave deterministically so we don't have to consider these as
failures for our purposes.

2) Non-deterministic OutOfMemory-style catastrophical failures of the
web app. Every http request must be sent to the web app with a
sequence number as a parameter. The web app can refuse (reply with a
specific error) saying: "Sorry, you sent me request 45, I was
expecting request 42". HttPrevayler then starts re-sending requests
since 42. So, if the web app crashes (OOM or StackOverflow, for
example) and is rebooted, we are ok.

3) Network failures between proxy and web app. Solved the same as 2)
above, with the request sequence number.

Our only problem is failures which are both non-catastrophic AND
non-deterministic.

Klaus.


On Wed, Jun 10, 2009 at 3:00 PM, Sergey Didenko<[email protected]> wrote:
> So the web app can be written to be just in memory then.
> Or just to make occasional snapshots and load the last one on restart.
>
> Interesting idea. Though I can't understand right now how practical it is.
>
> What about failed requests? Does proxy just journal a request or does
> it wait to see if the web app fails?
>
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------------------------------------------------------------------------------
Crystal Reports - New Free Runtime and 30 Day Trial
Check out the new simplified licensing option that enables unlimited
royalty-free distribution of the report engine for externally facing 
server and web deployment.
http://p.sf.net/sfu/businessobjects
_______________________________________________
To unsubscribe go to the end of this page: http://lists.sourceforge.net/lists/listinfo/prevayler-discussion
_______________________________________________
"Databases in Memoriam" -- http://www.prevayler.org