Re: HttPrevayler

The web app must process one transaction request at a time anyway or
else determinism is lost.

So we are supposing there are no long-running transaction requests.

Klaus.




On Wed, Jun 10, 2009 at 6:02 PM, Sergey Didenko<[email protected]> wrote:
> If this proxy relies on the current Prevayler and waits for a request
> to finish then one long request can suspend all the others. It will be
> a bottleneck because of the single lock inside Prevayler.
>
> If it does not wait for a request to finish then how those failed
> requests are going to be handled?
>
> On Wed, Jun 10, 2009 at 10:07 PM, Klaus
> Wuestefeld<[email protected]> wrote:
>> 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?
>>>
>>> ------------------------------------------------------------------------------
>>> 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
>>>
>>
>> ------------------------------------------------------------------------------
>> 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
>>
>
> ------------------------------------------------------------------------------
> 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
>

------------------------------------------------------------------------------
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