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From Leszek Gawron <lgaw...@apache.org>
Subject Re: thought I had fixe it
Date Mon, 24 Oct 2011 17:42:22 GMT
On 2011-10-24 19:22, Paul Joseph wrote:
>
> I think you may have the solution--I am indeed putting in a very heavy
> weight object into the continuation.  Let me go through this code and
> get back to you with questions if I may.

I simply remember what used to kill my site and what made up my first 
commits as cocoon commiter :)

have fun

Please DO enable session-bound-continuations! You gain:
- all continuations simply "vanish" for an expired session
- there is no single continuations collection
- you will prevent very strange errors where there is still a 
continuation that you can invoke but there actually is no user session 
anymore. Been there, broke that ;)

Remember that even though you delete heavy object from flowscript your 
implementation is still not "memory nice". You need to generate 
VeryLargeObject, render it and then forget it. Imagine 10 users doing it 
at the same time - kills your server anyway.

There are two solutions:

  - some Result object which does not hold all data but actually is an 
open rowset wrapper. Your jx:template iterates the rowset. The data is 
fetched from db as you go. Remember to finalize your resources in a 
cleanup function.

  - custom generator that queries database directly and emits SAX events.


Both solutions let you generate results on almost ANY size. One more 
gotcha: if you generate large responses please mind that by default 
cocoon buffers the whole response before it's streamed to client (just 
in case an exception throws in the middle it can send a nice HTTP 500 
instead of data broken in the middle). This introduces a momory strain 
on the server and a significant response delay (data is not being sent 
to client until it's fully generated).

If you are willing to accept inferior error handling you can disable 
this buffering for memory intensive pipelines (outputBufferSize):

> 		<map:pipeline>
> 			<map:parameter name="outputBufferSize" value="0"/>
> 			<map:act type="set-header">
> 				<map:parameter name="Expires" value="-1"/>
> 				<map:parameter name="Cache-Control" value="no-cache"/>
> 				<map:parameter name="Pragma" value="no-cache"/>
> 			</map:act>
> 			<map:match pattern="view/*.jx">
> 				<map:generate type="jx" src="view/{1}.jx"/>
> 				<map:transform src="stylesheets/prefixes.xsl"/>
> 				<map:serialize type="xml"/>
> 			</map:match>
> 			<map:match pattern="text-view/*.jx">
> 				<map:generate type="jx" src="view/{1}.jx"/>
> 				<map:serialize type="text"/>
> 			</map:match>
> 			<map:match pattern="listCoupons.do">
> 				<map:generate type="coupons"/>
> 				<map:serialize type="xml"/>
> 			</map:match>
> 			<map:match pattern="*.do">
> 				<map:call function="{1}"/>
> 			</map:match>
> 		</map:pipeline>

	lg

-- 
Leszek Gawron                            http://lgawron.posterous.com

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