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From "Carsten Ziegeler" <cziege...@s-und-n.de>
Subject [RT] Forwarding of internal pipeline calls
Date Mon, 08 Mar 2004 11:11:29 GMT
While using internal cocoon redirects, I found out that there are
potential problems with error handling (it might be that we have
discusses this already...).

Now, if you do a:
<map:redirect-to uri="cocoon://something"/>

than this is an internal pipeline call (and not a new http request).
This has of course some advantages (e.g. performance etc), but
has imho the drawback that in this case, the error handling
of the calling pipeline is *always* used. This means if an error
occurs while processing the "something" pipeline, the error
handler of the pipeline containing the redirect-to is invoked.

Now, in general this might be a good solution for internal pipeline
calls when they are used in a map:generate etc., but it's imho
a little unusal for a redirect.

We had recently the discussion on this list, if we need a general
solution to specify which error handler is used for internal pipeline
calls. I discussed this a little bit with Vadim on IRC during our
first friday and he suggest to specify this not on the caller but
on the called pipeline. So the map:pipeline containing the
"something" pipeline specifies what to do. Regardless if this is
the better choice than specifying it in the uri ("cocoon:...."),
it's technically nearly impossible. When the internal pipeline
is called, everything happens outside the treehandler and there is
no real chance to get the error handler etc. (Of course we could
change something here and there and then it will work.)

So, I just tried the other way:
<map:redirect-to uri="cocoon://something?cocoon:forward=true"/>

The current implementation I have can only be used for redirects,
although it's fairly simple to extend it to be used in
map:generate etc. as well.

WDYT? Is this of general interest?

Carsten 

Carsten Ziegeler 
Open Source Group, S&N AG
http://www.osoco.net/weblogs/rael/


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