Re: [apache-modules] Re: Internal redirect from an output filter (Apache2.x)

[Sumeet Singh <su...@openwave.com>]

William A. Rowe, Jr. wrote:

>Sumeet Singh wrote:
>
>  
>
>>>  I was wondering if invoking an internal-redirect from within an output filter is legal. I need to do that from my output filter but want to make sure that it conforms to apache2.0 API before I go ahead and design/code it.
>>>      
>>>
>
>I presume this is not safe, but is tolerated by die because we will mop up all
>of the resources very soon thereafter.  Note that it is only successful if the
>headers had not been set up in an earlier call to pass brigade that made it
>to the protocol stack.  I would look at the log results carefully and trace the
>request to ensure you are satisfied with the processing.
>
>It is certainly not recommended, that does not mean it's not possible.
>
>Bill  
>
>  
>
Yes, I also find it unsafe. However, note that some standard modules do 
that too. For example mod_include runs sub-requests from within its 
output filters. In my opinion this shouldn't be allowed, because with 
the wrong configuration a web-admin could cause the server to go into 
recursion. But since mod_include is a standard module, I guess what it 
does is considered legal.

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Re: [apache-modules] Re: Internal redirect from an output filter (Apache2.x)

[Sumeet Singh <su...@openwave.com>]

André Malo wrote:

>* Sumeet Singh <su...@openwave.com> wrote:
>
>[internal redirects in output filters]
>
>  
>
>>Yes, I also find it unsafe. However, note that some standard modules do 
>>that too. For example mod_include runs sub-requests from within its 
>>output filters. In my opinion this shouldn't be allowed, because with 
>>the wrong configuration a web-admin could cause the server to go into 
>>recursion. But since mod_include is a standard module, I guess what it 
>>does is considered legal.
>>    
>>
>
>Subrequests and internal redirects are entirely different things. A subrequest
>can be done from almost everywhere and affects just the data flow (if at all).
>An internal redirect affects the current _control flow_.
>
>nd
>
>  
>
I understand how a sub-request is different from an internal-redirect. 
However, my point was that of recursion. If you have any light to shed 
on the original question I asked (that whether it is legal to invoke 
ap_internal_redirect from an output filter) I would really appreciate that.

-rgds,
ss
p.s.
And by the way, I don't agree that sub-requests are *entirely different* 
from internal-redirects. For example if you did a subrequest-uri-lookup 
followed by a ap_run_sub_req you would still end-up running all the 
stages (except post-read-request) and generating data and sending it 
down the output filter stack. Same thing is done by internal-redirect. 
There are subtle differences like the state of r->main/r->next/r->prev, 
filters inherited by the new request, running or not running of 
post_read_request and quick-handler stages, but finally both are 
recursions. And both the above generate data going down the output 
filter stack. After calling ap_internal_redirect you are supposed return 
immediately with a OK/DONE, but what if you didn't - then you would 
essentially be doing what people do with subrequests.

If you wish to continue this discussion, please start a separate thread.

Re: [apache-modules] Re: Internal redirect from an output filter (Apache2.x)

[André Malo <nd...@perlig.de>]

* Sumeet Singh <su...@openwave.com> wrote:

[internal redirects in output filters]

> Yes, I also find it unsafe. However, note that some standard modules do 
> that too. For example mod_include runs sub-requests from within its 
> output filters. In my opinion this shouldn't be allowed, because with 
> the wrong configuration a web-admin could cause the server to go into 
> recursion. But since mod_include is a standard module, I guess what it 
> does is considered legal.

Subrequests and internal redirects are entirely different things. A subrequest
can be done from almost everywhere and affects just the data flow (if at all).
An internal redirect affects the current _control flow_.

nd