Adding args to a Request through InputFilter

Hi,

I would like to add args to a request on the fly thanks to an InputFilter.

It seems like the $f->r->args($new_args) doesn't record the new argument
inside the request.

For example :

Inside the filter :
sub handler{

my ($f, $bb, $mode, $block, $readbytes) = @_; # filter args # $mode,
$block, $readbytes are passed only for input filters

my $rv = $f->next->get_brigade($bb, $mode, $block, $readbytes);
return $rv unless $rv == APR::Const::SUCCESS;

print STDOUT "Perlfilter : Uri = ", $f->r->uri(),"\n";
print STDOUT $f->r->args(),"\n"; #No argument
$f->r->args("userId=10");
print STDOUT $f->r->args(),"\n"; #Returns the arg I passed
}

In a running perl script on my apache the $r->args() doesn't return
anything.

As I'm a newbie using mod_perl, a little help would be appreciated :)

Ivory
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Re: Adding args to a Request through InputFilter

On Tuesday 19 January 2010 17:11:03 Ivory wrote:
> I would like to add args to a request on the fly thanks to an InputFilter.
>
> It seems like the $f->r->args($new_args) doesn't record the new argument
> inside the request.
>
> For example :
>
> Inside the filter :
> sub handler{
>
> my ($f, $bb, $mode, $block, $readbytes) = @_; # filter args # $mode,
> $block, $readbytes are passed only for input filters
>
> my $rv = $f->next->get_brigade($bb, $mode, $block, $readbytes);
> return $rv unless $rv == APR::Const::SUCCESS;
>
> print STDOUT "Perlfilter : Uri = ", $f->r->uri(),"\n";
> print STDOUT $f->r->args(),"\n"; #No argument
> $f->r->args("userId=10");
> print STDOUT $f->r->args(),"\n"; #Returns the arg I passed
> }
>
> In a running perl script on my apache the $r->args() doesn't return
> anything.
>
> As I'm a newbie using mod_perl, a little help would be appreciated :)
>
What do you want to achieve?

In general I'd not recommend to change $r->args in a filter because a filter
is run when input is consumed and that is somewhat besides the normal program
flow.

Normally apache consumes input only in the response phase. A handler like the
default handler that has no use for input calls ap_discard_request_body() and
thus reads the input calls all input filters and puts the result in the bin. A
handler like mod_cgi processes the input but again, it consumes it only in the
response phase. CGI environment variables are set earlier. So changing $r-
>args in a filter cannot affect them.

Instead use a PerlFixupHandler or so.

PerlFixupHandler "sub {$_[0]->args(q{userId=10});0;}"

Torsten

Re: Adding args to a Request through InputFilter

Thanks for your explanation concerning the request processing (I think it
corresponds to the drawing I've seen
http://perl.apache.org/docs/2.0/user/handlers/http_cycle.gif here ) I
understand it much better now :)

The fact is that in order to add this arg to the request I need to call
several Web services, crypt and decrypt datas and access the cookies I've
previously stored in the clients navigator.

Is it also possible in this type of handler? (I've already tested all these
actions in an InputFilter and it works fine).

Thanks again.

Ivory

Torsten Foertsch wrote:
>
> On Tuesday 19 January 2010 17:11:03 Ivory wrote:
>> I would like to add args to a request on the fly thanks to an
>> InputFilter.
>>
>> It seems like the $f->r->args($new_args) doesn't record the new argument
>> inside the request.
>>
>> For example :
>>
>> Inside the filter :
>> sub handler{
>>
>> my ($f, $bb, $mode, $block, $readbytes) = @_; # filter args # $mode,
>> $block, $readbytes are passed only for input filters
>>
>> my $rv = $f->next->get_brigade($bb, $mode, $block, $readbytes);
>> return $rv unless $rv == APR::Const::SUCCESS;
>>
>> print STDOUT "Perlfilter : Uri = ", $f->r->uri(),"\n";
>> print STDOUT $f->r->args(),"\n"; #No argument
>> $f->r->args("userId=10");
>> print STDOUT $f->r->args(),"\n"; #Returns the arg I passed
>> }
>>
>> In a running perl script on my apache the $r->args() doesn't return
>> anything.
>>
>> As I'm a newbie using mod_perl, a little help would be appreciated :)
>>
> What do you want to achieve?
>
> In general I'd not recommend to change $r->args in a filter because a
> filter
> is run when input is consumed and that is somewhat besides the normal
> program
> flow.
>
> Normally apache consumes input only in the response phase. A handler like
> the
> default handler that has no use for input calls ap_discard_request_body()
> and
> thus reads the input calls all input filters and puts the result in the
> bin. A
> handler like mod_cgi processes the input but again, it consumes it only in
> the
> response phase. CGI environment variables are set earlier. So changing $r-
>>args in a filter cannot affect them.
>
> Instead use a PerlFixupHandler or so.
>
> PerlFixupHandler "sub {$_[0]->args(q{userId=10});0;}"
>
> Torsten
>
>

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Re: Adding args to a Request through InputFilter

On Wednesday 20 January 2010 11:40:43 Ivory wrote:
> The fact is that in order to add this arg to the request I need to call
> several Web services, crypt and decrypt datas and access the cookies I've
> previously stored in the clients navigator.
>
yes.

Cookies come in as HTTP headers. So $r->headers_in->{Cookie} can be used.

Torsten

Re: Adding args to a Request through InputFilter

Hi ,

I've manage to setup a PerlFixupHandler, and it works perfectly well for
adding / deleting headers and args.

But it seems like this process is pretty time-consuming... Any known issue
about that?

Ivory


Torsten Foertsch wrote:
>
> On Wednesday 20 January 2010 11:40:43 Ivory wrote:
>> The fact is that in order to add this arg to the request I need to call
>> several Web services, crypt and decrypt datas and access the cookies I've
>> previously stored in the clients navigator.
>>
> yes.
>
> Cookies come in as HTTP headers. So $r->headers_in->{Cookie} can be used.
>
> Torsten
>
>

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Re: Adding args to a Request through InputFilter

On Friday 22 January 2010 15:38:30 Ivory wrote:
> I've manage to setup a PerlFixupHandler, and it works perfectly well for
> adding / deleting headers and args.
>
> But it seems like this process is pretty time-consuming... Any known issue
> about that?
>
If "pretty time-consuming" means a few microseconds then yes, it may be
modperl.

If more, it's your code.

To figure out how much mod_perl costs try fetching a small static file with
and without this lines:

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

sub My::Handler::handler {0}


PerlFixupHandler My::Handler
-------------------------------------------

Use "ab -n 10000 -c 1 http://..." and compare the results.

Then add your fixup code and try again.

Torsten

Re: Adding args to a Request through InputFilter

You were right, after reviewing my code it works much better :)

Thanks again.

Ivory

Torsten Foertsch wrote:
>
> If "pretty time-consuming" means a few microseconds then yes, it may be
> modperl.
>
> If more, it's your code.
>
> To figure out how much mod_perl costs try fetching a small static file
> with
> and without this lines:
>
> -------------------------------------------
>
> sub My::Handler::handler {0}
>
>
> PerlFixupHandler My::Handler
> -------------------------------------------
>
> Use "ab -n 10000 -c 1 http://..." and compare the results.
>
> Then add your fixup code and try again.
>
> Torsten
>
>

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