mod_perl - using input filters and bucket brigades to pass data to subrequests

walinsky has asked for the wisdom of the Perl Monks concerning the following question:

Dear monks,

in a given situation we get xml data POSTed to our server, much alike RPC calls (actually they're a number of http (webdav) requests).

A (mod_perl) Fixuphandler traps these requests, parses the xml, and (should) from there on issue all requests to our server.

It seemed quite logical to (dynamically) create a subrequest for each given request. We would dynamically add a input filter to each subrequest, create a bucket brigade there, and fill the bb with the desired data; set the correct request headers, and run the sub-request.

(Part of) the code in the input filter that should do the trick is:

$bb = APR::Brigade->new($c->pool, $c->bucket_alloc);
my $ba = $bb->bucket_alloc();
my $nb = APR::Bucket->new($ba, $data);
$bb->insert_tail($nb);
my $b = APR::Bucket::eos_create($ba);
$bb->insert_tail($b);
$r->headers_in->{'Content-Length'} = length ($data);
$f->fflush($bb);
[download]

For some reason, the sub-request never picks up the bucket brigade. Is there something I've overseen, or am I just trying to do the plain impossible ?

rgrds,

walinsky

Comment on mod_perl - using input filters and bucket brigades to pass data to subrequests Download Code

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Re: mod_perl - using input filters and bucket brigades to pass data to subrequests by perrin (Chancellor) on Mar 10, 2008 at 17:04 UTC
No offense, but you're making this way more difficult than it needs to be. Don't make subrequests unless you have a real reason for it, like needing to run some special auth handler that can't be called directly from perl. They have overhead and complicate things. You can easily set a specific handler or directly call some perl code without any need for subrequests. It's simpler and faster. The way to pass data between phases or requests is $r->pnotes(). You just put the data there and then grab it in the next phase or subrequest. If you are in a subrequest, you have to ask for the parent request's record and look there for it. I think that's just `$r->parent()` but that's off the top of my head and could be wrong.	[reply] [d/l]
Re^2: mod_perl - using input filters and bucket brigades to pass data to subrequests by walinsky (Scribe) on Mar 10, 2008 at 21:39 UTC
The main reason for making subrequests is that we're getting a bunch of WEBDAV requests bundled in the POSTed request. We don't want to handle those in perl, as mod_dav was built to do it. We are already using the $r->pnotes for passing the data from the handler to the input filter. An other option would be using LWP - but that seems quite stupid, as we would loose the whole request environment. A third option would be writing xs code for gluing perl to mod_dav. If one has that code handy already, I'd be more than interested in trying that way	[reply]
Re^3: mod_perl - using input filters and bucket brigades to pass data to subrequests by perrin (Chancellor) on Mar 11, 2008 at 05:38 UTC
Ok, you could use subrequests for that. I'd still check out CPAN's DAV modules though. If you think subrequests to mod_dav are the way to go, bring your question about filters over to the mod_perl mailing list.	[reply]