Module development question - Variables

[Maxim Dounin]

Hello!

On Thu, Aug 15, 2013 at 03:40:59PM +0200, Jan Algermissen wrote:

> Hi,
> 
> been trying to understand variables for a couple of hours - but I jut don't get it.
> 
> Can anyone explain, 
> 
> 
> 1)  How and when the variable setter function is called?

Something like this in a configuration:

    set  $variable  "foo";

will result in v->set_handler() being called during the "set" 
directive evaluation.

> 2) Whether I should / can call it myelf to set the variable.

Usually no.

> Use Case:
> 
> I write an access phase filter that extracts a bunch of 
> information from the Authorization header (think OAuth-like: 
> clientId, user,  but maybe also debug info about cryptography 
> performance, token expiry, acess ricghts -you get the idea).
> 
> I would like to store these per request values in a variable to 
> use them in the access log module to log them. 
> 
> E.g.:
> 
> log_format gzip '$remote_addr - $remote_user $my_module_client, 
> $my_module_infoxy ...'
> 
> I think I understand what I have to do to create the variable 
> (create in preconfiguartin handler, provide setter function) 
> 
> But how is the setter called and how  do I access the value to 
> store in the variable?
> 
> Should I make the value a static bucket in the module data that 
> is written per request and then copied to the variable in the 
> variable setter???
> 
> Existing modules only help a little, as they mostly set 
> variables to values that are part of the request struct anyway - 
> which my values aren't.

In most cases, it's enough to store data in a module context and 
provide a get_handler for a variable to access data via the module 
context.

-- 
Maxim Dounin
http://nginx.org/en/donation.html