Module development question - Variables

[Jan Algermissen]

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?

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

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.

Jan