Throttle requests with limit_req rate based on header from response to auth subrequest

[jarstewa]

Hmm, I notice this from the map documentation: 

> Since variables are evaluated only when they are used, the mere
declaration even of a large number of “map” variables does not add any extra
costs to request processing.

Here is what I suspect: 

1) The limit_req directive is being processed before the auth subrequest
2) Therefore, when the limit_req is present, the mapped variables are empty
since the header from the auth request is not present.  But when limit_req
is removed, the mapped variables are evaluated by the access_log, which
happens after the auth subrequest has been made.

Can anyone kindly confirm or reject this theory? 

Thanks again,
Jared

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,281034,281057#msg-281057