Hi,
I am trying to get access to a custom response header, save it into a variable, and get rid of it so that it will not be proxied back to the client. That variable is then used in the access logs.
Unfortunately, the following doesn't seem to work:

server {
listen 142.133.151.129:8090 default;

##Intial values for calculated access log variables
set $cache_status "-";
set $destination_addr "-";

location / {
proxy_set_header X-Real-IP $remote_addr;
proxy_pass http://my_upstream_server;

proxy_http_version 1.1;

proxy_max_temp_file_size 0; #size of the temp file when response doesn't fit in buffer

#Setting access log variables
if ($sent_http_x_cache = "HIT") {
set $cache_status "HIT";
}
if ($sent_http_x_cache != "HIT") {
set $cache_status "MISS";
}
set $destination_addr $sent_http_x_destination;
# now get rid of these response header fields
set $sent_http_x_destination "";
set $sent_http_x_cache "";
}

I am getting empty values for $sent_http_x_destination and $sent_http_x_cache.

Here is the curl request and response:

[root@CL10-RH66-lmchaka ~]# curl -Ov --range "100-1000000" http://142.133.151.129:8090/ao3/vod/soccer/worldcup2014/final1
< HTTP/1.1 206 Partial Content
< Server: openresty/1.9.3.1
< Date: Tue, 16 Feb 2016 22:25:32 GMT
< Content-Type: application/octet-stream
< Content-Length: 999901
< Connection: keep-alive
< Accept-Ranges: bytes
< Age: 660
< ETag: "3833945841"
< Content-Range: bytes 100-1000000/94371840
< X-Cache: HIT
< X-Destination: 142.133.151.94
<

I would appreciate if someone can help and provide a determistic way to see the response header fields and store them into variables.

Thanks