using $upstream* variables inside map directive

[unoobee]

I tried using $upstream_http_content_length inside the map directive with
the "volatile" parameter to specify the proxy_cache behavior, but the map
still uses the default value.
Is there any way to set the proxy_cache behavior depending on
$upstream_http_content_length via the map directive?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,249880,289963#msg-289963