Hello,
Using Nginx vars it's able to access to the response headers from proxied server with $upstream_http_[name] notation. But how I can access to them in Lua code? Unfortunately, I cannot use ngx.var.usptream_http_... because some of the header's names which I need contains dots.
The reason I need the headers of the upstream responses is because I find the source values in the Log phase, after some of them was dropped.

    Yep, that works. But, as I mentioned in the question, I can't rely on nginx usptream_http_ vars due to some headers contains dots in their names. Like X-Something.foo: bar

      😯 I've retried it once again, and it works via using name translation like
      X-Something.Foo-Bar => ngx.var["upstream_http_x_something.foo_bar"]

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