I'm trying to read the Content-Encoding in a header_filter_by_lua block. I test using chrome's developer tools while requesting an url which respond with Content-Encoding: gzip. I use these checks:
local test1 = ngx.var.http_content_encoding
local test2 = ngx.header.content_encoding
local test3 = ngx.resp.get_headers()["Content-Encoding"]
and all of them give empty/nil value. Getting User-Agent in same way is successful so what's the problem with Content-Encoding?
ngx.var.http_content_encoding - would return request's (not response's) header
API below work for read access in context of header_filter_by_lua_block and later phases:
ngx.header.content_encoding works for me always and is the right way.
If it doesn't work - check https://github.com/openresty/lua-nginx-module#lua_transform_underscores_in_response_headers
ngx.resp.get_headers()["Content-Encoding"] also work, but not efficient to obtain single header.
To get the value from request use following
ngx.req.get_headers()["content_encoding"]
