Is it possible to avoid chunked transfer on lua nginx during body_filter_by_lua_block?

Question

Let's say we want to change a response from a upstream, what we can do is to use Lua+nginx on the body_filter_by_lua_block phase, here's a snippet of that.

  server {
    listen 8181;
    location /media {
        alias /media/;
    }
  }

  server {
    listen 8080;

    location /media {
        proxy_pass http://localhost:8181;

        # we need to keep this url since we're going to rewrite
        set_by_lua_block $original_uri { return ngx.var.uri }

        # when the Lua code may change the length of the response body
        header_filter_by_lua_block { ngx.header.content_length = nil }

        # removing (rewriting) the filters
        rewrite_by_lua_block {
          local uri = ngx.re.sub(ngx.var.uri, "^/media/(.*)/hls/(.*)$", "/media/hls/$2")
          ngx.req.set_uri(uri)
        }

        # applying the bandwidth min filter
        # but we can use the ngx.var.original_uri to build/select the filters
        body_filter_by_lua_block {
          local modified_manifest = filtering(ngx.arg[1])
          ngx.arg[1] = modified_manifest
          ngx.arg[2] = true
        }
    }

This works just fine! But the thing is, in this way the response will be using chunked transfer, and some clients can not deal with chunked response, do you know how can I overcome that?

Did you already try "chunked_transfer_encoding off" in your config? — Lorem ipsum, Sep 09 '20 at 13:52
yeah, it removes the chunked transfer encoding but it also don't set the content length. — Leandro Moreira, Sep 09 '20 at 15:06
I think this link is usefull for you to understand why content-length is missing now: https://serverfault.com/questions/482875/nginx-removes-content-length-header-for-chunked-content — Lorem ipsum, Sep 09 '20 at 15:39
thanks, this I know =( I was wondering if I can avoid this streaming since I know the whole response size — Leandro Moreira, Sep 09 '20 at 17:24

score 0 · Accepted Answer · answered Sep 11 '20 at 14:09

I solved this problem by issuing a sub request and fulfilling the content length header.

    location /mmedia {
         content_by_lua_block {
            local uri = ngx.re.sub(ngx.var.uri, "^/mmedia/(.*)/hls/(.*)$", "/media/$1/hls/$2")
            local res = ngx.location.capture(uri)
            if res then
              ngx.header.content_length = #res.body
              ngx.print(res.body)
            end
         }
    }

Is it possible to avoid chunked transfer on lua nginx during body_filter_by_lua_block?

1 Answers1