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Alessandro
Asked: 2018-12-14 00:22:55 +0800 CST

Nginx listen on any port but rewrite on 8080

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I have set up an nginx proxy with Openresty. The proxy takes up an HTTP SOAP POST request, modifies it by using a LUA script written within the root location ("/") of the HTTP server on port 8080, and sends it to a backend server for processing, which works correctly.

When the proxy relays the connection to the backend server, it creates a new connection, as per TCP specs, generating a new source port different from port 8080, where the backend server should respond.

Is there a way to intercept the response on nginx, so that it'll be able to intercept such response and modify it accordingly, with a LUA script?

Thanks for any insights you may be able to provide.

nginx

1 Answers

  1. Best Answer

    Here is the example based on my previous answer:

        location / {
        access_by_lua '
            ngx.req.read_body()
            local body = ngx.req.get_body_data()
            body = string.gsub(body, "_v4", "_v2")
            ngx.req.set_body_data(body)
            local header = ngx.req.get_headers()["Content-Type"]
            header = string.gsub(header, "_v4", "_v2")
            ngx.req.set_header("Content-Type", header)
        ';
        proxy_pass http://192.168.1.3:1234;
        body_filter_by_lua '
            # getting response body
            local body = ngx.arg[1]
            # response body is in a "body" variable now
            # do some modifications with "body" variable
            # just an example: convert body to uppercase
            body = string.upper(body)
            # setting back modified response body
            ngx.arg[1] = body
        ';
    }

    If your response body is large enough, things can be more complicated because response processed by parts (by data chunks in nginx terminology).

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