ngx_lua how to remove http request header

Question

There is a param named "RedirectURL" in http request header. I want to remove it in ngx_lua and then send this request to RedirectURL, here is some snippet in nginx.conf

location /apiproxytest {

           set_by_lua $redirectURL '
                    return ngx.req.get_headers()["RedirectURL"]
            ';

            header_filter_by_lua '
                     ngx.header["RedirectURL"] = nil;
            ';

            echo "1:" $redirectURL;

            set_by_lua $redirectURL2 '
                    return ngx.req.get_headers()["RedirectURL"]
            ';
            echo "2:" $redirectURL2;

            proxy_pass $redirectURL;
}

When I test it use

curl --header "RedirectURL:www.google.com" xx.xx.xx.xx:xx/apiproxytest

I get result:

1: www.google.com
2: www.google.com

I don't know where the wrong is. Who can help me figure it out? Thanks for any help!

fannheyward · Accepted Answer · 2015-05-25 10:22:55Z

6

ngx.req.clear_header

location /apiproxytest {
    set_by_lua $redirectURL '
        local url = ngx.req.get_headers()["RedirectURL"]
        ngx.req.clear_header("RedirectURL")

        return url
    ';

    proxy_pass $redirectURL;
}

answered May 25, 2015 at 10:22

fannheyward

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Comments

Alexander Altshuler · Accepted Answer · 2015-05-22 12:15:35Z

It is usual mistake. You think that nginx directives are executed in the same order as in config file. There are a lot phases of processing of nginx configuration files. Good, but long explanation: Nginx directive execution order

In their execution order the phases are post-read, server-rewrite, find-config, rewrite, post-rewrite, preaccess, access, post-access, try-files, content, and finally log.

set_by_lua - phase: rewrite
echo - phase: content
proxy_pass - phase: content
header_filter_by_lua - phase: output-header-filter

You may see unlisted phase - output-header-filter. Also I know about output-body-filter. These are special phases and implemented in different way then rewrite, contect etc phases. I cannot find a documentation for these phases. Any help are welcome! But obviously they cannot be early then content phase.

Your config's directives are executed in next order:

set_by_lua directives
echo and proxy_pass directives
header_filter_by_lua directives

So ngx.header["RedirectURL"] = nil really executed later and has no influence to your echo directives.

Chao Zhang · Accepted Answer · 2017-05-05 06:48:52Z

1

You can use the API ngx.req.clear_header(header) or ngx.req.set_header(header, nil), which is

answered May 5, 2017 at 6:48

Chao Zhang

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