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uav
Asked: 2020-08-05 11:05:00 +0800 CST

Nginx rewrite/return phase order

  • 772

I know there are Nginx phases. Why does the following snippet deliver the "200 Host: example.com" instead of forwarding to Google? What would be a generally valid workaround to evaluate Lua higher or before?

server
{
    listen 80;
    server_name example.com;

    location /
    {
        rewrite_by_lua_block
        {
            return ngx.redirect('https://www.google.com/', 303)
        }

        default_type text/plain;
        return 200 "Host: $host";
    }
}

Maybe this doesn't make sense at first sight, but I have an intelligent way to block/redirect certain calls in the Lua block (or in a Lua file included at this point). This module should work in general. With proxy_pass, alias etc. it works fine. Only with return 200 it does not work. Does anyone have an idea?

nginx openresty lua ngx-http-rewrite-module

2 Answers

  1. https://github.com/openresty/lua-nginx-module#rewrite_by_lua

    Note that this handler always runs after the standard ngx_http_rewrite_module.

    So return 200 always executes before rewrite_by_lua_block.

    In your case you should stick to rewrite_by_lua_block (didn't check)

    if condition then
    return ngx.redirect('https://www.google.com/', 303)
else
    ngx.print("Hello");
    return ngx.exit(ngx.HTTP_OK)
end
    • 1

  2. Credits to Alexey Ten.

    As an intermediate conclusion (until proven otherwise), instead of using Nginx code directly, I must implement return 200 in Lua.

            rewrite_by_lua_block {
            -- Will be executed. Can of course be combined with a condition.
            return ngx.redirect('https://www.google.com/', 303)
        }

        content_by_lua_block {
            ngx.header["Content-Type"] = "text/plain"
            ngx.print("Host: "..ngx.var.host)
            return ngx.exit(ngx.HTTP_OK)
        }

    This is not what I want, but I had asked for a workaround. If anyone has a better one, go ahead.

    • 0