nginx.conf for selenium-grid hub

nginx.conf

#user  nobody;
worker_processes  1;

#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;

#pid        logs/nginx.pid;

events {
    worker_connections  1024;
}

http {
    include       mime.types;
    default_type  application/octet-stream;

    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';

    #access_log  logs/access.log  main;

    sendfile        on;
    #tcp_nopush     on;

    #keepalive_timeout  0;
    keepalive_timeout  65;

    #gzip  on;

    upstream seleniumhub {
        server 10.2.80.7:4444;
        server 10.2.80.10:4444;
    }

    server {
        listen 80;

        location ~ /wd/hub/session$ {
            proxy_pass http://seleniumhub;
            set $response_body '';

            # Reset the response's content_length, so that Lua can generate a
            # body with a different length.
            header_filter_by_lua_block {
                ngx.header.content_length = nil
                --ngx.log(ngx.ERR, " header filter ngx.var.upstream_addr ", ngx.var.upstream_addr)
            }

            body_filter_by_lua_block {
                local resp_body = ngx.arg[1]
                ngx.ctx.buffered = (ngx.ctx.buffered or "") .. resp_body
                if ngx.arg[2] then  -- arg[2] is true if this is the last chunk
                    ngx.var.response_body = ngx.ctx.buffered
                else
                    ngx.arg[1] = nil
                    return
                end

                -- extract the ip in number format from upstream host
                local upstream_host = '127.0.0.1'
                if ngx.var.upstream_addr then
                    local ngx_re = require "ngx.re"
                    local addrs = ngx_re.split(ngx.var.upstream_addr, ",")
                    if #addrs > 0 then
                        --ngx.log(ngx.ERR, "multiple upstream: " .. ngx.var.upstream_addr)
                        upstream_host = addrs[#addrs]
                    else
                        --ngx.log(ngx.ERR, "single upstream")
                        upstream_host = addrs
                    end
                end

                local o1,o2,o3,o4 = upstream_host:match("(%d+)%.(%d+)%.(%d+)%.(%d+)") -- this will exclude :4444 automatically
                local num = 2^24*o1 + 2^16*o2 + 2^8*o3 + o4
                local ip = math.floor(num)
                ngx.log(ngx.ERR, "current_response " .. ngx.var.response_body)
                local current_session_id =     ngx.var.response_body:match('"sessionId":"(%w+)')
                local new_session_id = ip .. 'dddd' .. current_session_id
                local modified_response = ngx.var.response_body:gsub(current_session_id, new_session_id)
                ngx.log(ngx.ERR, "current_session_id " .. current_session_id .. "new id " .. new_session_id)

                ngx.arg[1] = modified_response
            }
        }

        location ~ /wd/hub/session/.+ {
            set $target_host '';
            set $target_uri '';
            access_by_lua_block {
                local url = ngx.var.request_uri
                ngx.log(ngx.ERR, "url " .. url)
                local session_id = url:match('/wd/hub/session/(%w+)')
                local upstream_host_ip_in_num, upstream_session_id = session_id:match('(%w+)dddd(%w+)')
                local o1 = math.floor(upstream_host_ip_in_num/(2^24))
                local rem = upstream_host_ip_in_num % (2^24)
                local o2 = math.floor(rem/(2^16))
                rem = rem % (2^16)
                local o3 = math.floor(rem/(2^8))
                rem = rem % (2^8)
                local o4 = math.floor(rem)

                local upstream_host_ip =  o1 .. '.' .. o2 .. '.' .. o3 .. '.' .. o4
                ngx.var.target_host = upstream_host_ip
                ngx.var.target_uri = url:gsub(session_id, upstream_session_id)
             }
            proxy_pass http://$target_host:4444$target_uri;
        }
    }

    # HTTPS server
    #
    #server {
    #    listen       443 ssl;
    #    server_name  localhost;

    #    ssl_certificate      cert.pem;
    #    ssl_certificate_key  cert.key;

    #    ssl_session_cache    shared:SSL:1m;
    #    ssl_session_timeout  5m;

    #    ssl_ciphers  HIGH:!aNULL:!MD5;
    #    ssl_prefer_server_ciphers  on;

    #    location / {
    #        root   html;
    #        index  index.html index.htm;
    #    }
    #}
    include servers/*;
}