dynamicReverseProxy for Ocpp chargebox backend

Objective

I have thousend equipments (EVSE/Ocpp/Soap/ws) on internet, which are supervised by some backends. Each equipmement is affected to one backend. A backend can change the list of equipment it supervise. Each backend is on a distinct IP (same port(s) )

For simplicity in installation, each equipment is configured with an unique backend URL ( https or wss ).

Unfortunatly, the ID of the equipement is not in http-header : it is in POST body data : Soap Header for http, URI for websocket ( this are requirement of Ocpp standard, whe cannot change that ! )

So whe must dispose of a reverse-proxy, which can rerouting equipement request/connexion to his backend.

This seem do be a programmable reverse-proxy.

So here is a solution with minimum of developpement.

Solution

A) A NGINX revers-proxy, with module LUA ( nginx become programmable ). Use of OpenResty for dispose of a complete Nginx config.

B) Backend send to a script ( by ssh ) his IP and the list of equipement ID.

C) when each backend have send his list, /etc/hosts is updated, white entry like :

<IP backend1>   <ID equipmement1>
<IP backend1>   <ID equipmement10>
<IP backend2>   <ID equipmement2>
 . . . .  

D) basic DNS in Debian distribution can expose this list, for nginx usage.

E1) Http: Nginx find Id Equipment in the body of each request, and replace FDQN by the ID of the equipement, in the current URL.

E2) WS: Nginx find Id Equipment in the URI each request, and replace FDQN by the ID of the equipement, in the current URL.

F) Id equipement arre mappind to IP-backend, when Nginx incoke the local DND indicated.

That's it !

Sources provided

A nginx.conf

• ddns config
• http route with LUA code ( content_read_by_block )
• ws route, idem

Debian installation

debian_install.md

scripts

No sources provided, the lector can improvise :)