Whiteboard metrics port

I just configured the new whiteboard: I cloned the GIT repository, created a systemd service unit, created a DNS CNAME for my jitsi server, created a new x509 certificate, created an nginx web site that listen in https on the new domain and proxy_pass the requests to the nodejs hosting the whiteboard.

Now, I changed the default (80) port for nodejs using the NODE_PORT variable in the systemd service unit, but nodejs also tries to use port 9090 for the metrics. Is there any env variable that I may use for having Prometheus use a user defined port instead of 9090?

The reason I want to change the port is that it is already in use by another Prometheus, the one ran by jvb.

Thank you,

Do you mean something like

PORT=9090 node build/index.js

Yes, this changes the port of the web server, while I need to change the Prometheus client port.
From the source code, it seems you may pass options to it:

file: ./node_modules/socket.io-prometheus-metrics/dist/index.js

    constructor(ioServer, options) {
        this.boundNamespaces = new Set();
        this.defaultOptions = {
            port: 9091,
            path: '/metrics',
            createServer: true,
            collectDefaultMetrics: false,
            checkForNewNamespaces: true
        this.options = Object.assign({}, this.defaultOptions, options);

Here it is, in src/index.ts:

// listens on host:9090/metrics
prometheus.metrics(io, {
    collectDefaultMetrics: true

So, a non default option is already passed, but it is hardcoded.