Add user_id obtained asynchronously to the exported metrics

[IonitaCatalin]

Hello !

I am currently working on a instrumentation metrics and tracing instrumentation library for Nest.js using OpenTelemetry .

What I am trying to achieve as of now is having a set of decorators that would adnotate functions so that when the providers are injected in the importing module the function scope will be hijacked and a Meter callback would be wraped to that function execution like so.

const method = {
      [prototype.name]: function (...args: any[]) {
        if (prototype.constructor.name === 'AsyncFunction') {
          return prototype.apply(this, args).finally(() => {
            metric();
          });
        } else {
          try {
            return prototype.apply(this, args);
          } finally {
            metric();
          }
        }
      },
    }[prototype.name];

    MetadataUtil.transfer(prototype, method);
    MetadataUtil.apply(method, this.metadataActiveKey, 1);

    return method;

Where the metric argument of this function would be something like this:

() => {
      counter.add(1, this.getAttributes());
    };

My only problem is that once I instantiated a new MeterProvider and I am getting the Meter out of it, it becomes impossible to update the Resources to add for instance details about the generated metric such as the user_id which is impossible to get synchronously, you only get it in the context of a request.

Would it be possible to change the Resources of a MeterProvider at runtime?

[legendecas]

Resource is designed to be an immutable representation of the entity producing telemetry. For example, a process producing telemetry that is running in a container on Kubernetes has a Pod name, it is in a namespace and possibly is part of a Deployment which also has a name.

You should set user_id in the attributes instead.