Make Singleton/Registration explicit

[yordis]

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• [x] This only affects the JavaScript OpenTelemetry library
• [x] This may affect other libraries, but I would like to get opinions here first

Context

Hey there, I notice that some of the classes hide the fact that they register themselves as global objects, for example:

https://github.com/open-telemetry/opentelemetry-js/blob/c85fbe6682b9a8fd52e4b99bdbb079833b04e845/packages/opentelemetry-tracing/src/BasicTracerProvider.ts#L137

Such practices make sense once you know what is happening, but cause confusion to figure out why things are getting overwritten.

export const provider = new WebTracerProvider();

// Nothing says that `provider` will be registered globally since `register` itself take arguments.
// Am I registering context managers? Well, sort of, we are registering more than that.
provider.register({
  contextManager: new ZoneContextManager() 
});

Alternative could be,

export const provider = new WebTracerProvider({
  contextManager: new ZoneContextManager() 
});

// or even 

provider.AddContextManger(new ZoneContextManager())

// Notice that I removed arguments, so the concept of `register` is a bit, but still confusing
provider.register();

Also this part, https://github.com/open-telemetry/opentelemetry-js/blob/f077df3f14414f8587282bdf54dff703d137d4b1/packages/opentelemetry-instrumentation/src/autoLoader.ts#L38-L41

Proposal

Remove implicitness global registration from Providers/Any global object.

import { trace } from '@opentelemetry/api';
import { registerProvider } from '@opentelemetry/api';
import { WebTracerProvider } from '@opentelemetry/web';
export const provider = new WebTracerProvider();

trace.registerProvider(provider);

Or implicit dependencies in the instrumentations.

import { registerInstrumentations } from '@opentelemetry/instrumentation';
import { WebTracerProvider } from '@opentelemetry/web';
export const provider = new WebTracerProvider();

const something =    new MyInstrumentation({
       tracerProvider:  provider
      // meterProvier: ...
    })

something.setTracerProvider(provider);

registerInstrumentations({
  instrumentation: [
    something,
    new MyInstrumentation({
       tracerProvider:  provider
      // meterProvier: ...
    }),
  ],
});

Notes

I would like to understand the decision made since it is not clear to me looking at the existing code; and from the first-hand experience, I had to debug code in order to understand the hidden (and important) registrations and the dependencies between them.

[Dharin-shah]

+1 to this. Its not very obvious whats happening with the current design.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[MSNev]

We also need (should) address the implicit setting / usage of the global context, as this causes issues for multiple components that each want to have their own set of details.

[github-actions[bot]]

This issue is stale because it has been open 60 days with no activity. Remove stale label or comment or this will be closed in 14 days.

[yordis]

keep

[MSNev]

The sandbox is still in the process of getting setup -- it's realistically still a few months away before we will be starting to look to how we address this.