Custom context manager not respected when span processors / exporters are configured via env vars

[plengauer]

What happened?

Steps to Reproduce

Configure env vars to any kind of trace exporter.
Use the NodeSDK and configure a custom context manager via the ctor.

Expected Result

custom context manager is used

Actual Result

custom context manager is not used

Additional Details

When setting a span processor or trace exporter via the NodeSDK ctor, this causes an internal TracerProvider config to be eagerly created. In this case, the context manager is copied over from the SDK config to the created TracerProvider config. Later, in the start call, this config is respected when registering the tracer provider by getting the context manager from the config object and passing it on to the register call.

When NOT setting a span processor or trace exporter, no config object is eagerly created. In this case, the register call does not check the config of the SDK (where the context manager would be) but passes on no context manager at all.

OpenTelemetry Setup Code

class EnvVarContextManager {
  inner;
  
  constructor(inner) {
    this.inner = inner;
  }

  enable() {
    return this;
  }

  disable() {
    return this;
  }

  active() {
    let context = this.inner.active();
    if (opentelemetry_api.ROOT_CONTEXT == context) {
      context = new opentelemetry_sdk.core.W3CTraceContextPropagator().extract(context, { traceparent: process.env.OTEL_TRACEPARENT }, opentelemetry_api.defaultTextMapGetter);
    }
    return context;
  }

  bind(...args) {
    return this.inner.bind(...args);
  }

  with(...args) {
    return this.inner.with(...args);
  }

}

let sdk = new opentelemetry_sdk.NodeSDK({
    contextManager: new EnvVarContextManager(new context_async_hooks.AsyncLocalStorageContextManager()),
    //spanProcessor: new BatchSpanProcessor(new OTLPTraceExporter()) // add this back in to fix the custom context manager
    instrumentations: [getNodeAutoInstrumentations({'@opentelemetry/instrumentation-fs': { enabled: false }})]
  });

sdk.start()

package.json

"@opentelemetry/resources": "1.25.0",
    "@opentelemetry/semantic-conventions": "1.25.0",
    "@opentelemetry/api": "1.9.0",
    "@opentelemetry/core": "1.25.0",
    "@opentelemetry/sdk-node": "0.52.0",
    "@opentelemetry/sdk-trace-base": "1.25.0",
    "@opentelemetry/exporter-trace-otlp-proto": "0.52.0",
    "@opentelemetry/auto-instrumentations-node": "0.47.0",
    "@opentelemetry/exporter-metrics-otlp-proto": "0.52.0",
    "opentelemetry-resource-detector-git": "0.30.0",
    "@opentelemetry/resource-detector-github": "0.28.2",
    "@opentelemetry/resource-detector-container": "0.3.10",
    "@opentelemetry/resource-detector-aws": "1.5.1",
    "@opentelemetry/resource-detector-gcp": "0.29.10",
    "@opentelemetry/resource-detector-alibaba-cloud": "0.28.10",

Relevant log output

No response

[pichlermarc]

Yep, that's a bug. Thanks for the detailed report @plengauer.
I opened a PR (#4781) to fix this.