NodeSDK support for OTEL_TRACES_EXPORTER, ...

[francisdb]

Is your feature request related to a problem? Please describe.

To consolidate configuration for all our services we would like to configure the node sdk fully through the use of env vars like we do for the java/ruby sdk

see the related specs here:
https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/sdk-environment-variables.md#otlp-exporter
https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md

Describe the solution you'd like

One example would be the following

// import buildTraceExporterFromEnv from somewhere
// configure the exporters you want to allow somewhere?

const sdk = new opentelemetry.NodeSDK({
    resource: new Resource({
        [SemanticResourceAttributes.SERVICE_NAME]: 'myservice',
    }),
    traceExporter: buildTraceExporterFromEnv(),
    instrumentations: [getNodeAutoInstrumentations()]
})

that buildTraceExporterFromEnv could also be the default for traceExporter

In the code we register a number of exporters we want to support

OTEL_TRACES_EXPORTER=otlp
OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=http/protobuf
OTEL_EXPORTER_OTLP_TRACES_ENDPOINT="https://..../v1/traces"

Describe alternatives you've considered

We currently have to do handle the OTEL_TRACES_EXPORTER / OTEL_EXPORTER_OTLP_PROTOCOL to exporter selection manually.

Additional context

Current situation:

• if you don't set a traceExporter on the NodeSDK tracing will be disabled

• When using BasicTracerProvider the exporter is configured through OTEL_TRACES_EXPORTER as in the spec

  opentelemetry-js/packages/opentelemetry-sdk-trace-base/src/BasicTracerProvider.ts

  Lines 251 to 261 in 7870e95

  	protected _buildExporterFromEnv(): SpanExporter | undefined {
  	const exporterName = getEnv().OTEL_TRACES_EXPORTER;
  	if (exporterName === 'none') return;
  	const exporter = this._getSpanExporter(exporterName);
  	if (!exporter) {
  	diag.error(
  	`Exporter "${exporterName}" requested through environment variable is unavailable.`
  	);
  	}
  	return exporter;
  	}

[svetlanabrennan]

I'll like to work on this issue please.

[svetlanabrennan]

A few questions on OTEL_TRACES_EXPORTER:

1. This is the only place that I can find that uses OTEL_TRACES_EXPORTER but I don't see it setting up any exporters. From this pr, it looks like it was just the first step to allowing this feature someday. Is my understanding correct? @vmarchaud Since you worked on that pr, your feedback/clarification would be appreciated.

2. Adding OTEL_TRACES_EXPORTER was questioned in the past in various issues (go, js, spec) because adding the different exporters to an SDK as dependencies would make the SDK heavy. So:

   • Do we still want to add this feature? And should we add this feature to the auto instrumenting packages like the sdk-trace-node and/or the sdk-node?
   • If someone sets OTEL_TRACES_EXPORTER to otlp, but didn't set OTEL_EXPORTER_OTLP_TRACES_PROTOCOL what protocol should we use (http/json, http/proto or grpc)?

Thanks for any feedback.

[francisdb]

This is what we currently use but it's far from complete

function setupTraceExporter(): SpanExporter | undefined {
  const exporter = process.env.OTEL_TRACES_EXPORTER ?? 'none'
  switch (exporter) {
    case 'otlp': {
      const protocol =
        process.env.OTEL_EXPORTER_OTLP_TRACES_PROTOCOL ??
        process.env.OTEL_EXPORTER_OTLP_PROTOCOL ??
        'http/protobuf'
      switch (protocol) {
        case 'http/protobuf':
          return new ProtoTraceExporter()
        case 'grpc':
          return new OTLPTraceExporter()
        default:
          throw new Error(`Unsupported OpenTelemetry protocol ${protocol}`)
      }
    }
    case 'console':
      return new opentelemetry.tracing.ConsoleSpanExporter()
    case 'none':
      // we can't use pino here, otherwise it will not be instrumented
      console.log('Tracing disabled.')
      return undefined
    default:
      throw new Error(
        `OpenTelemetry OTEL_TRACES_EXPORTER invalid value: ${exporter}`,
      )
  }
}

[francisdb]

There is a section on the default protocol for otlp:
https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#specify-protocol

If no configuration is provided the default transport SHOULD be http/protobuf unless ...

[vmarchaud]

Is my understanding correct?

Yes, i originally implemented few exporters in the PR before removing them because the sdk size.

Do we still want to add this feature? And should we add this feature to the auto instrumenting packages like the sdk-trace-node and/or the sdk-node?

From our discussion at the time we agreed that we didn't want this into the sdk-trace-node since its the core sdk that we want to be as lightweight as possible. However i do think this feature has its place into the sdk-node package where we bundle common exporters so end user can easily use them.

If someone sets OTEL_TRACES_EXPORTER to otlp, but didn't set OTEL_EXPORTER_OTLP_TRACES_PROTOCOL what protocol should we use (http/json, http/proto or grpc)?

Doesn't the spec precise a default OTEL_EXPORTER_OTLP_TRACES_PROTOCOL ?

[svetlanabrennan]

Doesn't the spec precise a default OTEL_EXPORTER_OTLP_TRACES_PROTOCOL ?

Ah yes I see it now. @francisdb provided a link to it above - I must have missed. The default is http/protobuf.

[github-actions]

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[svetlanabrennan]

Still working on this