[sdk-node] automatically configure logs exporter based on enviornment variables

[pichlermarc]

Currently, we don't auto-configure a LogRecordProcessor/exporter combination when using the @opentelemetry/sdk-node package.
Goal of this issue is to implement exporter selection for metrics based on this specification:

• https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#exporter-selection

For this issue to be considered done we need to implement the following behavior:

If no log record proccessor is configured by the user:

• use OTEL_LOGS_EXPORTER environment variable to determine an exporter and add it to the LoggerProvider that's created by NodeSDK
  • pair it up with a BatchLogRecordProcessor
  • see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#exporter-selection
• use the OTEL_EXPORTER_OTLP_LOGS_PROTOCOL to determine the OTLP exporter to use (http/json, http/protobuf, grpc)
  • see https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md#specify-protocol
• use the OTEL_EXPORTER_OTLP_PROTOCOL env var as a fallback to the above to determine the OTLP exporter to use (http/json, http/protobuf, grpc)
• fallback to using http/protobuf if none of the two protocol env vars are set

[mhennoch]

Can assign to me.

[pichlermarc]

It's yours 🙂

[evheniyt]

Hi guys, sorry for bothering you, but is it true that currently logs auto instrumentation is not supported for nodejs like we have it for python?

If yes, is PR #4740 implement this?

[trentm]

@evheniyt Recent versions of instrumentation packages for Bunyan, Winston, and Pino do support auto-instrumenting those libraries to support log sending via the Logs Bridge API (https://opentelemetry.io/docs/specs/otel/logs/bridge-api/). However, for that log sending to work, a global LoggerProvider needs to be setup to receive those log records from the instrumented libraries. This issue is about getting the OTel SDK for Node.js (a.k.a. NodeSDK) to automatically register a global LoggerProvider is a way similar to how it registers a default global TracerProvider for tracing.

[trentm]

to automatically register a global LoggerProvider

Currently, when using the NodeSDK, it will only register a global LoggerProvider if you pass in the logRecordProcessor config option. Something like:

const sdk = new NodeSDK({
  // ... other options
  logRecordProcessor: new BatchLogRecordProcessor(new OTLPLogExporter())
});
sdk.start();

(Aside: I notice that the logRecordProcessor option isn't even documented at https://github.com/open-telemetry/opentelemetry-js/blob/main/experimental/packages/opentelemetry-sdk-node/README.md#configuration)