feat: add 'opentelemetry-exporter-otlp-json-common' package

[herin049]

Description

Follow up to #4910 to progress towards adding support for OTLP JSON.

Fixes #1003

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

tox -e py314-test-opentelemetry-exporter-otlp-json-common

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[tammy-baylis-swi]

Thanks for this and the benchmarks! I like how it's laid out very similarly to the otlp-proto-common.

removal of ~200 lines of Windows getting-started and opentracing-shim jobs from test_0.yml

I believe they were moved to test_1.yml

[herin049]

Thanks for this and the benchmarks! I like how it's laid out very similarly to the otlp-proto-common.

removal of ~200 lines of Windows getting-started and opentracing-shim jobs from test_0.yml

I believe they were moved to test_1.yml

That was my goal, although I made a few alterations/simplifications.

[tammy-baylis-swi]

Lgtm, would be great if others from the discussion to have a look too.

[RahulGopathi]

Hi, excited to see this progressing! We have a use case where OTLP JSON would be really valuable.

We're building an observability pipeline where traces need to be both forwarded to a backend (Langfuse) and persisted to disk as OTLP JSON files for audit/replay purposes. The current opentelemetry-exporter-otlp-proto-http only supports protobuf serialization, so we ended up writing a workaround using MessageToJson:

  from google.protobuf.json_format import MessageToJson
  from opentelemetry.exporter.otlp.proto.common.trace_encoder import encode_spans
  from opentelemetry.exporter.otlp.proto.http.trace_exporter import OTLPSpanExporter
  from opentelemetry.sdk.trace.export import SpanExportResult


  class OTLPJsonSpanExporter(OTLPSpanExporter):
      """OTLPSpanExporter that sends OTLP JSON instead of protobuf."""

      def export(self, spans):
          try:
              encoded = encode_spans(spans)
              serialized = MessageToJson(encoded, preserving_proto_field_name=True)
              self._session.headers["Content-Type"] = "application/json"
              return self._export(serialized.encode("utf-8"))
          except Exception:
              return SpanExportResult.FAILURE

This works but depends on internal APIs (encode_spans, _export). Having an official otlp-json-common package would give us a stable, supported way to produce spec-compliant OTLP JSON, both for HTTP export and file persistence.

Would love to see this merged. Happy to help test!

[pmcollins]

Thanks for doing this. LGTM overall, just a concern about raising exceptions.

[pmcollins]

Looks like this exception is not handled in this PR, but I suppose it could be handled by the caller in a subsequent one (we don't want the SDK to throw an unhandled exception). In any case, even if it were handled I'm not sure we want to fail the encoding call chain on a bad value. May be a better to log and keep going -- convert as much as possible to JSON and log any weird data that had to be skipped rather than skipping the entire message.

[pmcollins]

Ditto about raising an exception here.

[pmcollins]

nit: should this be 4 - Beta?