feat: open telemetry traces setup

[nosahama]

About this change - What it does

We add open telemetry traces to schema-registry.

• more context related files are moved to the schema_registry module, this also affects the PR coverage:
  • src/karapace/schema_registry.py → src/schema_registry/registry.py
  • src/karapace/schema_reader.py → src/schema_registry/reader.py
  • src/schema_registry/schema_registry_apis.py → src/schema_registry/controller.py
• some minor changes to the DI wiring
• only the _health endpoint is traced, we can build up from here
  • we wire the functions called by the health endpoint so they show up in the health check traces as seen in the screenshot below
• with the DI wiring, it'd be easier to add traces to all parts of the system, but still a challenge never the less

Example traces from the /_health endpoint

API span data

Healthcheck endpoint handler span data

Note: the entries under Logs are not logs from the python logging module or any other configured logger, but these are OTel span events, OTel logs and metrics will be added in future iterations.

Now with KafkaSchemaReader.ready() traced, we can clearly see from the UI that MasterCoordinator.get_coordinator_status() calls KafkaSchemaReader.ready() which was also called somewhere at the beginning of the endpoint handler.

[github-actions]

Coverage report

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
src/karapace
config.py
offset_watcher.py					27-30
src/karapace/coordinator
master_coordinator.py					152-157
src/karapace/kafka
admin.py					191-194
src/schema_registry
__main__.py					8-10, 20-22, 27-28, 36-44, 63-65
container.py
controller.py
factory.py					18-20, 61
reader.py					377-380
registry.py
src/schema_registry/middlewares
__init__.py					10, 37
src/schema_registry/routers
compatibility.py					11
config.py					12-13
health.py					8-13, 40-50, 59-93
master_availability.py					12
mode.py					11
schemas.py					10
subjects.py					12-13
src/schema_registry/telemetry
__init__.py
container.py					16
middleware.py
setup.py
tracer.py
Project Total

This report was generated by python-coverage-comment-action

[nosahama]

87131a0 shows how to add tracing to KafkaAdminClient.describe_topics()