--reload breaks OpenTelemetry auto-instrumentation (child subprocess doesn't inherit instrumentation)

[yonathan-wolloch-lendbuzz]

Summary

When using opentelemetry-instrument uvicorn app:app --reload, OpenTelemetry auto-instrumentation stops working and no traces are captured. Removing --reload restores tracing functionality.

The Problem

When --reload is enabled, uvicorn spawns a child subprocess to run the actual application. The opentelemetry-instrument CLI sets up instrumentation in the parent (reloader) process, but this instrumentation is not inherited by the child subprocess where the application actually runs.

Parent Process (reloader)          Child Process (app)
┌─────────────────────────┐        ┌─────────────────────────┐
│ opentelemetry-instrument│        │                         │
│ sets up instrumentation │   →    │ uvicorn runs app HERE   │
│ HERE                    │ spawn  │ NO instrumentation      │
└─────────────────────────┘        └─────────────────────────┘

Steps to Reproduce

# With --reload: NO traces captured
OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317" \
opentelemetry-instrument uvicorn app:app --reload --host 0.0.0.0 --port 8000

# Without --reload: traces ARE captured
OTEL_EXPORTER_OTLP_ENDPOINT="http://localhost:4317" \
opentelemetry-instrument uvicorn app:app --host 0.0.0.0 --port 8000

Environment

• Python: 3.14
• Uvicorn: latest
• OpenTelemetry packages: opentelemetry-distro, opentelemetry-instrumentation-fastapi, opentelemetry-exporter-otlp

Related Issues

• Flask Auto Instrumentation disappears on debug=True app reload - opentelemetry-python-contrib#546
• Flask auto-instrumentation w/ debug=True doesn't work - opentelemetry-python-contrib#477