inventory-service

A Python Flask service that demonstrates OpenTelemetry zero-code instrumentation. app.py contains no OpenTelemetry imports — all traces, metrics, and logs are injected at runtime by the opentelemetry-instrument CLI wrapper via environment variables.

How zero-code instrumentation works

The Dockerfile runs two extra steps after installing application dependencies:

# Installs the opentelemetry-instrument CLI
RUN pip install opentelemetry-distro opentelemetry-exporter-otlp

# Auto-discovers installed libraries and installs their instrumentors
RUN opentelemetry-bootstrap -a install

The container then starts with opentelemetry-instrument wrapping gunicorn:

opentelemetry-instrument gunicorn --bind 0.0.0.0:5000 --workers 1 app:app

All OTel configuration is provided through OTEL_* environment variables — no code changes required.

Key environment variables

Variable	Default	Purpose
`OTEL_SERVICE_NAME`	`inventory-service`	Service identity in all signals
`OTEL_EXPORTER_OTLP_ENDPOINT`	`$OTEL_GATEWAY_ENDPOINT`	OTel gateway address
`OTEL_EXPORTER_OTLP_PROTOCOL`	`http/protobuf`	Transport format
`OTEL_TRACES_EXPORTER`	`otlp`	Enable trace export
`OTEL_METRICS_EXPORTER`	`otlp`	Enable metrics export
`OTEL_LOGS_EXPORTER`	`otlp`	Enable log export
`OTEL_PYTHON_LOG_CORRELATION`	`true`	Inject `trace_id`/`span_id` into log records
`OTEL_METRIC_EXPORT_INTERVAL`	`5000`	Export metrics every 5 s
`OTEL_TRACES_SAMPLER`	`always_on`	Sample 100% of traces