Document integration with OpenTelementry

[adubovik]

Document integration with OpenTelemetry:

1. OTEL_* env vars and what they control
2. What metrics and trace information are exposed

[zsxh1990]

I can help with this documentation. The telemetry implementation is well-structured — here's a quick analysis of what's already in place:

Current Implementation

Environment Variables (from types.py)

Variable	Purpose	Default
OTEL_LOGS_EXPORTER	Enable log export (set to otlp)	None
OTEL_TRACES_EXPORTER	Enable trace export (set to otlp)	None
OTEL_METRICS_EXPORTER	Enable metrics export (otlp and/or prometheus)	None
OTEL_EXPORTER_PROMETHEUS_PORT	Prometheus metrics port	9464
OTEL_PYTHON_LOG_CORRELATION	Inject trace context into logs	false

Architecture

FastAPI App
├── FastAPIInstrumentor (auto-instruments HTTP requests)
├── URLLibInstrumentor (auto-instruments outbound HTTP)
├── SystemMetricsInstrumentor (CPU, memory, etc.)
└── LoggingInstrumentor (log correlation with traces)

Exporters:
├── OTLPSpanExporter → traces
├── OTLPLogExporter → logs
├── OTLPMetricExporter → metrics (OTLP)
└── PrometheusMetricReader → metrics (Prometheus endpoint)

Quick Start Examples

Minimal setup (traces only):

export OTEL_TRACES_EXPORTER=otlp
export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317

Full observability stack:

export OTEL_LOGS_EXPORTER=otlp
export OTEL_TRACES_EXPORTER=otlp
export OTEL_METRICS_EXPORTER=otlp,prometheus
export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
export OTEL_PYTHON_LOG_CORRELATION=true
export OTEL_EXPORTER_PROMETHEUS_PORT=9464

Would a PR adding a docs/telemetry.md with these details be welcome?

[adubovik]

Todo:

1. Include in the doc, how to configure th JSON format:

OTEL_PYTHON_LOG_CORRELATION=true
OTEL_PYTHON_LOG_FORMAT='{"level": "%(levelname)s", "time": "%(asctime)s", "pid": %(process)d, "logger": "%(name)s", "trace_id": "%(otelTraceID)s", "span_id": "%(otelSpanID)s", "message": "%(message)s"}'
OTEL_LOGS_EXPORTER=otlp
OTEL_TRACES_EXPORTER=otlp

1.1. Consider introducing a dedicated LOG_FORMAT variable as in Quick Apps: https://github.com/epam/ai-dial-quickapps-backend/blob/f29c43e8246a9632f36c53585ca733c2c650277e/README.md#log-format-configuration