title: Structured Logging
description: Configure structured JSON logging with tracing-subscriber for JustAPI — a high-performance FastAPI alternative built in Rust.
keywords: structured logging, JSON logging, tracing-subscriber, FastAPI alternative, Rust web framework

JustAPI uses tracing for structured logging, supporting both human-readable text and machine-parseable JSON formats.

Default Logging

By default, JustAPI logs to stdout in a human-readable format:

RUST_LOG=info python app.py

JSON Log Format

Enable JSON logging for production log aggregation:

from justapi.logging import init_json_logging

init_json_logging()

JSON output:

{"timestamp":"2026-07-24T15:00:00Z","level":"INFO","message":"Server started","addr":"127.0.0.1:8000"}
{"timestamp":"2026-07-24T15:00:01Z","level":"INFO","message":"Request completed","method":"GET","path":"/items/42","status":200,"duration_ms":1.2}

Log Levels

Set via RUST_LOG environment variable:

RUST_LOG=warn python app.py     # Less verbose
RUST_LOG=debug python app.py    # More verbose

Production Guidelines

• Set RUST_LOG=info in production
• Do not log request bodies (may contain PII/secrets)
• Use JSON format for log aggregation (ELK, Loki, Datadog, etc.)
• Configure log sampling for high-traffic endpoints

See Also

• Metrics & Monitoring — Prometheus metrics
• OpenTelemetry — Distributed tracing
• Health Checks — Health endpoints