fastapi-api-logger

Plug & play auto-logging middleware for FastAPI with async I/O, structured JSON logs, request tracing, loguru integration, and a built-in dashboard.

Features

• Zero-config middleware — add one line and all requests are logged
• Structured JSON logs — timestamp, method, endpoint, status, status_code, response_time_ms
• Correlation / Request ID — unique ID per request, forwarded from API gateways, injected into response headers
• Day-wise log files — logs/2026-03-25.log, logs/2026-03-26.log, ...
• Async & non-blocking — logging never slows your API (bounded queue + background writer)
• Status categorization — SUCCESS (2xx), REDIRECT (3xx), WARNING (4xx), ERROR (5xx)
• Error tracebacks — full traceback captured for 5xx errors
• Request/response body capture — opt-in, with automatic sensitive field masking
• Loguru integration — optionally pipe all logs through loguru with configurable levels
• Built-in dashboard — web UI at /logs to browse, filter, and search logs in real-time
• Configurable log rotation — auto-deletes log files older than N days (you choose how many)
• Pure ASGI — works with FastAPI, Starlette, or any ASGI framework

Quick Start

Install

pip install fastapi-api-logger

# With loguru support
pip install fastapi-api-logger[loguru]

# With everything
pip install fastapi-api-logger[all]

Basic Usage (2 lines)

from fastapi import FastAPI
from fastapi_logger import LoggingMiddleware

app = FastAPI()
app.add_middleware(LoggingMiddleware)

That's it! All requests are now logged to logs/YYYY-MM-DD.log with unique request IDs.

Full-Featured Usage

from fastapi import FastAPI
from fastapi_logger import LoggingMiddleware, LogConfig, create_dashboard_router

app = FastAPI()

config = LogConfig(
    log_dir="logs",
    excluded_paths=["/health", "/docs", "/openapi.json"],
    enable_request_body=True,
    enable_response_body=True,
    sensitive_fields={"password", "token", "secret"},

    # Request ID
    enable_request_id=True,
    request_id_header="X-Request-ID",

    # Loguru
    enable_loguru=True,

    # Dashboard
    enable_dashboard=True,
    dashboard_prefix="/logs",

    # Rotation — delete logs older than 7 days
    log_rotation_days=7,
)

app.add_middleware(LoggingMiddleware, config=config)

# Mount the dashboard (visit http://localhost:8000/logs)
app.mount("", create_dashboard_router(config))

Correlation / Request ID

Every request gets a unique ID (UUID4). This is essential for debugging in production.

$ curl -v http://localhost:8000/users/1
< x-request-id: a1b2c3d4e5f6...

How it works:

• If the client sends X-Request-ID header (e.g., from an API gateway), the middleware uses it
• Otherwise, a new UUID is generated
• The ID is added to the response headers AND the log entry
• Your endpoint can access it via request.scope["state"]["request_id"]

@app.get("/users/{user_id}")
async def get_user(user_id: int, request: Request):
    request_id = request.scope["state"]["request_id"]
    return {"id": user_id, "request_id": request_id}

Loguru Integration

Enable loguru to get beautiful colored terminal output alongside file logging:

config = LogConfig(
    enable_loguru=True,
    loguru_level_success="INFO",     # 2xx
    loguru_level_warning="WARNING",  # 4xx
    loguru_level_error="ERROR",      # 5xx
)

Output:

2026-03-25 14:30:00 | INFO     | [a1b2c3d4] GET /users/1 → 200 SUCCESS (42.1ms)
2026-03-25 14:30:01 | WARNING  | [b2c3d4e5] GET /users/0 → 404 WARNING (3.2ms)
2026-03-25 14:30:02 | ERROR    | [c3d4e5f6] GET /crash → 500 ERROR (1.1ms)

Install loguru: pip install fastapi-api-logger[loguru]

Dashboard

A built-in web UI to browse your logs — no React, no npm, just enable it:

config = LogConfig(enable_dashboard=True, dashboard_prefix="/logs")
app.mount("", create_dashboard_router(config))

Visit http://localhost:8000/logs to see:

• Real-time log entries (auto-refreshes every 5s)
• Stats cards: total, success, warning, error counts + avg response time
• Filters: by status, method, endpoint search, date picker
• Sorting: newest, oldest, or slowest first
• Color-coded response times: green (<100ms), yellow (<500ms), red (>500ms)
• Expandable tracebacks and request bodies

Configuration Reference

All Options

Field	Type	Default	Description
log_dir	str	"logs"	Directory for log files
log_format	"json" / "text"	"json"	Log output format
excluded_paths	list[str]	["/health", ...]	Glob patterns to skip
enable_request_body	bool	False	Capture request body
enable_response_body	bool	False	Capture response body
sensitive_fields	set[str]	{"password", ...}	Fields to mask as ***
max_body_size	int	10000	Max body bytes to capture
log_rotation_days	int	30	Auto-delete logs older than N days (0 = keep forever)
include_traceback	bool	True	Include traceback for 5xx errors
enable_request_id	bool	True	Generate unique request ID per request
request_id_header	str	"X-Request-ID"	Header name for request ID
inject_response_header	bool	True	Add request ID to response headers
enable_loguru	bool	False	Also emit logs through loguru
loguru_level_success	str	"INFO"	Loguru level for 2xx
loguru_level_warning	str	"WARNING"	Loguru level for 4xx
loguru_level_error	str	"ERROR"	Loguru level for 5xx
enable_dashboard	bool	False	Enable the /logs web UI
dashboard_prefix	str	"/logs"	URL prefix for dashboard routes
dashboard_page_size	int	100	Entries per page in dashboard

Log Format

{
    "timestamp": "2026-03-25T14:30:00.123456+00:00",
    "method": "POST",
    "endpoint": "/orders",
    "status": "SUCCESS",
    "status_code": 201,
    "response_time_ms": 85.23,
    "request_id": "a1b2c3d4e5f67890abcdef1234567890",
    "client_ip": "127.0.0.1",
    "request_body": "{\"item\": \"widget\", \"password\": \"***\"}",
    "response_body": "{\"id\": 42}"
}

Architecture

Request → LoggingMiddleware (pure ASGI)
           ├─ Generates/extracts Request ID
           ├─ Injects X-Request-ID response header
           ├─ Measures response time (perf_counter)
           ├─ Captures status code, method, path
           ├─ Optionally captures request/response body
           ├─ Masks sensitive fields
           └─ Enqueues log entry (non-blocking, O(1))
                    ↓
              asyncio.Queue (bounded, 10k max)
                    ↓
              AsyncLogWriter (background task)
              ├─ Day-wise file: logs/YYYY-MM-DD.log
              ├─ Auto-rotation: deletes old files
              └─ Optional: loguru sink

Development

git clone https://github.com/paresh/fastapi-api-logger.git
cd fastapi-api-logger
pip install -e ".[dev]"

# Run tests (51 tests)
pytest tests/ -v

# Run the demo app
uvicorn examples.demo_app:app --reload
# Visit http://localhost:8000/logs for the dashboard

Publishing to PyPI

# Install build tools
pip install build twine

# Build
python -m build

# Verify
twine check dist/*

# Upload to TestPyPI (testing)
twine upload --repository testpypi dist/*

# Upload to PyPI (production)
twine upload dist/*

Versioning

Update version in two places:

• pyproject.toml → version = "X.Y.Z"
• src/fastapi_logger/__init__.py → __version__ = "X.Y.Z"

License

MIT