fastapi-request-context 1.3.0

FastAPI middleware for request ID tracking, correlation IDs, and extensible request context with logging integration

fastapi-request-context

FastAPI middleware for request ID tracking, correlation IDs, and extensible request context with first-class logging integration.

Features

• Automatic request ID generation - Every request gets a unique ID
• Correlation ID support - Accept from header or generate for distributed tracing
• Response header injection - Automatically add X-Request-Id and X-Correlation-Id to responses
• Pluggable context backends - Use contextvars (default) or context-logging
• Custom context fields - Extend with your own fields via StrEnum
• Logging integration - JSON and human-readable formatters with automatic context injection
• Exception context - Context automatically added to exception args for debugging
• Validation utilities - Check that routes and dependencies are async
• Zero configuration - Works out of the box with sensible defaults
• Type-safe - Full type hints and mypy strict mode

Installation

# Basic installation
pip install fastapi-request-context

# With context-logging support
pip install fastapi-request-context[context-logging]

# With JSON formatter support
pip install fastapi-request-context[json-formatter]

# All optional dependencies
pip install fastapi-request-context[all]

Using uv:

uv add fastapi-request-context

Quick Start

from fastapi import FastAPI
from fastapi_request_context import RequestContextMiddleware

# Create your app
app = FastAPI()

# Keep reference to raw app if needed (e.g., for TaskIQ, testing)
raw_app = app

# Wrap with middleware
app = RequestContextMiddleware(app)

Every request now has:

• Unique request_id (always generated)
• correlation_id (from X-Correlation-Id header or generated)
• Both added to response headers
• Context available in all log records (including access logs!)

Usage

Access Context Values

from fastapi_request_context import get_context, get_full_context, StandardContextField


@app.get("/")
async def root():
    request_id = get_context(StandardContextField.REQUEST_ID)
    correlation_id = get_context(StandardContextField.CORRELATION_ID)

    # Or get everything
    all_context = get_full_context()

    return {"request_id": request_id}

Custom Context Fields

from enum import StrEnum
from fastapi_request_context import set_context, get_context


class MyContextField(StrEnum):
    USER_ID = "user_id"
    ORG_ID = "org_id"


async def get_current_user(token: str):
    user_id = decode_token(token)
    set_context(MyContextField.USER_ID, user_id)
    return user_id


@app.get("/me")
async def me(user_id: int = Depends(get_current_user)):
    # Context is available throughout the request
    return {"user_id": get_context(MyContextField.USER_ID)}

Configuration

from fastapi_request_context import RequestContextMiddleware, RequestContextConfig
from uuid import uuid4

config = RequestContextConfig(
    # Custom ID generators
    request_id_generator=lambda: str(uuid4()),
    correlation_id_generator=lambda: str(uuid4()),

    # Custom header names
    request_id_header="X-My-Request-Id",
    correlation_id_header="X-My-Correlation-Id",

    # Disable response headers
    add_response_headers=False,

    # Use context-logging adapter
    context_adapter="context_logging",

    # Only process HTTP (not WebSocket)
    scope_types={"http"},
)

app = RequestContextMiddleware(app, config=config)

Logging Integration

JSON Formatter (Production)

import logging
from fastapi_request_context.formatters import JsonContextFormatter

handler = logging.StreamHandler()
handler.setFormatter(JsonContextFormatter())
logging.basicConfig(handlers=[handler], level=logging.INFO)

# Logs automatically include context (nested under "context" key by default):
# {"message": "Processing", "level": "INFO", "context": {"request_id": "...", "user_id": 123}}

Simple Formatter (Human-Readable)

from fastapi_request_context import StandardContextField
from fastapi_request_context.formatters import SimpleContextFormatter

handler = logging.StreamHandler()
handler.setFormatter(SimpleContextFormatter(
    fmt="%(asctime)s %(levelname)s %(context)s %(message)s",
    shorten_fields={StandardContextField.REQUEST_ID},  # Show first 8 chars
    hidden_fields={StandardContextField.CORRELATION_ID},  # Hide completely
))
logging.basicConfig(handlers=[handler], level=logging.INFO)

# Output: 2025-01-15 10:30:00 INFO [request_id=3fa85f64… user_id=123] Processing

Access Logs Integration

Context is automatically available in all log records, including Uvicorn access logs when using context-logging adapter:

from fastapi_request_context import RequestContextMiddleware, RequestContextConfig

config = RequestContextConfig(context_adapter="context_logging")
app = RequestContextMiddleware(app, config=config)

# Now access logs will include request_id and correlation_id!
# Example: INFO [request_id=abc123] 127.0.0.1:8000 - "GET / HTTP/1.1" 200

Context-Logging Integration

The context-logging library provides scoped context that gets attached to log records. Combined with our formatters, this enables context in all logs including access logs:

import logging
from context_logging import setup_log_record
from fastapi_request_context import RequestContextMiddleware, RequestContextConfig
from fastapi_request_context.formatters import SimpleContextFormatter

# Enable context injection into log records (call once at startup)
setup_log_record()

# Configure logging with a context-aware formatter
handler = logging.StreamHandler()
handler.setFormatter(SimpleContextFormatter(
    fmt="%(levelname)s %(context)s %(message)s"
))
logging.basicConfig(handlers=[handler], level=logging.INFO)

# Use context-logging adapter
config = RequestContextConfig(context_adapter="context_logging")
app = RequestContextMiddleware(app, config=config)

When using the context-logging adapter, you can also add nested scoped context within a request using Context():

from context_logging import Context


@app.post("/process")
async def process_items():
    logger.info("Starting")  # [request_id=abc123]

    with Context(step=1):
        logger.info("Processing step 1")  # [request_id=abc123 step=1]
        await handle_step_1()

    with Context(step=2):
        logger.info("Processing step 2")  # [request_id=abc123 step=2]
        await handle_step_2()

    logger.info("Done")  # [request_id=abc123]
    return {"status": "ok"}

So, each log record will include the request context, and you can add nested scoped context within a request using Context().

Custom Context Adapter

You can implement custom adapters (e.g., Redis-backed) by implementing the ContextAdapter protocol. See examples/custom_adapter.py for a complete example.

Exception Context

When an exception occurs during request handling, the current context is automatically appended to the exception's args. This makes debugging easier by showing request context in error messages and tracebacks:

Example:

ValueError("Something went wrong", {"request_id": "abc123", "user_id": 456})

This behavior is compatible with the context-logging library - if context-logging already added context to an exception, it won't be added twice.

Validation Utilities

Ensure all routes and dependencies are async (required for proper context propagation):

from fastapi_request_context.validation import check_routes_and_dependencies_are_async


@app.on_event("startup")
async def validate():
    warnings = check_routes_and_dependencies_are_async(app)
    # Logs warnings for any sync routes/dependencies

    # Or raise an error
    check_routes_and_dependencies_are_async(app, raise_on_sync=True)

Streaming Responses with Context

When using streaming responses, the iteration happens outside the original request context. Use aiter_with_logging_context to preserve the logging context during iteration:

from fastapi import FastAPI
from fastapi.responses import StreamingResponse
from fastapi_request_context import aiter_with_logging_context, get_context, StandardContextField

app = FastAPI()


@app.get("/stream")
async def stream():
    async def generate():
        # Context is preserved here during iteration
        request_id = get_context(StandardContextField.REQUEST_ID)
        for i in range(10):
            yield f"chunk {i} (request: {request_id})\n"

    return StreamingResponse(aiter_with_logging_context(generate)())

Note: Requires context-logging extra: pip install fastapi-request-context[context-logging]

API Reference

Middleware

• RequestContextMiddleware(app, config=None) - Main middleware class

Configuration

• RequestContextConfig - Configuration dataclass with all options

Context Functions

• set_context(key, value) - Set a context value
• get_context(key) - Get a context value (returns None if not set)
• get_full_context() - Get all context values as a dict
• aiter_with_logging_context(func) - Preserve logging context in async iterators (requires context-logging)

Fields

• StandardContextField - Built-in fields (REQUEST_ID, CORRELATION_ID)

Adapters

• ContextAdapter - Protocol for custom adapters
• ContextVarsAdapter - Default adapter using Python's contextvars
• ContextLoggingAdapter - Adapter using context-logging library (enables access log integration)

Formatters

• JsonContextFormatter - JSON formatter for structured logging
• SimpleContextFormatter - Human-readable formatter with inline context

Validation

• is_async(func) - Check if a function is async
• check_dependencies_are_async(deps) - Check dependencies
• check_routes_and_dependencies_are_async(app) - Check entire app

Why This Library?

vs. Manual Implementation

Feature	Manual	This Library
Request ID generation	DIY	✅ Built-in
Correlation ID	DIY	✅ Built-in
Response headers	DIY	✅ Automatic
Context storage	DIY	✅ Pluggable
Logging integration	DIY	✅ Included
Type safety	Maybe	✅ Full
Tests	Maybe	✅ 100% coverage

vs. Other Libraries

• Zero dependencies beyond FastAPI (optional extras available)
• Pluggable adapters - not locked to one context library
• Validation utilities - catch sync code issues early
• Production-ready formatters - JSON and local dev support

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

# Clone the repo
git clone https://github.com/ADR-007/fastapi-request-context.git
cd fastapi-request-context

# Install dependencies
uv sync --all-extras

# Run tests
make test

# Run linting
make lint

# Fix linting issues
make lint-fix

License

MIT License - see LICENSE for details.