csrd-logging 0.2.0

Context-enriched logging mixin with optional auto-instrumentation

csrd.logging

Context-enriched logging for all application layers.

Dependency tier

Tier 1        csrd.models · csrd.lifespan · csrd.context
Tier 1.5      csrd.logging  ← depends on csrd.context only
Tier 2        csrd.delegate · csrd.repository · csrd.service
Tier 3        csrd.versioning

Components

ContextLogger

A stdlib Logger wrapper that auto-enriches every message with request context (hit_id, user_id, path params) as key=value pairs.

from csrd.logging import ContextLogger

logger = ContextLogger(logging.getLogger(__name__))
logger.info("Order created", meta={"order_id": 42})
# → "Order created hit_id=abc-123 user_id=user1 order_id=42"

All standard logging kwargs (exc_info, extra, stacklevel) pass through. The meta kwarg adds extra key=value pairs per call.

LoggingMixin

A mixin providing self.log (a ContextLogger) for any class. Works at every layer.

from csrd.logging import LoggingMixin

class OrderService(BaseService, LoggingMixin):
    async def place_order(self, cart):
        self.log.info("Placing order", meta={"items": len(cart)})

Auto-logging (opt-in)

Pass auto_log=True to automatically log entry and exceptions for every public method:

class OrderService(BaseService, LoggingMixin, auto_log=True):
    async def place_order(self, cart):  # ← entry logged at INFO, exceptions at ERROR
        ...

Exclude noisy methods:

class MyService(BaseService, LoggingMixin, auto_log=True):
    __log_exclude__ = {"health_check"}

Both sync and async methods are handled. Private methods (_name) are always skipped.

RequestContextFilter

A stdlib logging.Filter that injects context fields into log records (not messages). Use this when your logging backend (Splunk, ELK, Datadog) needs structured fields in a configurable format.

Fields added to each record:

Field	Source	Default
hit_id	Request trace ID	"-"
user_id	Authenticated user's sub claim	"-"
app_id	Application identifier header	"-"
api_version	Resolved API version	"-"

Production logging configuration

ContextLogger enriches log messages — it works out of the box with zero configuration. For production deployments you'll typically also want to configure stdlib logging with structured formatters, handlers, and filters.

Approach 1: ContextLogger only (simplest)

No configuration needed. Messages include context automatically:

2025-07-15 10:23:45 INFO  Order created hit_id=abc-123 user_id=user1 order_id=42

Good for development and simple deployments.

Approach 2: YAML logging configuration (production)

Create a config/logging.yml in your application:

version: 1
disable_existing_loggers: false

formatters:
  structured:
    style: "{"
    format: "{asctime} hitId={hit_id} userId={user_id} module={name} func={funcName} level={levelname} {message}"

filters:
  context:
    "()": csrd.logging.RequestContextFilter

handlers:
  console:
    class: logging.StreamHandler
    level: INFO
    formatter: structured
    stream: ext://sys.stdout
    filters: [context]

loggers:
  uvicorn:
    handlers: [console]
    level: INFO
    propagate: false
  uvicorn.access:
    handlers: [console]
    level: INFO
    propagate: false
  root:
    level: INFO
    handlers: [console]

Load it at startup:

import logging.config
import yaml
from pathlib import Path

with open(Path("config/logging.yml")) as f:
    logging.config.dictConfig(yaml.safe_load(f))

Approach 3: Both together (recommended for production)

Use ContextLogger / LoggingMixin in your code for dev-friendly messages, and attach RequestContextFilter to your production handlers for structured logging backends. The two are complementary — ContextLogger enriches the message text, RequestContextFilter adds record-level fields for formatters.

When to use which

Approach	Context in logs	Config required	Best for
ContextLogger	In message text (key=value)	None	Dev, simple apps
logging.yml + RequestContextFilter	In log record fields	YAML file	Splunk, ELK, structured logging
Both together	Both	YAML file	Full production setup

Installation

uv add csrd-logging