evan-logger 0.1.1

Structured colored logger with trace/span context and sampling

Project logger

A production-ready Python logging framework designed for modern backends and AI pipelines.

It supports:

• Structured JSON logs (ELK / GCP Logging / Datadog ready)
• Trace + Span IDs (contextvars, async-safe)
• Automatic context (file:line Class.method())
• Per-module log levels
• Sampling filters for hot paths (reduce noise + cost)

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Table of Contents

• Overview
• Architecture
• Features
• Installation
• Usage
• Configuration
• Project Structure
• Development
• Testing
• Deployment
• Roadmap
• Contributing
• License
• Contact

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Overview

This project provides a clean, extensible logging layer for Python services.

It’s built to solve common production pain points:

• Logs without structure are hard to search
• Async + threads break context
• Trace correlation is missing
• Hot loops spam logs and increase cloud costs
• Large codebases need per-module control

This logger provides a single unified API for:

• console logs (pretty + colored)
• file logs (JSON structured)
• trace/span correlation
• sampling

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Architecture

LoggerConfig
    ↓
Logger (singleton)
    ↓
logging.Logger (stdlib)
    ↓
Handlers
    ├── Console handler (colored)
    └── File handler (.log or .json)
    ↓
Filters
    └── SamplingFilter
    └── DeterministicFilter
    ↓
ContextLogger (LoggerAdapter)
    ├── context
    ├── trace_id
    └── span_id

Core Components:

1. API Layer: Interfaces (CLI, SDK, REST) for uploading and managing files
2. Service Layer: Business logic for versioning and lifecycle rules
3. Repository Layer: Abstract persistence interfaces for storage and metadata
4. Infrastructure Layer: Cloud storage providers and NoSQL database adapters

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Features

1. Structured JSON logging

   • Compatible with ELK, GCP Logging, Datadog, Splunk
   • Includes context, trace_id, span_id, module, function, line, exception

2. Trace + Span IDs

   • Uses contextvars (async-safe)
   • Supports manual trace/span injection

3. Automatic context resolution

   • Adds file:line Class.method() automatically
   • Works for functions, methods, decorators

4. Per-module log levels

   • Example: src.core=WARNING while the rest stays INFO

5. Sampling filter

   • Sample DEBUG/INFO logs for noisy paths
   • Always keep WARNING/ERROR/CRITICAL

6. Singleton logger factory

   • Global configuration
   • Safe Logger.configure(...) entrypoint

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Installation

pip install <url>

Or install from source:

git clone <url>
cd project-name
pip install -e .

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Usage

Basic setup

import logging
from src.logger import Logger
from src.config import LoggerConfig

Logger.configure(
    LoggerConfig(
        name="app",
        level=logging.INFO,
        directory="logs",
        json_logs=True,
        sample_rate=0.2,
        module_levels={
            "src.core": logging.WARNING,
        },
    )
)

logger = Logger().bind("startup")
logger.info("Service initialized")

Trace + ID span

from src.logger import Logger

log = Logger()
log.set_trace()
log.set_span()

logger = log.bind("request")
logger.info("Request started")

JSON logs example output

{
  "timestamp": "2026-02-04T10:55:01.140Z",
  "level": "INFO",
  "message": "Request started",
  "logger": "app",
  "context": "api.py:88 EDDController.calculate()",
  "trace_id": "a1f29c...",
  "span_id": "91c77d...",
  "module": "api",
  "function": "calculate",
  "line": 88
}

---

Configuration

Configuration is done through LoggerConfig.

Example:

from src.config import LoggerConfig

config = LoggerConfig(
    name="service",
    directory="logs",
    json_logs=True,
    sample_rate=0.1,
    level=logging.INFO,
    module_levels={
        "src.core": logging.WARNING,
        "google": logging.ERROR,
        "httpx": logging.ERROR,
    },
)

Key settings

Field	Meaning
json_logs	Output JSON logs for file handler
directory	Where log files are stored
deterministic	Enable deterministic logging
sample_rate	Sampling probability for INFO/DEBUG
module_levels	Per-module log level override
level	Global log level
name	Logger name

---

Project Structure

src/
 ├── logger.py              # Logger singleton + ContextLogger
 ├── config.py              # LoggerConfig + JSONFormatter + SamplingFilter
 ├── core/
 │    ├── filters.py        # Log filtering logic
 │    ├── formatters.py     # Log formatting logic
 │    └── tracer.py         # contextvars trace_id/span_id
 └── decorators/
      ├── functions.py      # function_log decorator
      └── classes.py        # class_log decorator

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Development

pip install -r requirements-dev.txt

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Testing

pytest tests/

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Deployment

The service can be deployed as:

Python SDK library
FastAPI microservice
Serverless function (Cloud Run / Lambda / Azure Functions)
Internal data platform component

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Roadmap

1. Request middleware integration for Flask/FastAPI
2. Deterministic sampling by trace_id (avoid partial traces)
3. Rotating file handler support
4. OpenTelemetry bridge
5. Log batching / async writer for high throughput

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Contributing

Contributions are welcome. Please follow the coding standards and submit PRs with tests and documentation updates.

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License

MIT License.

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Contact

Maintainer: Evan Flores Email: [e-mail] Organization: Liverpool