Comparison_Project/app/services/logger_service.py

import os
import logging
from logging.handlers import RotatingFileHandler
from flask import request, session, has_request_context


class RequestContextFilter(logging.Filter):
    """Adds request information to every log record."""

    def filter(self, record):

        if has_request_context():
            record.user = session.get("user_name", "Anonymous")
            record.ip = request.remote_addr or "Unknown"
            record.method = request.method
            record.url = request.url
        else:
            record.user = "System"
            record.ip = "-"
            record.method = "-"
            record.url = "-"

        return True


class LoggerService:

    LOG_DIR = "logs"

    APP_LOG = "app.log"
    ERROR_LOG = "error.log"
    DEBUG_LOG = "debug.log"

    MAX_BYTES = 10 * 1024 * 1024      # 10 MB
    BACKUP_COUNT = 10

    @classmethod
    def init_app(cls, app):

        os.makedirs(cls.LOG_DIR, exist_ok=True)

        formatter = logging.Formatter(
            fmt=(
                "%(asctime)s | "
                "%(levelname)-8s | "
                "User=%(user)s | "
                "IP=%(ip)s | "
                "%(method)s | "
                "%(url)s | "
                "%(message)s"
            ),
            datefmt="%Y-%m-%d %H:%M:%S"
        )

        context_filter = RequestContextFilter()

        # Remove default handlers
        app.logger.handlers.clear()

        # ==========================
        # Application Log
        # ==========================
        app_handler = RotatingFileHandler(
            os.path.join(cls.LOG_DIR, cls.APP_LOG),
            maxBytes=cls.MAX_BYTES,
            backupCount=cls.BACKUP_COUNT,
            encoding="utf-8"
        )

        app_handler.setLevel(logging.INFO)
        app_handler.setFormatter(formatter)
        app_handler.addFilter(context_filter)

        # ==========================
        # Error Log
        # ==========================
        error_handler = RotatingFileHandler(
            os.path.join(cls.LOG_DIR, cls.ERROR_LOG),
            maxBytes=cls.MAX_BYTES,
            backupCount=cls.BACKUP_COUNT,
            encoding="utf-8"
        )

        error_handler.setLevel(logging.ERROR)
        error_handler.setFormatter(formatter)
        error_handler.addFilter(context_filter)

        # ==========================
        # Debug Log
        # ==========================
        debug_handler = RotatingFileHandler(
            os.path.join(cls.LOG_DIR, cls.DEBUG_LOG),
            maxBytes=cls.MAX_BYTES,
            backupCount=cls.BACKUP_COUNT,
            encoding="utf-8"
        )

        debug_handler.setLevel(logging.DEBUG)
        debug_handler.setFormatter(formatter)
        debug_handler.addFilter(context_filter)

        # ==========================
        # Console Log
        # ==========================
        console_handler = logging.StreamHandler()

        console_handler.setLevel(logging.INFO)
        console_handler.setFormatter(formatter)
        console_handler.addFilter(context_filter)

        # ==========================
        # Logger Configuration
        # ==========================
        app.logger.setLevel(logging.DEBUG)

        app.logger.addHandler(app_handler)
        app.logger.addHandler(error_handler)
        app.logger.addHandler(debug_handler)
        app.logger.addHandler(console_handler)

        # ==========================
        # Automatic Request Logging
        # ==========================
        @app.before_request
        def before_request():
            app.logger.info("Request Started")

        @app.after_request
        def after_request(response):
            app.logger.info(
                f"Request Completed | Status={response.status_code}"
            )
            return response

        # ==========================
        # Exception Logging
        # ==========================
        @app.errorhandler(Exception)
        def log_exception(error):

            app.logger.exception(
                f"Unhandled Exception: {str(error)}"
            )

            raise error

        app.logger.info("=" * 70)
        app.logger.info("Application Started Successfully")
        app.logger.info("=" * 70)