14-Logging.ipynb

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    "# Logging"
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    "# Logging\n",
    "* Logging is a means of tracking events that happen when some software runs\n",
    "* We add logging calls to our code to indicate that certain events have occurred\n",
    "* Events have an importance which we, the developer, ascribe to the event; the importance can also be called the level or severity\n",
    "* There are set of convenience functions for simple logging usage: debug(), info(), warning(), error(), and critical()\n",
    "* When should we use logging? When we do use logging, which states should we use?\n",
    "* Python provides a standard and configurable logging facility. You can set up the collection\n",
    "of loggers &amp; handlers separately from their actual *use* in your program"
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   "source": [
    "![alt-text](loggingLevels.jpg \"Logging Levels\")"
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     "text": [
      "warning\n"
     ]
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    "print('warning')"
   ]
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      "WARNING:root:Watch out!\n"
     ]
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   "source": [
    "import logging\n",
    "from importlib import reload\n",
    "# need to reload logging module because Jupyter already imports and\n",
    "# sets up a logger\n",
    "# you don't need to do this outside of Jupyter\n",
    "reload(logging)\n",
    "logging.warning('Watch out!')\n",
    "logging.info('not important')"
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     "text": [
      "DEBUG:root:This message should go to the log file\n",
      "INFO:root:So should this\n",
      "WARNING:root:And this, too\n"
     ]
    }
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   "source": [
    "#import logging\n",
    "from importlib import reload\n",
    "reload(logging)\n",
    "logging.basicConfig(filename='example.log',\n",
    "                    filemode='w',\n",
    "                    level=logging.DEBUG)\n",
    "\n",
    "logging.debug('This message should go to the log file')\n",
    "logging.info('So should this')\n",
    "logging.warning('And this, too')\n",
    "\n",
    "with open('example.log', 'r') as f:\n",
    "    for line in f:\n",
    "        print(line, end='')"
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     "text": [
      "DEBUG:root:This message should go to the log file\n",
      "INFO:root:So should this\n",
      "WARNING:root:And this, too\n"
     ]
    }
   ],
   "source": [
    "%%bash\n",
    "cat example.log"
   ]
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     "text": [
      "2022-05-26 13:48:45,296 - DEBUG - This message should go to the log file\n",
      "2022-05-26 13:48:45,297 - INFO - So should this\n",
      "2022-05-26 13:48:45,297 - WARNING - And this, too\n"
     ]
    }
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   "source": [
    "# same example but with more detailed logging\n",
    "# configuration\n",
    "# ...instead of basicConfig\n",
    "#import logging\n",
    "from importlib import reload\n",
    "reload(logging)\n",
    "logger = logging.getLogger()\n",
    "fhandler = logging.FileHandler(filename='example2.log', mode='w')\n",
    "formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')\n",
    "fhandler.setFormatter(formatter)\n",
    "logger.addHandler(fhandler)\n",
    "logger.setLevel(logging.DEBUG)\n",
    "\n",
    "logging.debug('This message should go to the log file')\n",
    "logging.info('So should this')\n",
    "logging.warning('And this, too')\n",
    "\n",
    "with open('example2.log', 'r') as f:\n",
    "    for line in f:\n",
    "        print(line, end='')"
   ]
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    "# Example of setting the log level via the command line\n",
    "import logging\n",
    "import sys\n",
    "\n",
    "LEVELS = { 'debug': logging.DEBUG,\n",
    "            'info': logging.INFO,\n",
    "            'warning': logging.WARNING,\n",
    "            'error': logging.ERROR,\n",
    "            'critical': logging.CRITICAL\n",
    "}\n",
    "\n",
    "if len(sys.argv) > 1:\n",
    "    level_name = sys.argv[1]\n",
    "    level = LEVELS.get(level_name, logging.NOTSET)\n",
    "    logging.basicConfig(level=level)\n",
    "\n",
    "logging.debug('This is a debug message')\n",
    "logging.info('This is an info message')\n",
    "logging.warning('This is a warning message')\n",
    "logging.error('This is an error message')\n",
    "logging.critical('This is a critical error message')"
   ]
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   "source": [
    "%%bash\n",
    "python3 logargv.py debug"
   ]
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   "source": [
    "from importlib import reload\n",
    "reload(logging)\n",
    "\n",
    "logging.basicConfig(level=logging.WARNING)\n",
    "\n",
    "logger1 = logging.getLogger('module1')\n",
    "logger2 = logging.getLogger('module2')\n",
    "\n",
    "logger1.warning('This message comes from one module')\n",
    "logger2.warning('And this message comes from another module')\n",
    "\n",
    "logger2.setLevel(logging.CRITICAL)\n",
    "logger2.warning('We will not see this...')"
   ]
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   "source": [
    "### Lab: Logging\n",
    "* create two classes, each of which declares its own logger\n",
    "* add a method to each class which uses the logger from its class\n",
    "* instantiate the classes and invoke the methods to demonstrate that both loggers are being used"
   ]
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   "source": [
    "## Practical considerations\n",
    "\n",
    "Here are some practical considerations for logging:\n",
    "1. How quickly do logs accumulate?\n",
    "1. How long do you need to keep them?\n",
    "1. How do you want to organize your logs?\n",
    "1. How frequently should you rotate logs?\n",
    "1. What are common log access patterns?\n",
    "1. How do you mask logs to avoid PII issues?\n",
    "\n"
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