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   "source": [
    "# Creating and processing logs\n",
    "\n",
    "## Goals\n",
    "  \n",
    "  - importance of logging\n",
    "  - configuring logger module\n",
    "  - open log files\n",
    "  \n",
    "## modules"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "from __future__ import print_function\n",
    "\n",
    "import logging\n",
    "import logging.config\n",
    "import logging.handlers\n",
    "import mimetypes\n",
    "import gzip, bz2\n",
    "import yaml\n",
    "\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Importance of Logging\n",
    "\n",
    "All automation and scripting activity should be carefully logged.\n",
    "\n",
    "The ```logging``` module:\n",
    "\n",
    "  - can stream logs to files and network\n",
    "  - is configurable via yml \n",
    "  - optimizes output via log levels\n",
    "  - takes care of rotation\n",
    "  \n",
    "Hint: manage logs with syslog.\n",
    "  "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {
    "collapsed": false
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   "outputs": [],
   "source": [
    "\n",
    "# Logs to stdout|err with a default loglevel.\n",
    "# Logs are not printed on jupyter cells but you can  \n",
    "#  check them in another terminal with\n",
    "#  #docker-compose logs\n",
    "logging.basicConfig(level=logging.DEBUG)\n",
    "\n",
    "# Create a logger.\n",
    "log = logging.getLogger()\n",
    "\n",
    "# Logs supports a print-like syntax, and doesn't \n",
    "#  build unneeded message strings. \n",
    "log.info(\"Use %r instead of %s to avoid\", [u\"Serialization\"], \"issues\")\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "version: 1\r\n",
      "formatters:\r\n",
      "  detailed: \r\n",
      "    class: logging.Formatter\r\n",
      "    format: '%(asctime)s %(name)-15s %(levelname)-8s %(processName)-10s %(message)s'\r\n",
      "\r\n",
      "handlers:\r\n",
      "  console: \r\n",
      "    class: logging.StreamHandler\r\n",
      "    level: INFO\r\n",
      "  syslog: \r\n",
      "    class: logging.handlers.SysLogHandler\r\n",
      "    formatter: detailed\r\n",
      "    level: DEBUG\r\n",
      "\r\n",
      "loggers:\r\n",
      "  os:\r\n",
      "    handlers: [syslog]\r\n",
      "\r\n",
      "root:\r\n",
      "  handlers: [console, syslog]\r\n",
      "  level: DEBUG\r\n"
     ]
    }
   ],
   "source": [
    "\n",
    "%cat logger.yml\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {
    "collapsed": false
   },
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      "To syslog\n"
     ]
    }
   ],
   "source": [
    "with open('logger.yml') as logger_config:\n",
    "    logging.config.dictConfig(yaml.safe_load(logger_config))\n",
    "    \n",
    "# The ```os``` module goes to syslog\n",
    "log.info(\"To syslog\")\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {
    "collapsed": true
   },
   "outputs": [],
   "source": [
    "# To process compressed files, use an helper function. \n",
    "import mimetools\n",
    "import gzip\n",
    "import bz2\n",
    "\n",
    "def log_open(path):\n",
    "    \"\"\"Open log files using its mimetype to choose the correct method\"\"\"\n",
    "    l_type, l_encoding = mimetypes.guess_type(path)\n",
    "    if l_encoding == 'gzip':\n",
    "        return gzip.open(path, 'rb')\n",
    "    elif l_encoding == 'bzip2':\n",
    "        return bz2.BZ2File(path, 'rb')\n",
    "    else:\n",
    "        return open(path, 'rb')\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {
    "collapsed": false
   },
   "outputs": [],
   "source": [
    "# Exercise:\n",
    "#  log some messages modifying the default format string.\n",
    "#  check the outcome in a separate terminal with\n",
    "#  docker-compose logs"
   ]
  }
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