Mongo Lock

lock_mongo.ipynb

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    "### LOCK DISTRIBUIDO COM PYTHON E MONGO\n",
    "\n",
    "Para utilizar esse recurso foi criada uma collection no mongo com índice único para chaves de locks, essas chaves são excluidas automaticamente ao finalizar algum procedimento.\n",
    "\n",
    "Por segurança foi criado um índice ttl no mongo com isso as chaves que não forem excluídas pelo python serão excluídas automaticamente pelo mongo depois de 2 minutos."
   ]
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   "cell_type": "markdown",
   "id": "d58adee5-6c77-4a66-8f7e-6881977530e4",
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   "source": [
    "##### instalado a lib pymongo para conexão com mongodb"
   ]
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     "text": [
      "Requirement already satisfied: pymongo in /opt/conda/lib/python3.10/site-packages (4.3.3)\n",
      "Requirement already satisfied: dnspython<3.0.0,>=1.16.0 in /opt/conda/lib/python3.10/site-packages (from pymongo) (2.3.0)\n",
      "Note: you may need to restart the kernel to use updated packages.\n"
     ]
    }
   ],
   "source": [
    "%pip install pymongo"
   ]
  },
  {
   "cell_type": "markdown",
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   "source": [
    "### Criando os índices na collection lock para o database teste\n",
    "\n",
    "##### indice *key* para montar a chave do lock para se tornar único\n",
    "\n",
    "##### indice *created_at* é um ttl usado para o mongo excluir o registro automaticamente depois de 120 segundos"
   ]
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      "text/plain": [
       "'created_at_1'"
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   "source": [
    "from pymongo import MongoClient\n",
    "mongo_client = MongoClient('localhost', 27017)\n",
    "db = mongo_client['teste']\n",
    "db.lock.create_index([(\"key\", 1)],unique=True)\n",
    "db.lock.create_index( [( \"created_at\", 1 )], expireAfterSeconds= 120 )"
   ]
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  {
   "cell_type": "markdown",
   "id": "6ca89fbf-4939-411e-9a41-daa97795baf4",
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   "source": [
    "### Criando classe para controle de lock usando formato 'with statement'\n",
    "\n",
    "##### com esse formato ao usar a classe com with o python irá executar automaticamente o método __enter__ antes dos códigos e o método __exit__ ao finalizar, veja o exemplo nos testes posteriormente\n",
    "##### https://horadecodar.com.br/2020/04/20/para-que-serve-o-with-no-python-como-utilizar"
   ]
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   "source": [
    "from pymongo.errors import DuplicateKeyError\n",
    "import time\n",
    "from datetime import datetime\n",
    "class MongoLock():\n",
    "    def __init__(self, database: str, key: str):\n",
    "        self.database = database\n",
    "        self.key = key\n",
    "        \n",
    "    def __enter__(self):\n",
    "        while True:\n",
    "            try:\n",
    "                self.database.lock.insert_one({'key': self.key, 'created_at': datetime.utcnow()})\n",
    "                return self\n",
    "            except DuplicateKeyError:\n",
    "                print(f'waiting lock for key:{self.key}')\n",
    "\n",
    "    def __exit__(self, type, value, traceback):\n",
    "        self.database.lock.delete_one({'key': self.key})"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "74156a28-fd30-410d-b3a9-e52f11efcaa2",
   "metadata": {},
   "source": [
    "### Testes usando threads que para simular um ambiente distribuído"
   ]
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   "id": "9a23d1c5-6640-4544-bfe5-30dcfe66259b",
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   "source": [
    "from pymongo import MongoClient\n",
    "mongo_client = MongoClient('localhost', 27017)\n",
    "db = mongo_client['teste']\n",
    "\n",
    "def teste_lock(nome):\n",
    "    print(nome)\n",
    "    seller_id = 'coisinhadejesus'\n",
    "    sku = '0123456678'\n",
    "    with MongoLock(db, seller_id+sku) as m:\n",
    "        print(f\"passei pelo lock {nome}\")"
   ]
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     "text": [
      "thread 1\n",
      "thread 2\n",
      "passei pelo lock thread 1\n",
      "thread 3\n",
      "thread 4\n",
      "thread 5\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "thread 6\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "passei pelo lock thread 5\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "passei pelo lock thread 3\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "passei pelo lock thread 2\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "passei pelo lock thread 4\n",
      "waiting lock for key:coisinhadejesus0123456678\n",
      "passei pelo lock thread 6\n"
     ]
    }
   ],
   "source": [
    "from threading import Thread\n",
    "from time import sleep\n",
    "\n",
    "t1 = Thread(target = teste_lock, args=['thread 1'])\n",
    "t2 = Thread(target = teste_lock, args=['thread 2'])\n",
    "t3 = Thread(target = teste_lock, args=['thread 3'])\n",
    "t4 = Thread(target = teste_lock, args=['thread 4'])\n",
    "t5 = Thread(target = teste_lock, args=['thread 5'])\n",
    "t6 = Thread(target = teste_lock, args=['thread 6'])\n",
    "\n",
    "t1.start()\n",
    "t2.start()\n",
    "t3.start()\n",
    "t4.start()\n",
    "t5.start()\n",
    "t6.start()\n",
    "\n",
    "sleep(0.2)\n",
    "\n",
    "t1.join()\n",
    "t2.join()\n",
    "t3.join()\n",
    "t4.join()\n",
    "t5.join()\n",
    "t6.join()"
   ]
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