db_operations/db_operations.py

import pymongo
import os
import pandas as pd
import logging


class DBOperations:
    """
    Reads news from MongoDB
    """
    def __init__(self):
        self.url = os.getenv('DB_URL')
        self.database = "rss_news_db_cat_pred_sim_news"
        self.collection = "rss_news_cat_pred_sim_news"
        self.__client = None
        self.__error = 0

    async def __connect(self):
        try:
            self.__client = pymongo.MongoClient(self.url)
            _ = self.__client.list_database_names()
        except Exception as conn_exception:
            self.__error = 1
            logging.critical(f"Error in DBOperations.connect(): {conn_exception}")
            self.__client = None
            raise

    async def __read(self):
        try:
            db = self.__client[self.database]
            coll = db[self.collection]
            docs = []
            maxtries = 5
            ntry = 0
            
            while (len(docs) == 0) and (ntry < maxtries):
                for doc in coll.find():
                    docs.append(doc)
                ntry += 1
                logging.info(f"DB Read try: {ntry}")    
                
            rss_df = pd.DataFrame(docs)
        except Exception as insert_err:
            self.__error = 1
            logging.critical(f"Error in DBOperations.read(): {insert_err}")
            rss_df = pd.DataFrame({'_id': '', 'title': '', 'url': '',
                                   'description': '', 'parsed_date': '',
                                   'src': ''}, index=[0])
        return rss_df

    def __close_connection(self):
        if self.__client is not None:
            self.__client.close()
            self.__client = None

    async def read_news_from_db(self):
        rss_df = pd.DataFrame({'_id': '', 'title': '', 'url': '',
                               'description': '', 'parsed_date': '',
                               'src': ''}, index=[0])
        if self.url is not None:
            if self.__error == 0:
                await self.__connect()
            if self.__error == 0:
                rss_df = await self.__read()
            if self.__error == 0:
                logging.info("Read Successful")
            if self.__client is not None:
                self.__close_connection()
        return rss_df