dbConnection

dbConnection.js

const mongoose = require('mongoose');
const errorResp = function (err) {
    return {
        message: 'Unable to connect to DB',
        errorCode: 40
    };
};
// Export DB Connection function
mongoose.Promise = global.Promise;
module.exports = function (options, callback) {

    if (global && global.cachedConnection && global.cachedConnection.readyState && global.cachedConnection.readyState === 1) {

        return global.connectionPromise;
    } else {
 
        console.log('No connection Found. Creating connection !!!');
        try {
            let connectionPromise = mongoose.connect(fooURL, {
                useMongoClient: true,
                poolSize: (options && options.poolSize) ? options.poolSize : 2,
                connectTimeoutMS: 30000,
                socketTimeoutMS: 30000,
                keepAlive: 120
            });
            global.connectionPromise = connectionPromise;
            connectionPromise.then((db) => {


                if (mongoose.connection) {

                    let connection = mongoose.connection;
                    global.cachedConnection = connection;

                    connection.on('error', function (err) {
                        global.cachedConnection = null;
                    });

                    connection.on('disconnected', function () {
                        global.cachedConnection = null;
                    });

                    connection.on('close', function () {
                        global.cachedConnection = null;
                    });

                    process.on('SIGINT', function () {
                        connection.close(function () {
                            process.exit(0);
                        });
                    });
                } else {
                    global.cachedConnection = null;
                }
            }, (reason) => {

                global.cachedConnection = null; //Retry connection during next call
                return callback(errorResp(reason));
            });
            return global.connectionPromise;
        } catch (error) {

            console.error(error);
            global.cachedConnection = null;
            return callback(errorResp(error));
        }
    }

};