Node.js中基于Redis配置实现MongoDB多库单例连接方案问询

Hey there! Let's build out your dbConnection.js properly to meet your requirements: fetching MongoDB config from Redis, creating a singleton connection, and handling all async logic cleanly.

const { MongoClient } = require('mongodb');
const redis = require('redis');
const { promisify } = require('util');

// Initialize Redis client (adjust Redis config as per your setup)
const redisClient = redis.createClient({
  host: 'localhost', // your Redis host
  port: 6379         // your Redis port
});

// Promisify Redis get method for async/await usage
const getRedisConfig = promisify(redisClient.get).bind(redisClient);

// Singleton MongoDB connection instance
let dbInstance = null;

/**
 * Fetch MongoDB config from Redis and create a singleton connection
 * @returns {Promise<MongoClient>} MongoDB database instance
 */
async function getMongoConnection() {
  // Check if we already have a valid connected instance
  if (dbInstance && dbInstance.topology.isConnected()) {
    console.log('Reusing existing MongoDB connection');
    return dbInstance;
  }

  try {
    // Step 1: Fetch MongoDB config from Redis
    // Assuming you've stored the config as a JSON string in Redis with key "mongodb_config"
    const configJson = await getRedisConfig('mongodb_config');
    if (!configJson) {
      throw new Error('MongoDB config not found in Redis');
    }

    const mongoConfig = JSON.parse(configJson);
    const { username, password, host, port, dbName } = mongoConfig;

    // Step 2: Build MongoDB connection string
    let connectionString;
    if (username && password) {
      connectionString = `mongodb://${username}:${encodeURIComponent(password)}@${host}:${port}/${dbName}?authSource=admin`;
    } else {
      connectionString = `mongodb://${host}:${port}/${dbName}`;
    }

    // Step 3: Create new MongoDB connection
    const client = await MongoClient.connect(connectionString, {
      useNewUrlParser: true,
      useUnifiedTopology: true
    });

    dbInstance = client.db(dbName);
    console.log('New MongoDB connection established');
    return dbInstance;
  } catch (error) {
    console.error('Failed to connect to MongoDB:', error);
    throw error; // Re-throw to let caller handle the error
  }
}

// Optional: Method to reset the singleton instance (useful if config changes in Redis)
function resetMongoConnection() {
  if (dbInstance) {
    dbInstance.client.close();
    dbInstance = null;
    console.log('MongoDB connection reset');
  }
}

module.exports = {
  getMongoConnection,
  resetMongoConnection
};

• Singleton Pattern: We use the dbInstance variable to store the active connection. Every call to getMongoConnection() first checks if this instance exists and is connected—if so, it returns the existing one instead of creating a new connection.
• Redis Config Fetch: We promisify Redis's get method to use async/await, making the code easier to read. We assume your MongoDB config is stored as a JSON string in Redis (e.g., SET mongodb_config '{"username":"admin","password":"secret","host":"localhost","port":27017,"dbName":"mydb"}').
• Connection String Handling: We handle both authenticated and unauthenticated MongoDB setups, using encodeURIComponent() to safely escape special characters in the password.
• Error Handling: Proper try/catch blocks catch issues with Redis reads or MongoDB connections, and we re-throw errors so the caller can handle them appropriately (e.g., retry logic).
• Reset Function: The resetMongoConnection() method lets you invalidate the singleton instance if your Redis config changes—this way, the next call to getMongoConnection() will fetch the new config and create a fresh connection.

In your other files, you can use the connection like this:

const { getMongoConnection } = require('./dbConnection');

async function fetchData() {
  const db = await getMongoConnection();
  const users = await db.collection('users').find({}).toArray();
  console.log(users);
}

fetchData();

内容的提问来源于stack exchange，提问作者Subburaj