How to do health check for MongoJS in NodeJS

Here's an example of an event-based solution in Node.js to handle MongoDB connection health checks:

const EventEmitter = require('events');
const MongoClient = require('mongodb').MongoClient;

const MONGO_URI = 'mongodb://localhost:27017/mydb';

class MongoDBHealthCheck extends EventEmitter {
  constructor() {
    super();
    this.mongoClient = new MongoClient(MONGO_URI, { useNewUrlParser: true });
    this.isHealthy = false;
  }

  start() {
    this.mongoClient.connect((err) => {
      if (err) {
        console.error('Failed to connect to MongoDB:', err);
        this.isHealthy = false;
        this.emit('healthCheckFailed');
      } else {
        console.log('Connected to MongoDB.');
        this.isHealthy = true;
        this.emit('healthCheckSucceeded');
      }
    });
  }

  stop() {
    this.mongoClient.close();
  }

  getStatus() {
    return this.isHealthy;
  }
}

const mongoDBHealthCheck = new MongoDBHealthCheck();

// Event listener
mongoDBHealthCheck.on('healthCheckSucceeded', () => {
  console.log('MongoDB connection is healthy.');
});

mongoDBHealthCheck.on('healthCheckFailed', () => {
  console.error('MongoDB connection is unhealthy.');
});

// Start the health check
mongoDBHealthCheck.start();

In this example, we're creating a MongoDBHealthCheck class that extends the EventEmitter class. The MongoDBHealthCheck class encapsulates the logic for checking the health of the MongoDB connection.

The start() method connects to the MongoDB server and emits either the healthCheckSucceeded or healthCheckFailed event depending on whether the connection was successful.

The getStatus() method returns the current status of the connection (either true for healthy or false for unhealthy).

We're also setting up event listeners to handle the healthCheckSucceeded and healthCheckFailed events. When the healthCheckSucceeded event is emitted, we log a message saying that the MongoDB connection is healthy. When the healthCheckFailed event is emitted, we log an error message saying that the MongoDB connection is unhealthy.

Finally, we create an instance of the MongoDBHealthCheck class and start the health check by calling the start() method.