CODEWITHSUNDEEP
node.jsmongodbdesign-patternsredis
twcardenas
twcardenas

Reputation: 135

All Connections connect before app is Served

I have an application that has connects to Redis, Mongo, and Elasticsearch but how can I make sure all the connections are connected before the app is served? I notice that Elasticsearch usually takes longer and when I test my app using Supertest that the database connects but the console.info('Successfully connected to db'); doesn't log to the console before the tests start to run.

server.ts

const client = redis.createClient({ host: process.env.REDIS })


client.on('connect', function () {
    console.log('Redis client connected');
});

mongoose
      .connect(dbURL)
      .then(() => {
        return console.info(`Successfully connected to ${db}`);
      })
      .catch(error => {
        console.error('Error connecting to database: ', error);
        return process.exit(1);
      });
  };
const app = express();
export default app;

main.ts

import server from './server'
server.listen(8000)

Upvotes: 0

Views: 49

Answers (2)

Javier Brea
Javier Brea

Reputation: 1415

You should "promisify" all your connection processes, and then wait for all promises to be resolved before starting the app:

import server from './server'

const connectRedis = host => {
  return new Promise(resolve => {
    const client = redis.createClient({ host });

    client.on("connect", () => {
      console.log("Redis client connected");
      resolve(client);
    });
  });
}

const connectMongo = dbURL => {
  return mongoose.connect(dbURL)
};

const connectAll = ({ mongoDbURL, redisHost }) => {
  return Promise.all([
    connectRedis(redisHost),
    connectMongo(mongoDbURL)
  ]);
}

connectAll({
  mongoDbUrl: process.env.MONGODB_URL,
  redisHost: process.env.REDIS,
}).then(() => {
  server.listen(8000)
});

Upvotes: 1

Tuan Anh Tran
Tuan Anh Tran

Reputation: 7267

You can export a connection Promise for each of the connection

and then in the main app, do this

Promise.all([
  connectRedisPromise(),
  connectMongoPromise(),
  connectESPromise(),
]).then(() => {
  // start the app
})

Upvotes: 1

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