Closing amqp promise connection after publishing?

Question

I'm trying to work out how to close my promise based connections after publishing messages.

I've tried to extrapolate away shared code for my sender and my receiver, so I have a connection file like this:

connector.js

const amqp = require('amqplib');
class Connector {
  constructor(RabbitMQUrl) {
    this.rabbitMQUrl = RabbitMQUrl;
  }

  connect() {
    return amqp.connect(this.rabbitMQUrl)
      .then((connection) => {
        this.connection = connection;
        process.once('SIGINT', () => {
          this.connection.close();
        });
        return this.connection.createChannel();
      })
      .catch( (err) => {
        console.error('Errrored here');
        console.error(err);
      });
  }
}

module.exports = new Connector(
  `amqp://${process.env.AMQP_HOST}:5672`
);

Then my publisher/sender looks like this:

publisher.js

const connector = require('./connector');

class Publisher {
  constructor(exchange, exchangeType) {
    this.exchange = exchange;
    this.exchangeType = exchangeType;
    this.durabilityOptions = {
      durable: true,
      autoDelete: false,
    };
  }

  publish(msg) {
    connector.connect()
      .then( (channel) => {
        let ok = channel.assertExchange(
          this.exchange,
          this.exchangeType,
          this.durabilityOptions
        );
        return ok
          .then( () => {
            channel.publish(this.exchange, '', Buffer.from(msg));
            return channel.close();
          })
          .catch( (err) => {
            console.error(err);
          });
      });
  }
}

module.exports = new Publisher(
  process.env.AMQP_EXCHANGE,
  process.env.AMQP_TOPIC
);

But as said, I can't quite work out how to close my connection after calling publish().

Terry Lennox · Answer 1 · 2018-01-08T17:54:02.473

You could add a close() function to connector:

  close() {
      if (this.connection) {
          console.log('Connector: Closing connection..');
          this.connection.close();
      }
  }

Publisher:

class Publisher {
  constructor(exchange, exchangeType) {
    this.exchange = exchange;
    this.exchangeType = exchangeType;
    this.durabilityOptions = {
      durable: true,
      autoDelete: false,
    };
  }

  connect() {
      return connector.connect().then( (channel) => {
         console.log('Connecting..');
         return channel.assertExchange(
          this.exchange,
          this.exchangeType,
          this.durabilityOptions
        ).then (() => {  
            this.channel = channel;
            return Promise.resolve();
        }).catch( (err) => {
            console.error(err);
        });;
      });
  }

  disconnect() {
      return this.channel.close().then( () => { return connector.close();});
  }

  publish(msg) {
      this.channel.publish(this.exchange, '', Buffer.from(msg));      
  };

}

Test.js

'use strict'

const connector = require('./connector');
const publisher = require('./publisher');


publisher.connect().then(() => { 
    publisher.publish('message');
    publisher.publish('message2');
    publisher.disconnect();
});

hmmm doing it this way is throwing up errors for me, like: `Unhandled rejection IllegalOperationError: Connection closing` — Jarede, Jan 08 '18 at 16:49
Yes, if you call publish() twice in succession, you'll get the error since the response is a promise and the channel is being closed when you make the call. You'd have to do something like publish('message').then(() => { publish('message2');}); — Terry Lennox, Jan 08 '18 at 17:28
I'd actually make the suggestion that you would open the connection and channel in the publisher and only close when you're done rather than after each publish() call. — Terry Lennox, Jan 08 '18 at 17:34
Ahhh yeah i was trying to DRY up my code for the publisher and the sender since there's so much shared code. — Jarede, Jan 08 '18 at 17:40

Closing amqp promise connection after publishing?

1 Answers1