ng2 stomp client - how to re-subscribe after re-connecting?

Question

I am subscribing to a socket using ng2-stomp-service:

this.fooSubscription = this.stomp.subscribe('/topic/foo', (res) => {
    console.log('do stuff with res');
});

Sometimes the connection is lost, and I see "Whoops! Connection is lost. Reconnecting..."

At that point, Stomp automatically re-connects, but it never re- subscribes so I can start receiving data again.

How do I re-subscribe after Stomp automatically re-establishes the connection, so I can start receiving data again?

Answer 1

Stomp Service try to reconnect when the onError method is called.

I resolved your problem overriding the onError method of the StompService class in my controller:

/**
 * Unsuccessfull connection to server
 */
public onError = (error: string ) => {

  console.error(`Error: ${error}`);

  // Check error and try reconnect
  if (error.indexOf('Lost connection') !== -1) {
    if(this.config.debug){
        console.log('Reconnecting...');
    }
    this.timer = setTimeout(() => {
        this.startConnect();
    }, this.config.recTimeout || 5000);
  }
}

with the following:

this.stompService.onError = (error: string) => {

      console.error(`Error: ${error}`);

      // Check error and try reconnect
      if (error.indexOf('Lost connection') !== -1) {
        console.log('Reconnecting...');
        this.timer = setTimeout(() => {

          this.stompService.startConnect().then(() => {

            // ADD HERE THE SUBSCRIPTIONS
            this.socketSubscription = this.stompService.subscribe('/topic/foo', this.response);

          }).catch(err => console.error('Connessione al socket non riuscita'));
        }, this.stompService.config.recTimeout || 5000);
      }
    }

adding the subscriptions into the startConnect().then() .

Answer 2

I'm still open to suggestions here, but for now, I wanted to share the way in which I am currently getting around this problem.

On the stomp object, I noticed there were several properties, including another object called stomp . In there, I found an object called subscriptions that has one property for each current subscriptions (named with the string 'sub-' followed by a number, representing the index of the subscriptions... so the first subscription is ' sub-0 '. All those properties get wiped out in the event of a re-connect, resulting in an empty object.

So in my code, all I do is (once per second) check to see if I need to re-subscribe by checking to see if that subscriptions property has any properties.

setInterval(() => {
if (this.stomp.status === 'CONNECTED' && !this.stomp.stomp.subscriptions['sub-0']) {
     this.reestablishSubscriptions();
}, 1000);    

reestablishSubscriptions() {
   this.mySubscription = this.stomp.subscribe('/topic/foo', (res) => {
       // do stuff with subscription responses
   }
   this.myOtherSubscription = this.stomp.subscribe('/topic/foo2', (res) => {
       // do stuff with subscription responses
   }
}

Yeah, it's ugly... but that's why I'm definitely still open to suggestions.