[Fixed] GraphQL Subscriptions: Max Listeners Exceeded Warning

[ayoubyoub]

Hi

When more than 11 subscriptions occur we get the the node warning "MaxListenersExceededWarning: Possible EventEmitter memory leak detected."

The subscription server looks like this:

const pubsub = new PostgresPubSub({
  host: 'localhost',
  port: process.env.DB_PORT ? parseInt(process.env.DB_PORT) : 5432,
  user: 'testuser',
  password: 'testpassword',
  database: 'whatsapp',
});

[Solution] So i found out that you can change the max listeners in the event emitter of the pubsub instance, like so:

const pubsub = new PostgresPubSub({
  host: 'localhost',
  port: process.env.DB_PORT ? parseInt(process.env.DB_PORT) : 5432,
  user: 'testuser',
  password: 'testpassword',
  database: 'whatsapp',
});

pubsub.ee.setMaxListeners(0); // raise max listeners in event emitter, 0 mean that is limited

Thanks for sharing.
Best regards,

[Urigo]

mmm maybe it's worth adding a note about running pub/sub in a separate process/engine?