Subscriptions do not throw error on websocket failure

Describe the bug When subscribing to AppSync updates through AWS Amplify, undefined websocket errors do not invoke the error callback. If a websocket is unable to connect and returns undefined, an error is logged in the console but the subscription’s error callback is not invoked.

To Reproduce This occurs when the webapp is connected to a network that blocks or inhibits websocket connections, such as some proxies and corporate networks.

Expected behavior When an error occurs such as a network disconnection, the error callback should be invoked. Currently a network disconnection invokes the error callback but an undefined websocket connection does not.

Desktop:

• OS: Windows 7, Windows 10, and MacOS X
• Browser: Chrome 73, IE 11, and Edge 15

Smartphone:

• Device: iPhone X
• OS: iOS 12.2
• Browser: Safari

Sample code

API.graphql(
  graphqlOperation(subscriptions.mutatedItem, { item_id: item_id })
).subscribe({
  error: (err) => console.log("Network disconnected"),
  next: (eventData) => updateItems(eventData)
});

Console Output

paho-mqtt.js:1128 WebSocket connection to ‘wss://**************-ats.iot.us-west-2.amazonaws.com/mqtt?..’ failed: Error during WebSocket handshake: Unexpected response code: 400 S._doConnect @ paho-mqtt.js:1128

Uncaught (in promise) Object errorCode: 7 errorMessage: “AMQJS0007E Socket error:undefined.” invocationContext: undefined

[justinjoyn]

Any update on this? I always get this error when trying to subscribe to a topic after internet is restored.

     "errorCode":7,
     "errorMessage":"AMQJS0007E Socket error:undefined."

[borch84]

I let my application run for sometime and I watched messages console. Then I reloaded my web browser and I got this:

WARN] 12:06.456 MqttOverWSProvider - bd35da34-d348-44ae-8da7-31456c485019 {
  "errorCode": 8,
  "errorMessage": "AMQJS0008I Socket closed.",

I did not get the undefined socket error and the application still shows messages from the topic. It looks like the reconnection is happening internally. I wonder if it could useful that MqttOverWSProvider informs about any reconnection issue to the user?. Thanks.