.info/connected does not change to false when offline

[hiranya911]

From firebase/firebase-admin-node#99

I've verified that this issue occurs with latest RTDB code as well (@firebase/database 0.1.2)

Environment

Debian buster
Node.js v 8.5.0
firebase-admin v ^5.0.0

Steps to reproduce:

1. Start application and wait for console log "Firebase connected!"
2. Go offline (switch off wifi or remove lan cable etc.)

When internet connection is disabled, application should print "Firebase disconnected".
It seems, it never does!

Relevant Code:

"use strict";

var path = require('path');
var admin = require("firebase-admin");

var serviceAccount = require(path.join(__dirname, "some-firebase-adminsdk-lu0x5-82c66d50f5.json"));

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: "https://some.firebaseio.com/"
});

const database = admin.database();

var connectedRef = database.ref(".info/connected");
connectedRef.on("value", function(snap) {
  if (snap.val() === true) {
    console.log("Firebase connected!");
  } else {
    console.log("Firebase disconnected!");
  }
});

[google-oss-bot]

Hey there! I couldn't figure out what this issue is about, so I've labeled it for a human to triage. Hang tight.

[google-oss-bot]

Hmmm this issue does not seem to follow the issue template. Make sure you provide all the required information.

[schmidt-sebastian]

Hiranya, do you know if this a Node only issue? Our networking layer is different in Node and I wonder whether this is something we never supported (it also doesn't make as much sense in Node as it does on the mobile platforms).

[mikelehen]

FWIW, I would expect it to work (the websocket connection should die and trigger .info/connected to change), but it may take a really long time (e.g. 15 minutes) depending on OS TCP timeout settings, etc.

[hiranya911]

I have only tested this in Node (with the Admin SDK). I think @mikelehen may be right. I remember seeing this event fire long time (> 15 mins) after a disconnect. Since the delay was long, I brushed it off as a fluke. I also agree that it is not a very popular use case for server-side environments. So may be we can just ensure it works in the web SDK, and document the behavior for Node?

[schmidt-sebastian]

It really depends on the underlying network stack. We have seen that this event doesn't fire for a full hour on some Android devices as the TCP retry window prevents the network stack from bubbling up these connection drops.

[kkm]

+1

[AndryBray]

I have the same after upgrading to 4.1.5 (https://firebase.google.com/support/release-notes/js) - previous versions where OK.
It's like the event is fired twice:

• first time offline
• second time online again (but this is wrong)

[gsushant]

As @AndryBray pointed out, I am having the same issue (event firing twice - offline followed by online). The example at: https://firebase.google.com/docs/database/web/offline-capabilities#section-presence works fine with 4.1.3 but doesn't work with 4.1.4 (and 5.0.4).