Useless pushes with no changes sent when reading rooms with no notifs enabled

[MatMaul]

Description

Duplicate pushes are sent whenever you read a room, even if notifications are disabled for this room and there is no change in the notifs count.

Steps to reproduce

• read a room with no notifs (read receipt is sent)
• a push is sent, identical to the previous push, with no event_id/room_id and an unchanged count

This is annoying for big accounts that are also extensively used on a computer device, because the phone basically never sleeps.

[reivilibre]

I can see this being pretty bad because the excessive push traffic is bad for the app's 'reputation' essentially, on modern phone operating systems, resulting in pushes getting throttled.

A potential fix seems to be fairly simple:

• update HttpPusher to add a field to keep track of the last sent badge count
• in HttpPusher._update_badge, don't do anything if the count hasn't changed (and store the last-sent unread count)

[lukasdenk]

I'll work on it.

[lukasdenk]

@reivilibre Are you sure about your potential fix?
I have set a break point into the HttpPusher_update_badge and its callee, on_new_receipts. Everything worked but synapse never came to the breakpoints.

I tried the following setting:

• setup a homeserver with default settings
• started two Element clients (both on ubuntu)
• created public rooms 1 and 2 with user A.
• Joined rooms 1 and 2 with user B.
• Send messages from user A to B and vice versa

[reivilibre]

@lukasdenk I suppose I can't say I'm sure until it's actually proven.
However I think your problem is that your Element Web/Desktop clients won't be using a push gateway — you'd have to use a mobile client like Element Android/iOS or FluffyChat etc.
(It might be possible to use Web Push with the Hydrogen client which runs in a browser, but I haven't been keeping track so I'm not certain.)

If I was doing this, I would say that it would probably be easiest to first write a failing test for this situation described by MatMaul.
Now you can use breakpoints as you please, and you don't have to test it all manually with a real push gateway.
When you fix the issue, you even get a test included to ensure it keeps working afterwards! :)
(test_push_unread_count_message_count in tests.push.test_http is probably one of the closest tests you can refer to, for inspiration when writing your own test.)

[himanshi-2602]

@lukasdenk are you still working on this issue?
@reivilibre can I work on this issue?
I am a beginner but I am really interested in open source

[lukasdenk]

@himanshi-2602 Yes, I am