e2e key backup takes forever

[turt2live]

I've been here for about 5 minutes and it still isn't done. A progress bar might help to show that the thing isn't dead?

[turt2live]

or run it async and tell me that it failed/succeeded later. It's not fun not being able to use riot for this long

[jryans]

I asked @turt2live to run a small script that logs the number of group sessions in the crypto store (assuming that a large number would be the main thing to cause backup to take a long time). His device has approximately 3x the number of group sessions that I am seeing, and for me backup is pretty fast, so it doesn't seem to explain the whole story here.

I suspect this might have become much faster after this issue opened: a few days after this issue was filed, we changed the keys sent per upload request from 10 to 200 (a 20x change). It's possible this greatly improved the key upload experience.

I have asked @turt2live to try again when he has time available.

[jryans]

@turt2live is still seeing delays of 5 - 10 minutes to create a key backup. Even if we can improve, I think we still want an async flow that uploads in the background.

[jryans]

Related: #8047

[jryans]

In my testing, it seems like the uploading step is the longest part of the process. For example, sending a batch of 200 keys (158 KiB of data) to the matrix.org HS took 2 - 3.5 seconds. With lots of keys to backup (@turt2live had around 3,000 on one device), it could easily take several minutes just for the upload portion (which would be highly network and server load dependent).