Checking for updates never finishes on 3G when no updates available

[Anupam]

If I'm using wi-fi and go to settings and then select updates, "Checking for updates..." screen appears with a spinner for a few seconds; if there is any update available it shows, otherwise informs about the unavailability of updates.
But while using mobile data (3G/H) *if there is no update available*, it gets stuck on the "Checking for updates..." screen and the spinner keeps spinning. I waited as long as 10-15 minutes.
Note: If there is an update available then the behaviour is normal, i.e. shows the available update(s) after a few seconds.
I'm seeing this behaviour from the very beginning (OTA-6 days).

Related to bug #1528886

UPDATE: It's gotten weirder after the introduction of the new update panel in OTA-13. When there is an update available, it keeps on "Checking for updates..." along with the list of available updates:
https://launchpadlibrarian.net/297883544/screenshot20161212_215042136.png

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Pat McGowan (pat-mcgowan)]

Seems the fix from the referenced bug regressed

[Pat McGowan (pat-mcgowan)]

I was not able to reproduce it, perhaps the cellular data connection is not really active?

[Anupam (anupam207)]

@Pat just tried this once again, it actually took 9-10 minutes to show "Software is up to date" on 3G (started at 17:23, showed at around 17:33). Maybe something to do with the data connection! But I noticed earlier, if there are updates available, it lists them after 2-3 seconds on the same data connection. Also before and after this update check I opened browser, facebook app, hangups app etc. All are working fine, not super slow or something like that.

[Pat McGowan (pat-mcgowan)]

I reproduced one case where there was an update available but something may have failed during the download so the UI got into a confused state with several different symptoms, the first was to get stuck on the spinner indefinitely. Renetering the panel showed an already downloaded system update.

So perhaps just generally racy logic. There is a rewrite of this panel in progress to address similar symptoms.

[Pat McGowan (pat-mcgowan)]

@anupam what is your auto download setting?

[Anupam (anupam207)]

@Pat wi-fi only

[Pat McGowan (pat-mcgowan)]

I managed to repro it at 16:09 and 16:19 in the following log from system-image. I got it both with download anytime and download wifi only so that seems to not be related.

After 10 mins system-image reported a timeout error which resulted in "Software is up to date" while a timeout error should really be reported in the UI.

[Pat McGowan (pat-mcgowan)]

Set auto download to never (which is how I usually set it) rebooted and it worked fine on 3G
Set back to on wifi and it hung.

[Pat McGowan (pat-mcgowan)]

@barry any more steps we can do to debug

[Jonas G. Drange (jonas-drange)]

Can reproduce this on the rewrite.

Seems to hang in s-i [1], whereas the UDM group download finishes [2]?

However, with the new panel I can cancel the check and successfully start a new one. Not sure if this is new, but recovery is possible.

[1] http://pastebin.ubuntu.com/23117265/
[2] http://pastebin.ubuntu.com/23117272/

[Jonas G. Drange (jonas-drange)]

Marked this bug as incomplete for System Settings as it's not clear to me that System Image tells System Settings that it has finished checking (i.e. timed out if that's the case). We need some sort of signal in these cases.

[Víctor R. Ruiz (vrruiz)]

I was able to reproduce this with wifi. Checking updates takes a long time to finish. The panel thinks that a check was already in progress: http://paste.ubuntu.com/23136927/