Defer snapd refresh on wake from suspend

snapd
1

As I understand it we now defer snapd refreshing snaps until some hours after a system has booted.

We do not appear to defer snapd refreshes after waking from suspend.

I tend to leave my laptop on and just suspend it by shutting the lid. It can go for a day or more without being opened. I have a lot (80+) of snaps installed, some of which are from the non-stable channels. So I get a fair number of updates on a frequent basis.

When I wake my laptop snapd will start refreshing all those snaps which helps to grind the machine to a halt for the first few minutes after waking. Snapd refreshing is contending with applications which are updating / sending notifications and unattended-upgrades.

Most recently wanted to wake my laptop up to do a ā€œquick bit of workā€ but was left waiting while snapd refreshed 7 applications (including core). I managed to get to a terminal and spotted snapd at the top of the list. This seems sub-optimal and inconsistent with our boot behaviour. Can we defer snapd refresh until some time after wake from suspend please?

5 Likes
2

Amy chance someone can take a look at this? @mvo maybe? :slight_smile:

3

I had this happen again today. My (16GB / i7 / SSD) laptop is completely unusable for minutes after waking from suspend as itā€™s doing all the snap refresh updates. Today there were only 8, but thatā€™s because I used my laptop yesterday. It can be way more, and thus more of a grind.

@niemeyer is this something we can please fix?

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4

@popey if instead of delaying the update, it was rate limited, would that work for you?

alternatively: I wonder if thereā€™s a straightforward way for systemd to stop snapd over suspend.

5

Hard to know if that will fix it without testing. Itā€™s not so much the network download which pegs my laptop. I believe itā€™s all the disk IO when copying files about. Itā€™s hard to know because the laptop is pegged and unusable during those operations.

6

What do you mean youā€™re not psychic?!

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7

We can add a Conflcits: sleep.target to snapd.service, but Iā€™m not sure how to bring it back up on resume.

We could also add a thing (something something systemd-sleep.conf something) so that we do a refresh hold on suspend, maybe thatā€™s easier.

8

Just had it again with 10 snaps refreshing on wake from suspend. It made video calls impossible until theyā€™d finished :frowning:

9

Instead of just the delay, it might be useful to ā€œrate limitā€ the number of snaps that get updated every X amount of minutes.

Say it wakes up, notices that 25 snaps need to be updated. Itā€™ll update 5 snaps every 10 minutes, spanning 50 minutes, giving priority to any core snaps. :man_shrugging:

10

Restart a snap background service on resume from suspend triggered some interest in addressing the problem of delaying snapd refresh on wakeup.

Since we now have the refresh.hoild functionality, Iā€™m playing with this little service locally:

[Unit]
Description=Hold snapd refresh when resuming from sleep
After=systemd-suspend.service systemd-hybrid-sleep.service systemd-hibernate.service

[Service]
Type=simple
ExecStart=/bin/sh -c '/usr/bin/snap set system refresh.hold=$(date --iso-8601=seconds -d "10 minutes")'

[Install]
WantedBy=sleep.target

The service should be run as part of sleep.target, but it will only be started after systemd helper services complete. The helpers implement the actual suspend/hibernate, and exit when the system wakes up, so snapd hold service should run right after.

Iā€™m testing this locally on Arch, with systemd 240. So far, across a couple of suspend/wakup cycles, the refresh-hold helper was being correctly started after the the system woke up and snapd configuration was updated accordingly.

Would you mind testing this for a while in your system? Write the unit definition to /etc/systemd/system/snapd.hold-refresh-after-resume.service and then execute:

$ systemctl daemon-reload && \
    systemctl enable snapd.hold-refresh-after-resume.service

Once the system resumes, there should be a log in the journal from when systemd started the service. The configuration of snapd should also be updated:

$ snap get system refresh
Key              Value
refresh.hold     2019-01-17T13:49:07+01:00   <--- this should be roughly
                                                  ~now + 10 minutes
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11

Thanks @mborzecki - Iā€™ve set that on my laptop and sure enough refresh.hold is 10 mins from now (after waking). Thanks.

12

Itā€™s 7 days into the field test. Have you noticed any issues so far?

13

Nope. Iā€™ve used my laptop with suspend a fair amount, and itā€™s certainly not felt bogged down when waking from suspend as it previously did. Thanks!

14

Opened a PR to snapd so that it doesnā€™t get lost: https://github.com/snapcore/snapd/pull/6438

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