Work around Google evil .ics feeds

I've happily been using akonadi for my calendars, and yesterday I added an .ics feed export from Google, as a URL file source. It is a link in the form:

After doing that, I noticed that the fan in my laptop was on more often than usual, and I noticed that akonadi-server and postgres were running very often, and doing quite a lot of processing.

The evil

I investigated and realised that Google seems to be doing everything they can to make their ical feeds hard to sync against efficiently. This is the list of what I have observed Gmail doing to an unchanged ical feed:

This causes akonadi to download and reprocess the entire ical feed at every single poll, and I can't blame akonadi for doing it. In fact, Google is saying that there is a feed with several years worth of daily appointments that all keep being changed all the time.

The work-around

As a work-around, I have configured the akonadi source to point at a local file on disk, and I have written a script to update the file only if the .ics feed has actually changed.

Have a look at the script: I consider it far from trivial, since it needs to do a partial parsing of the .ics feed to throw away all the nondeterminism that Google pollutes it with.

The setup

The script needs to be run periodically, and I used it as an opportunity to try systemd user timers:

    $ cat ~/.config/systemd/user/update-ical-feeds.timer
    Description=Updates ical feeds every hour
    # Only run when on AC power

    # Run every hour
    # Run a minute after boot

    $ cat ~/.config/systemd/user/update-ical-feeds.service
    Description=Update ICal feeds

    # Use oneshot to prevent two updates being run in case the previous one
    # runs for more time than the timer interval

    $ systemctl --user start update-ical-feeds.timer
    $ systemctl --user list-timers
    NEXT                         LEFT       LAST                         PASSED UNIT                    ACTIVATES
    Wed 2015-03-25 22:19:54 CET  59min left Wed 2015-03-25 21:19:54 CET  2s ago update-ical-feeds.timer update-ical-feeds.service

    1 timers listed.
    Pass --all to see loaded but inactive timers, too.

To reload the configuration after editing: systemctl --user daemon-reload.

Further investigation

I wonder if ConditionACPower needs to be in the .timer or in the .service, since there is a [Unit] section is in both. Update: I have been told it can be in the .timer.

I also wonder if there is a way to have the timer trigger only when online. There is a and I do not know if it is applicable. I also do not know how to ask systemd if all the preconditions are currently met for a .service/.timer to run.

Finally, I especially wonder if it is worth hoping that Google will ever make their .ics feeds play nicely with calendar clients.