nixos/waybar: restart service

[erictapen]

Motivation for this change

Waybar sometimes fails, especially when sway is being started. This should circumvent some headaches.

Things done

Restart waybar automatically after 5 seconds.

Related: #57602

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

Notify maintainers

cc @FlorianFranzen @minijackson @Synthetica9

[minijackson]

I haven't tried it yet, but it seems fine and pretty useful to me!

[ghost]

What's the root cause of the failure? I would prefer to solve it upstream than restarting and hoping for the best.

[erictapen]

I haven't identified a single root cause yet. But I observe my waybar sometimes restarting when I change display configuration via kanshi and when sway starts up.

I also think it is best practice to have this kind of service restart automatically. There is no good reason to stop waybar while sway is running and if people still want it for some reason, they can override it.

[FlorianFranzen]

@doom3wasagoodgame Waybar still has known bugs that can lead to crashes e.g. Alexays/Waybar#487, Alexays/Waybar#481 and Alexays/Waybar#433.

I would remove the RestartSec = 5 completely as there is no need to wait that long (the default is 100ms). By default the start rate limit stops any restarts that exceed 5 attempt per 10 seconds.

I think a Restart = "on-abnormal" would also be more in our interest, because that is really the case we want to fix here (see man systemd.service 5 for details). Otherwise this change will also restart the bar multiple times on shutdown through clean signals as well as when returning clean or unclean exit codes, e.g. when the config is invalid.

[erictapen]

@FlorianFranzen Thanks for the hint. I discovered that my waybar doesn't come up when I restart on-abnormal so I changed it back to always. At the moment it fails at first start with

Jan 20 15:31:32 maschine systemd[1616]: Started Waybar as systemd service.
Jan 20 15:31:32 maschine waybar[1637]: cannot open display: 
Jan 20 15:31:32 maschine systemd[1616]: waybar.service: Main process exited, code=exited, status=1/FAILURE
Jan 20 15:31:32 maschine systemd[1616]: waybar.service: Failed with result 'exit-code'.

Otherwise this change will also restart the bar multiple times on shutdown through clean signals as well as when returning clean or unclean exit codes, e.g. when the config is invalid.

That's not something I observed at least. Anyway I think its safer atm to restart it more often than less often.

Regarding RestartSec: I use the default value now.

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[erictapen]

I stopped using Waybar, so I don't really care anymore.