swarm1055-c4: It seems to be working now. It was rebooted (by someone?) at 11:13 and works fine since then. Before that puppet agent was stuck on the machine too, so it was likely in some unhealthy state...

build153-b1.labs had something happened to its Windows Task Scheduler, it stopped running tasks (this includes Puppet and luci_machine_tokend process that refreshes auth tokens for Swarming). I kicked it manually and rebooted the machine. Maybe it'll help... Nope, it didn't.

I think I know what's going on. Windows thinks the machine is running on battery power and disables scheduled tasks. There's a task property "Start the task only if the computer is on AC power", and by default it is ON. I flipped it to OFF, rebooted the machine and service_manager task started as it should (it didn't before). Also power icon in the tray is a battery, without charging indicator...

I modified 'puppet' and 'luci_machine_tokend' tasks manually for now.

Labs, is it expected that build153-b1 think it is running on battery power (and thus disables its scheduled tasks, including puppet)?

Filed issue 813784 to report power source, as I see this could be useful for self-health check; This is independent of making sure the task scheduler bit is set to run even when the host thinks it's running on battery.

Interesting.  It thinks it was running on battery power with the battery at 100%.   Reset the power supply connector at the laptop end and that tickled it's brain back to shape.