Pkg.jl: opt-in precompilation after Pkg.update when laptop is on battery

[johnnychen94]

It's not very nice if your laptop is on battery and you happen to do a up, which I regularly do a lot. To keep the battery last longer, some of the precompilation can be done lazily until you actually need that.

Probably there should be a nice way to make this opt-in when the laptop is on battery.

[IanButterworth]

A single Ctrl-C will gracefully exit auto precompilation after a short wait (I've just added a message to reassure that it is exiting in #2113)

Otherwise, I'm not sure julia can know if the system is running on battery?

[Keno]

Otherwise, I'm not sure julia can know if the system is running on battery?

All the OSes have APIs for this

[fredrikekre]

Seems like a pretty strange thing to do IMO.

[IanButterworth]

@johnnychen94 you might want to just set ENV["JULIA_PKG_PRECOMPILE_AUTO"]=0 and just call pkg> precompile when you want it

It's also worth saying that while 1.6 isn't released, for people working on master a lot of stuff is going to get precompiled again and again as the master commit changes.. Once 1.6 is released, it will be a lot more stable

[johnnychen94]

Precompilation does not always happen in an interactive mode, for example, it can be background cronjob that updates packages in the root project. But I guess I'll live with Ctrl-C.

Yeah, I'm aware of the JULIA_PKG_PRECOMPILE_AUTO mode, and I have regularly switched between two modes because I both like the new precompilation feature and want to make my laptop working a bit longer when it's on battery. I don't have an expectation of what should be the best option here. Probably this is not a Julia Pkg thing and probably the best option is just to set a watchdog daemon to automate the switches.

[IanButterworth]

@johnnychen94 I knocked together https://github.com/ianshmean/PowerMonitor.jl which provides the following that can be added to .julia/config/startup.jl to disable auto-precomp when on battery.

import PowerMonitor
PowerMonitor.autoprecomp_notbattery()

I've only tested it on MacOS, but linux _should_ be supported.
I'm sure the code and function names could be nicer. PR's welcome!

[johnnychen94]

This looks really nice and clean! Sounds like a better place than Pkg to give it an implementation so I'll close it here.

Thanks again for all the parallel precompilation work!

[IanButterworth]

Through the wonders of JLLs, this is now fully cross-platform https://github.com/ianshmean/PowerMonitor.jl