Enable logrotate for Kubernetes configs on CoreOS

[julianvmodesto]

Addresses #2710.

Also, remove logrotate crontab because logrotate ships with a systemd timer, logrotate.timer, to run logrotate daily.

[k8s-ci-robot]

Hi @julianvmodesto. Thanks for your PR.

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[justinsb]

/ok-to-test

[chrislovecnm]

Question for you

[chrislovecnm]

How are we enabling? Confused ... sorry

[julianvmodesto]

Logrotate is already installed on CoreOS, so we don't need to install the package, only the logrotate conf.

https://github.com/coreos/init/blob/9b0971c8f7f1d634daa399b74f2591cac97f1ede/systemd/system/logrotate.service#L5

https://github.com/coreos/init/blob/9b0971c8f7f1d634daa399b74f2591cac97f1ede/configs/logrotate.conf#L18-L19

Would c.AddTask(&nodetasks.Package{Name: "logrotate"}) be okay to run away on CoreOS?

[chrislovecnm]

@julianvmodesto you can answer

Would c.AddTask(&nodetasks.Package{Name: "logrotate"}) be okay to run away on CoreOS?

Better than I :) What do you recommend? Test it

[justinsb]

No - you generally can't run the Package task on CoreOS - it'll complain that it doesn't know the package manager, because it only supports apt & yum.

[justinsb]

I'll take a look at this - thank you! It looks good, I just need to verify that the rotation is indeed installed on Debian, but it sounds right :-)

[justinsb]

/retest

was a testing problem, not a PR issue

[justinsb]

Thanks @julianvmodesto - will be great to get logrotation working on CoreOS!

Can we keep the hourly rotation, i.e. wrap that block in an if !coreOS statement? Because the logs do get big fast, so the recommendation is to rotate them hourly, and I'm pretty sure that in both jessie & stretch it's only configured to rotate daily (e.g. https://packages.debian.org/stretch/amd64/logrotate/filelist and https://stackoverflow.com/questions/25485047/hourly-rotation-of-files-using-logrotate).

I suspect we'll actually want to tweak CoreOS to logrotate more often than daily, but we can see :-) But I don't want to change the existing behaviour for Debian images.

[julianvmodesto]

Done!

Instead of an hourly cron, could we use an houry systemd timer for Jessie and CoreOS, the latter by overriding the existing timer?

https://github.com/coreos/init/blob/9b0971c8f7f1d634daa399b74f2591cac97f1ede/systemd/system/logrotate.timer

e.g.

	// Add timer to run hourly.
	unit := &systemd.Manifest{}
	unit.Set("Unit", "Description", "Hourly Log Rotation")
	unit.Set("Timer", "OnCalendar", "hourly")

	service := &nodetasks.Service{
		Name:       "logrotate.timer",
		Definition: s(unit.Render()),
	}

	service.InitDefaults()

	c.AddTask(service)

[justinsb]

/lgtm

thanks @julianvmodesto!

On the idea of moving to the hourly systemd timer, that would be great - we could even trigger it more often if needed than hourly. Want to send a PR? :-)

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[k8s-github-robot]

Automatic merge from submit-queue.