/test pull-kubernetes-node-e2e

@mattjmcnaughton
Please take another look.

/test pull-kubernetes-e2e-gce-100-performance

/assign @MrHohn

/priority important-soon

Is this check just informational, for debugging purposes?

@tallclair
Since the log is not at error level, I would think so.

/approve

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/test pull-kubernetes-integration

I am not sure this really improved anything.

If network manager is restarted or the kubelet has a race with network manager, its possible the contents of /etc/resolv.conf could change underneath us. I preferred checking the contents of the file in the iteration loop rather than checking it once for the life of the process. It makes changes are harder to debug if/when there are actual problems.

I am fine with checking /etc/resolv.conf more than once.
I doubt whether the check should be done for every iteration though.
How about checking the contents every hour (open to suggestion on the duration) ?

	if start.Sub(kl.lastResolvConfCheck) > time.Hour {
		if kl.dnsConfigurer != nil && kl.dnsConfigurer.ResolverConfig != "" {
			kl.dnsConfigurer.CheckLimitsForResolvConf()
		}
		kl.lastResolvConfCheck = start
	}

where

	// lastResolvConfCheck records the time of last /etc/resolv.conf check
	lastResolvConfCheck time.Time

Currently the check logs a warning.
If at T1 the check passes and at T2 (> T1) the check fails, we should log an error.

@tedyu that makes sense.

Here is skeleton of proposed change for CheckLimitsForResolvConf (showing only one of the 4 klog's):

func (c *Configurer) CheckLimitsForResolvConf(sawGoodResolvConf bool) bool {

...
	_, hostSearch, _, err := parseResolvConf(f)
	if err != nil {
		c.recorder.Event(c.nodeRef, v1.EventTypeWarning, "CheckLimitsForResolvConf", err.Error())
		if sawGoodResolvConf {
			klog.Errorf("CheckLimitsForResolvConf: " + err.Error())
		} else {
			klog.V(4).Infof("CheckLimitsForResolvConf: " + err.Error())
		}
		return false
	}

@derekwaynecarr
If you think the above looks good, I will send out a PR.