Kubelet doesn't perform checkpointing and loses all its internal states after
restarts. It'd then mistaken pods from the api server as new pods and attempt
to go through the admission process. This may result in pods being rejected
even though they are running on the node (e.g., out of disk situation). This
change adds a condition to check whether the pod was seen before and categorize
such pods as updates. The change also removes freeze/unfreeze mechanism used to
work around such cases, since it is no longer needed and it stopped working
correctly ever since we switched to incremental updates.
There has been a recent regression causing kubelet to assume no containers are
running for the pod if kubelet has not seen the pod before. This would cause
all containers to be restarted after kubelet gets restarted. This change fixes
the bug.
Implement a flag that defines the frequency at which a node's out of
disk condition can change its status. Use this flag to suspend out of
disk status changes in the time period specified by the flag, after
the status is changed once.
Set the flag to 0 in e2e tests so that we can predictably test out of
disk node condition.
Also, use util.Clock interface for all time related functionality in
the kubelet. Calling time functions in unversioned package or time
package such as unversioned.Now() or time.Now() makes it really hard
to test such code. It also makes the tests flaky and sometimes
unnecessarily slow due to time.Sleep() calls used to simulate the
time elapsed. So use util.Clock interface instead which can be faked
in the tests.
Refactor Kubelet's server functionality into a server package. Most
notably, move pkg/kubelet/server.go into
pkg/kubelet/server/server.go. This will lead to better separation of
concerns and a more readable code hierarchy.
The formatting function is used often in logging. This improves the readability
by shortening the length of the call. Also change the fomartted string to
include the pod UID.
Before this change we have a mish-mash of ways to pass field names around for
error generation. Sometimes string fieldnames, sometimes .Prefix(), sometimes
neither, often wrong names or not indexed when it should be.
Instead of that mess, this is part one of a couple of commits that will make it
more strongly typed and hopefully encourage correct behavior. At least you
will have to think about field names, which is better than nothing.
It turned out to be really hard to do this incrementally.
