Apply a small fix to ensure the kubeconfig files
that kubeadm manages have a CA when printed in the table
of the "check expiration" command. "CAName" is the field used for that.
In practice kubeconfig files can contain multiple credentials
from different CAs, but this is not supported by kubeadm and there
is a single cluster CA that signs the single client cert/key
in kubeadm managed kubeconfigs.
In case stacked etcd is used, the code that does expiration checks
does not validate if the etcd CA is "external" (missing key)
and if the etcd CA signed certificates are valid.
Add a new function UsingExternalEtcdCA() similar to existing functions
for the cluster CA and front-proxy CA, that performs the checks for
missing etcd CA key and certificate validity.
This function only runs for stacked etcd, since if etcd is external
kubeadm does not track any certs signed by that etcd CA.
This fixes a bug where the etcd CA will be reported as local even
if the etcd/ca.key is missing during "certs check-expiration".
When the "kubeadm certs check-expiration" command is used and
if the ca.key is not present, regular on disk certificate reads
pass fine, but fail for kubeconfig files. The reason for the
failure is that reading of kubeconfig files currently
requires reading both the CA key and cert from disk. Reading the CA
is done to ensure that the CA cert in the kubeconfig is not out of date
during renewal.
Instead of requiring both a CA key and cert to be read, only read
the CA cert from disk, as only the cert is needed for kubeconfig files.
This fixes printing the cert expiration table even if the ca.key
is missing on a host (i.e. the CA is considered external).
If done too soon, the klog.V() calls are ignored because the log verbosity
isn't set. In Kubernetes 1.22, the verbosity was set, but not the logging
format.
Don't use a custom dialer for the kubelet if is not rotating
certificates, so we can reuse TCP connections because we don't need
a customer dialer.
Kubelet needs to be able to recover from stale http connections.
HTTP2 has a mechanism to detect broken connections by sending periodical pings.
HTTP1 only can have one persistent connection, and it will close all Idle connections
once the Kubelet heartbet fails. However, since there are many edge cases that we can't
control, users can still opt-in to the previous behavior for closing the connections by
setting the environment variable DISABLE_HTTP2.
