Add test coverage to the certificate manager covering the initialization
scenario where it is initialized with no Certificate Request Signing
client, then the client is added later. This matches how it will be used
when the Certificate Request Signing client is also the consumer of the
certificate manager.
Adds support to the certificate manager so it can be initialized with no
certs and only a connection to the certificate request signing API. This
specifically covers the scenario for the kubelet server certificate,
where there is a request signing client but on first boot there is no
bootstrapping or local certs.
Automatic merge from submit-queue (batch tested with PRs 44364, 44361, 42498)
Fix the certificate rotation threshold and add jitter.
Adjusts the certificate rotation threshold to be fixed, with some jitter to
spread out the load on the Certificate Signing Request API. The rotation
threshold is fixed at 20% now, meaning when 20% of the certificate's total
duration is remaining, the certificate manager will attempt to rotate, with
jitter +/-10%. For certificates of duration 1 month that means they will
rotate after 24 days, +/- 3 days.
On a 6000 node cluster, assuming all nodes added at nearly the same time, this
should result in 6000 nodes rotating spread over 6 days (total range of the
jitter), or ~42 nodes / hour requesting new certificates.
Changes the kubelet so it doesn't use the cert/key files directly for
starting the TLS server. Instead the TLS server reads the cert/key from
the new CertificateManager component, which is responsible for
requesting new certificates from the Certificate Signing Request API on
the API Server.
Jacob Simpson