InitLogs overrides the klog default and turns contextual logging off. This
ensures that it is only enabled in Kubernetes commands that explicitly enable
it via a feature gate. A feature gate for it gets defined in
k8s.io/component-base/logs and is then used by Options.ValidateAndApply.
The effect of disabling contextual logging is very limited according to
benchmarks with kube-scheduler. The feature gets added anyway to satisfy the
PRR recommendation that features should be controllable.
The following commands have support for contextual logging:
- kube-apiserver
- kube-controller-manager
- kubelet
- kube-scheduler
- component-base/logs example
Supporting a feature gate check in ValidateAndApply and not in InitLogs is a
simplification: changing InitLogs to accept a FeatureGate would have implied
changing also component-base/cli.Run. This didn't seem worthwhile because
ValidateAndApply already covers the relevant commands.
In various places log messages where emitted as part of validation or even
before it (for example, cli.PrintFlags). Those log messages did not use the
final logging configuration, for example text output instead of JSON or not the
final verbosity. The last point became more obvious after moving the setup of
verbosity into logs.Options.Apply because PrintFlags never printed anything
anymore.
In order to force applications to deal with logging as soon as possible, the
Options.Validate and Options.Apply methods are now private. Applications should
use the new Options.ValidateAndApply directly after parsing.
These three options are the ones from logs.AddFlags which are not deprecated.
Therefore it makes sense to make them available also via the configuration file
support in the one command which currently supports that (kubelet).
Long-term, all commands should use LoggingConfiguration, either with a
configuration file (as in kubelet) or via flags (kube-scheduler,
kube-apiserver, kube-controller-manager).
Short-term, both approaches have to be supported. As the majority of the
commands only use logs.AddFlags, that function by default continues to register
the flags and only leaves that to Options.AddFlags when explicitly requested.
A drive-by bug fix is done for log flushing: the periodic flushing called
klog.Flush and therefore missed explicit flushing of the newer logr
backend. This bug was never present in any release Kubernetes and therefore the
fix is not submitted in a separate PR.
The new handler is meant to be executed at the end of the delegation chain.
It simply checks if the request have been made before the server has installed all known HTTP paths.
In that case it returns a 503 response otherwise it returns a 404.
We don't want to add additional checks to the readyz path as it might prevent fixing bricked clusters.
This specific handler is meant to "protect" requests that arrive before the paths and handlers are fully initialized.
When API Priority and Fairness is enabled, the inflight limits must
add up to something positive.
This rejects the configuration that prompted
https://github.com/kubernetes/kubernetes/issues/102885
Update help for max inflight flags
FeatureGate acts as a secondary switch to disable cloud-controller loops
in KCM, Kubelet and KAPI.
Provide comprehensive logging information to users, so they will be
guided in adoption of out-of-tree cloud provider implementation.
