Making the LoggingConfiguration part of the versioned component-base/config API
had the theoretic advantage that components could have offered different
configuration APIs with experimental features limited to alpha versions (for
example, sanitization offered only in a v1alpha1.KubeletConfiguration). Some
components could have decided to only use stable logging options.
In practice, this wasn't done. Furthermore, we don't want different components
to make different choices regarding which logging features they offer to
users. It should always be the same everywhere, for the sake of consistency.
This can be achieved with a saner Go API by dropping the distinction between
internal and external LoggingConfiguration types. Different stability levels of
indidividual fields have to be covered by documentation (done) and potentially
feature gates (not currently done).
Advantages:
- everything related to logging is under component-base/logs;
previously this was scattered across different packages and
different files under "logs" (why some code was in logs/config.go
vs. logs/options.go vs. logs/logs.go always confused me again
and again when coming back to the code):
- long-term config and command line API are clearly separated
into the "api" package underneath that
- logs/logs.go itself only deals with legacy global flags and
logging configuration
- removal of separate Go APIs like logs.BindLoggingFlags and
logs.Options
- LogRegistry becomes an implementation detail, with less code
and less exported functionality (only registration needs to
be exported, querying is internal)
- Change the feature gate from alpha to beta and enable it by default
- Update a few of the unit tests due to feature gate being enabled by
default
- Small refactor in `nodeshutdown_manager` which adds `featureEnabled`
function (which checks that feature gate and that
`kubeletConfig.ShutdownGracePeriod > 0`).
- Use `featureEnabled()` to exit early from shutdown manager in the case
that the feature is disabled
- Update kubelet config defaulting to be explicit that
`ShutdownGracePeriod` and `ShutdownGracePeriodCriticalPods` default to
zero and update the godoc comments.
- Update defaults and add featureGate tag in api config godoc.
With this feature now in beta and the feature gate enabled by default,
to enable graceful shutdown all that will be required is to configure
`ShutdownGracePeriod` and `ShutdownGracePeriodCriticalPods` in the
kubelet config. If not configured, they will be defaulted to zero, and
graceful shutdown will effectively be disabled.
Implements KEP 2000, Graceful Node Shutdown:
https://github.com/kubernetes/enhancements/tree/master/keps/sig-node/2000-graceful-node-shutdown
* Add new FeatureGate `GracefulNodeShutdown` to control
enabling/disabling the feature
* Add two new KubeletConfiguration options
* `ShutdownGracePeriod` and `ShutdownGracePeriodCriticalPods`
* Add new package, `nodeshutdown` that implements the Node shutdown
manager
* The node shutdown manager uses the systemd inhibit package, to
create an system inhibitor, monitor for node shutdown events, and
gracefully terminate pods upon a node shutdown.
Nit: remove capitalization of preferred
Remove line from kubelet and add to separate PR for easier merge
nit: dependency added to separate PR
Add check to ensure strict policy cannot be set without feature gate enabled
Topology Manager runs "none" policy by default.
Added constants for policies and updated documentation.
