Refactor the kube-scheduler configuration API, command setup, and server
setup according to the guidelines established in #32215 and using the
kube-proxy refactor (#34727) as a model of a well factored component
adhering to said guidelines.
* Config API: clarify meaning and use of algorithm source by replacing
modality derived from bools and string emptiness checks with an explicit
AlgorithmSource type hierarchy.
* Config API: consolidate client connection config with common structs.
* Config API: split and simplify healthz/metrics server configuration.
* Config API: clarify leader election configuration.
* Config API: improve defaulting.
* CLI: deprecate all flags except `--config`.
* CLI: port all flags to new config API.
* CLI: refactor to match kube-proxy Cobra command style.
* Server: refactor away configurator.go to clarify application wiring.
* Server: refactor to more clearly separate wiring/setup from running.
Fixes#52428.
Allow the list of resources the garbage collector controller should
ignore to be customizable, so downstream integrators can add their own
resources to the list, if necessary.
Automatic merge from submit-queue
Allow multipe DNS servers as comma-seperated argument for kubelet --dns
This PR explores how kubectls "--dns" could be extended to specify multiple DNS servers for in-cluster PODs. Testing on the local libvirt-coreos cluster shows that multiple DNS server are injected without issues.
Specifying multiple DNS servers increases resilience against
- Packet drops
- Single server failure
I am debugging services that do 50+ DNS requests for a single incoming interactive request, thus highly increase the chance of a slowdown (+5s) due to a single packet drop. Switching to two DNS servers will reduce the impact of the issues (roughly +1s on glibc, 0s on musl, error-rate goes down to error-rate^2).
Note that there is no need to change any runtime related code as far as I know. In the case of "default" dns the /etc/resolv.conf is parsed and multiple DNS server are send to the backend anyway. This only adds the same capability for the clusterFirst case.
I've heard from @thockin that multiple DNS entries are somehow considered. I've no idea what was considered, though. This is what I would like to see for our production use, though.
```release-note
NONE
```
Depending on an exact cluster setup multiple dns may make sense.
Comma-seperated lists of DNS server are quite common as DNS servers
are always plain IPs.
Automatic merge from submit-queue (batch tested with PRs 39469, 40557)
Forgiveness api changes
**What this PR does / why we need it**:
Splited from #34825 , contains api changes that are needed to implement forgiveness:
1. update toleration api types to support forgiveness, added a new field forgivenessSeconds to indicate the duration of time it tolerates a taint.
2. update taint api types, added a new field to indicate the time the taint is added.
**Which issue this PR fixes** :
Related issue: #1574
Related PR: #34825
**Special notes for your reviewer**:
**Release note**:
```release-note
forgiveness alpha version api definition
```
Automatic merge from submit-queue (batch tested with PRs 39807, 37505, 39844, 39525, 39109)
Admission control support for versioned configuration files
**What this PR does / why we need it**:
Today, the `--admission-control-config-file=` argument takes an opaque file that is shared across all admission controllers to provide configuration. This file is not well-versioned and it's shared across multiple plug-ins. Some plugins take file based configuration (`ImagePolicyWebhook`) and others abuse flags to provide configuration because we lacked a good example (`InitialResources`). This PR defines a versioned configuration format that we can use moving forward to provide configuration input to admission controllers that is well-versioned, and does not require the addition of new flags.
The sample configuration file would look as follows:
```
apiVersion: componentconfig/v1alpha1
kind: AdmissionConfiguration
plugins:
- name: "ImagePolicyWebhook"
path: "image-policy-webhook.json"
```
The general behavior is each plugin that requires additional configuration is enumerated by name. An alternate file location is provided for its specific configuration, or the configuration can be embedded as a raw extension via the configuration section.
**Special notes for your reviewer**:
A follow-on PR will be needed to make `ImagePolicyWebhook` to use versioned configuration. This PR maintains backwards compatibility by ignoring configuration it cannot understand and therefore treating the file as opaque. I plan to make use of this PR to complete https://github.com/kubernetes/kubernetes/pull/36765 which attempts to allow more configuration parameters to the `ResourceQuota` admission plugin.
Automatic merge from submit-queue (batch tested with PRs 39351, 39322)
Remove the deprecated --reconcile-cidr flag from kubelet
**What this PR does / why we need it**:
Removes the `--reconcile-cidr` flag that has been deprecated since v1.5
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
The `--reconcile-cidr` kubelet flag was removed since it had been deprecated since v1.5
```
@thockin
Provides an opt-in flag, --experimental-fail-swap-on (and corresponding
KubeletConfiguration value, ExperimentalFailSwapOn), which is false by default.
Automatic merge from submit-queue
make using service account credentials from controllers optional
Adds a flag to make the "SA per controller" behavior optional.
In order to be able to use new mounter library, this PR adds the
mounterPath flag to kubelet which passes the flag to the mount
interface. If flag is empty, mount uses default mount path.
