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.
Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Added more unit tests for kube-scheduler.
**What this PR does / why we need it**:
Added more unit tests for kube-scheduler.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
NONE
**Special notes for your reviewer**:
NONE
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 52723, 53271). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Apply algorithm in scheduler by feature gates.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: part of #42001
**Release note**:
```release-note
Apply algorithm in scheduler by feature gates.
```
Automatic merge from submit-queue (batch tested with PRs 51574, 51534, 49257, 44680, 48836)
update scheduler to return structured errors instead of process exit
The scheduler Run method returns an error that is properly handled at higher levels. Instead of existing the process, we should return the error and handle it at higher level logic to allow testing of error conditions and composition of commands. The changes are relatively minor.
@sjenning @aveshagarwal
Automatic merge from submit-queue (batch tested with PRs 49409, 49352, 49266, 48418)
Fix duplication in scheduler.
**What this PR does / why we need it**:
This fixes duplicate code in scheduler.
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #
No issue.
**Special notes for your reviewer**:
**Release note**:
```release-note
```
@kubernetes/sig-scheduling-pr-reviews @bsalamat
Automatic merge from submit-queue
word spell error
**What this PR does / why we need it**:
**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
```NONE
Previously, the scheduler created two separate list watchers. This
changes the scheduler to be able to leverage a shared informer, whether
passed in externally or spawned using the new in place method. This
removes the last use of a "special" informer in the codebase.
Allows someone wrapping the scheduler to use a shared informer if they
have more information avaliable.
Automatic merge from submit-queue
Scheduler configurator looks for a specific key in ConfigMap.Data
**What this PR does / why we need it**: Changes scheduler configurator to look for a specific key in ConfigMap.Data instead of the old logic which expected only one entry to exist in the map. The key is a constant whose value is "policy.cfg".
**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
```
Cao Shufeng