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apiserver clean code
**What this PR does / why we need it**:
1. clean up some redundant code in kube-apiserver startup
1. comment on `preparedGenericAPIServer`, which is just a wrapper of `GenericAPIServer`.
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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implement begin-port+offset port range parsing
**What this PR does / why we need it**:
Allocate specific numbers of port from a host by indicating a begin port and its offsets.
This can be used for kube-proxy configuration.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#58730
**Special notes for your reviewer**:
**Release note**:
```release-note
"beginPort+offset" format support for port range which affects kube-proxy only
```
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more concise to merge the slice
**What this PR does / why we need it**:
more concise to merge the slice
**Special notes for your reviewer**:
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prevent the same path load multiple times
**What this PR does / why we need it**:
prevent the same path load multiple times，if there are several same path, we only load one time
**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes#53723
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 60737, 60739, 61080, 60968, 60951). 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>.
Fix default auditing options.
- Log backend defaults to blocking mode (backwards compatability)
- Webhook backend defaults to throttled
- Fix webhook validation
- Add options test
**Which issue(s) this PR fixes**:
Fixes#60719
**Special notes for your reviewer**:
This PR is an alternative fix to https://github.com/kubernetes/kubernetes/pull/60727. If the rollback goes in first, I'll rebase this on a roll-forward.
**Release note**:
-->
```release-note
NONE
```
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Bump to etcd 3.1.12 to pick up critical fix
etcd [3.1.12](https://github.com/coreos/etcd/releases/tag/v3.1.12) (as well as 3.2.17 and 3.3.2) was released yesterday to fix a bug critical to kubernetes:
Fix [mvcc "unsynced" watcher restore operation](https://github.com/coreos/etcd/pull/9297).
- "unsynced" watcher is watcher that needs to be in sync with events that have happened.
- That is, "unsynced" watcher is the slow watcher that was requested on old revision.
- "unsynced" watcher restore operation was not correctly populating its underlying watcher group.
- Which possibly causes [missing events from "unsynced" watchers](https://github.com/coreos/etcd/issues/9086).
This will be backported to 1.9 as well.
Release note:
```release-note
Upgrade the default etcd server version to 3.1.12 to pick up critical etcd "mvcc "unsynced" watcher restore operation" fix.
```
cc @gyuho @wojtek-t @shyamjvs @timothysc @jdumars
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fix option --audit-webhook-initial-backoff
Before this change, --audit-webhook-initial-backoff has no effect
@crassirostris @sttts
**What this PR does / why we need it**:
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
Created a scheme that only understands admission/v1beta1 and use it to
encode/decode admissionReviews.
Also made the NegotiationSerializer setup static
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Make admission webhooks honor scheme part of url
**What this PR does / why we need it**:
Bug fix, allow webhooks to use the scheme provided in clientConfig, instead of defaulting to http.
(more in issue)
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#60942
```release-note
Bug fix, allow webhooks to use the scheme provided in clientConfig, instead of defaulting to http.
```
/kind bug
/sig api-machinery
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Rollback etcd server version to 3.1.11 due to #60589
Ref https://github.com/kubernetes/kubernetes/issues/60589#issuecomment-371171837
The dependencies were a bit complex (so many things relying on it) + the version was updated to 3.2.16 on top of the original bump.
So I had to mostly make manual reverting changes on a case-by-case basis - so likely to have errors :)
/cc @wojtek-t @jpbetz
```release-note
Downgrade default etcd server version to 3.1.11 due to #60589
```
(I'm not sure if we should instead remove release-notes of the original PRs)
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update Mount propagation version in comment
**What this PR does / why we need it**:
Mount propagation feature was moved to beta in PR [#59252](https://github.com/kubernetes/kubernetes/pull/59252)， so update the comment.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes#60657
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
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log enabled admission controller in order
After switching to --enable-admission-plugins/--disable-admission-plugins, some admission controller may start silently. And these admission controllers may modify or forbid objects. This pull request does a lot of help for admin to trouble shooting.
/assign @hzxuzhonghu @sttts
**Release note**:
```release-note
NONE
```
