Automatic merge from submit-queue

Check existence of kubernetes dir for get-kube.sh

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There are a lot of references to https://get.k8s.io/ over the internet.
Most of such references do not describe KUBERNETES_SKIP_DOWNLOAD env variable
and newbies can get into a situation described below:

- execute `wget -q -O - https://get.k8s.io | bash`
- receive a failure due too missed packages or some configs
- fix the issue
- try again `wget -q -O - https://get.k8s.io | bash`

In this case, get-kube.sh will not check that kubernetes directory already
exist and repeat download again.
Lets make get-kube.sh more user-friendly and check existence of kubernetes dir

Automatic merge from submit-queue

Migrate most of the remaining integration tests to run in dedicated namespace (when possible).

Automatic merge from submit-queue

Fix node e2e issues on selinux enabled systems

It fixes following 3 node e2es:

```
[Fail] [k8s.io] Container Runtime Conformance Test container runtime conformance blackbox test when starting a container that exits [It] it should run with the expected status [Conformance] 
/root/upstream-code/gocode/src/k8s.io/kubernetes/test/e2e_node/runtime_conformance_test.go:114

[Fail] [k8s.io] Kubelet metrics api when querying /stats/summary [It] it should report resource usage through the stats api 
/root/upstream-code/gocode/src/k8s.io/kubernetes/test/e2e_node/kubelet_test.go:158
```
```
[Fail] [k8s.io] Container Runtime Conformance Test container runtime conformance blackbox test when starting a container that exits [It] should report termination message if TerminationMessagePath is set [Conformance]
/root/upstream-code/gocode/src/k8s.io/kubernetes/test/e2e_node/runtime_conformance_test.go:150
```
@kubernetes/rh-cluster-infra 

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allow handler to join after the informer has started

This allows an event handler to join after a SharedInformer has started.  It can't add any indexes, but it can add its reaction functions.

This works by 
 1. stopping the flow of events from the reflector (thus stopping updates to our store)
 1. registering the new handler
 1. sending synthetic "add" events to the new handler only
 1. unblocking the flow of events

It would be possible to 
 1. block
 1. list
 1. add recorder
 1. unblock
 1. play list to as-yet unregistered handler
 1. block
 1. remove recorder
 1. play recording
 1. add new handler
 1. unblock

But that is considerably more complicated.  I'd rather not start there since this ought to be the exception rather than the rule.

@wojtek-t who requested this power in the initial review
@smarterclayton @liggitt I think this resolves our all-in-one ordering problem.
@hongchaodeng since this came up on the call

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"Mover" should be "Moreover"

In file docs/proposals/apiserver-watch.md, line #108, "Mover, this will not require any changes in other parts of the code.", here "Mover" should be "Moreover".

Automatic merge from submit-queue

dedup workqueue requeuing

Updates `workqueue.AddAfter` to only perform the add for the earliest requested requeue operation.  An earlier time inserts in the earlier slot and removes the old one.  A later time is ignored.

When using this conjunction with an `AddRateLimited` method, you get charged for the additional retry even though you're only queue once.  

This keeps requeues from multiplying for every add.

@liggitt 

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ObjectReflectDiff has an incorrect array index comparison

Is comparing the wrong field for bounds.

@deads2k

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Add command "kubectl config get-contexts"

```release-note
* A new command "kubectl config get-contexts" has been added.
```

fixes #25383

Automatic merge from submit-queue

Migrate some integration tests to run in dedicated namespace.

Note: Context is not a runtime object (doesn't have Kind and Version) so
      we can't use the resource_printer

Automatic merge from submit-queue

Fix logic of consecutive DELETE calls when gracefull deletion is enabled

Previously it was possible to extend delete timestamp to infinity by issuing repeated DELETE calls. This PR prevents that. Ref. discussion in #27422

cc @wojtek-t @smarterclayton @lavalamp @piosz @dchen1107 

Automatic merge from submit-queue

cacher: replace usable lock with conditional variable

Perviously we use a rwlock to indicate the ready information of the cacher. I feel it is not straightforward. Also it requires a few comments to explain. The pull request tries to replace the lock with a conditional variable for readability reason.

/cc @lavalamp @wojtek-t   

Automatic merge from submit-queue

Handle more cases in diff.ObjectReflectDiff

Interfaces and nested map values were not being recursed.

@karkagis since @wojtek-t is out

Interfaces and nested map values were not being recursed.

Automatic merge from submit-queue

e2e: increase timeout when waiting for deployment pods to be deleted

Use the same timeout as the one used for waiting for the deployment
reaper to complete.

Takes a stab at https://github.com/kubernetes/kubernetes/issues/28067

@kubernetes/deployment  PTAL

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Simplify registries initialization

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Increase timeouts in multiple node pool e2e tests for cluster autoscaler

cc: @piosz @fgrzadkowski @jszczepkowski 

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Unify DeleteAllEtcdKeys in integration tests & start using namespaces in some tests

Getting rid of DeleteAllEtcdKeys() and running all tests in separate namespace is necessary to run integration tests in parallel.

Aside from that, this is first step of reducing amount of annoying logs in integration tests...

Automatic merge from submit-queue

WIP - Handle map[]struct{} in DeepCopy

Deep copy was not properly handling the empty struct case we use for Sets.

@lavalamp I need your expertise when you have some time - the go2idl parser is turning sets.String into the following tree:

    type:         sets.String           kind: Alias
      underlying: map[string]sets.Empty kind: Map
        key:      string                kind: Builtin
        elem:     set.Empty             kind: Struct
                                              ^
                                              should be Alias

Looking at tc.Named, I'm not sure what the expected outcome would be and why you flatten there.

Automatic merge from submit-queue

Make generated build tag parameterizable for go2idl

Downstream generators that want to reuse the upstream generated types
need to be able to define a different ignore tag (so that they can see
the already generated types).

@wojtek-t allows third parties to reuse conversions in api/v1 (for instance) because otherwise they are hidden when go2idl parses the dependency packages.

Automatic merge from submit-queue

Run builds as the calling user

This means no 'sudo' is needed to copy files out.

@wojtek-t @smarterclayton 

Is comparing the wrong field for bounds.