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>.
Fail container start if its requested device plugin resource is unknown.
With the change, Kubelet device manager now checks whether it has cached option state for the requested device plugin resource to make sure the resource is in ready state when we start the container.
**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 https://github.com/kubernetes/kubernetes/issues/67107
**Special notes for your reviewer**:
**Release note**:
```release-note
Fail container start if its requested device plugin resource hasn't registered after Kubelet restart.
```
Automatic merge from submit-queue (batch tested with PRs 66862, 67618). 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 bazel
**What this PR does / why we need it**:
`bazel test //cmd/kubeadm/...` has been broken for a while. This is incredibly annoying to me, because I use it constantly during my workflow. This should fix it.
**Special notes for your reviewer**:
**Release note**:
```release-note
```
Automatic merge from submit-queue (batch tested with PRs 66862, 67618). 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>.
Use sync.map to scale equiv class cache better
**What this PR does / why we need it**:
Change the current lock in first level ecache into `sync.Map`, which is known for scaling better than `sync. Mutex ` on machines with >8 CPUs
ref: https://golang.org/pkg/sync/#Map
And the code is much cleaner in this way.
5k Nodes, 10k Pods benchmark with ecache enabled in 64 cores VM:
```bash
// before
BenchmarkScheduling/5000Nodes/0Pods-64 10000 17550089 ns/op
// after
BenchmarkScheduling/5000Nodes/0Pods-64 10000 16975098 ns/op
```
Comparing to current implementation, the improvement after this change is noticeable, and the test is stable in 8, 16, 64 cores VM.
**Special notes for your reviewer**:
**Release note**:
```release-note
Use sync.map to scale ecache better
```
Automatic merge from submit-queue (batch tested with PRs 67493, 67617, 67582, 67337). 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 bug:DaemonSet didn't create pod after node have enough resource
**What this PR does / why we need it**:
Fix bug:DaemonSet didn't create pod after node have enough resource
**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#67225
**Special notes for your reviewer**:
NONE
**Release note**:
```release-note
DaemonSet: Fix bug- daemonset didn't create pod after node have enough resource
```
Automatic merge from submit-queue (batch tested with PRs 67493, 67617, 67582, 67337). 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>.
updates kibana to 6.3.2
**What this PR does / why we need it**:
* updates kibana to 6.3.2
**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**:
needed as es was updated to 6.3.2 too in https://github.com/kubernetes/kubernetes/pull/67484
**Release note**:
```release-note
updates kibana to 6.3.2
```
Automatic merge from submit-queue (batch tested with PRs 67493, 67617, 67582, 67337). 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>.
Tolerate nil input in GetValueFromIntOrPercent
**What this PR does / why we need it**:
`GetValueFromIntOrPercent` accepts pointer argument but does not validate it. This PR fixes that problem preventing from panics.
/assign @deads2k @sttts
**Release note**:
```release-note
NONE
```
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>.
Change rbd base image back to fedora 26
Due to the compatiblility issue for ceph server, it needs to change
back to fedora 26 from fedora 28, as a workaround.
**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#67269
**Special notes for your reviewer**:
/sig storage
@dims @rootfs
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 67596, 67520, 67605). 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>.
Cert list 2
**What this PR does / why we need it**:
Continuation of #67208. Uses the newly created declarative list of certificates kubeadm requires for the certs phase and upgrade steps.
**Special notes for your reviewer**:
**Release note**:
```release-note
```
Automatic merge from submit-queue (batch tested with PRs 67596, 67520, 67605). 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>.
Wait for Available in PV protection test
**What this PR does / why we need it**:
Just after creating a PV, its phase is "Pending" and its finalizers
doesn't contain "kubernetes.io/pv-protection". If the e2e test performs
so faster than the target k8s cluster, the test fails because the PV is
not ready. This adds WaitForPersistentVolumePhase() for waiting the
phase "Available" to avoid such situation.
**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#67519
**Release note**: NONE
Automatic merge from submit-queue (batch tested with PRs 67593, 67544). 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>.
fixes json logging in fluentd-elasticsearch image
**What this PR does / why we need it**:
* fixes json logging in fluentd-elasticsearch image by downgrading fluent-plugin-kubernetes_metadata_filter plugin to version 2.0.0
* adds missing pos files to fluentd config
* adds mapping type name
**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 #
* https://github.com/helm/charts/issues/7168
**Special notes for your reviewer**:
* https://github.com/fabric8io/fluent-plugin-kubernetes_metadata_filter/issues/145
* https://github.com/uken/fluent-plugin-elasticsearch/issues/442
**Release note**:
```release-note
fixes json logging in fluentd-elasticsearch image by downgrading fluent-plugin-kubernetes_metadata_filter plugin to version 2.0.0
```
Automatic merge from submit-queue (batch tested with PRs 67593, 67544). 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>.
Typo fix in returned message: ClusteRole->ClusterRole
There is a typo in returned message:
Line 143: ClusteRole->ClusterRole
Automatic merge from submit-queue (batch tested with PRs 55600, 67386). 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>.
update Annotations description about audit.Event
ref: https://github.com/kubernetes/kubernetes/pull/58679#discussion_r209375632
**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**:
/assign @liggitt
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 55600, 67386). 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>.
remove deplicate code for PodRequestsAndLimits
remove deplicate code for PodRequestsAndLimits
add unit test for PodRequestsAndLimits
**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
```
Automatic merge from submit-queue (batch tested with PRs 66592, 66639). 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>.
refactor some hard code in pkg/util/ipset/ipset.go
**What this PR does / why we need it**:
refactor some hard code in pkg/util/ipset/ipset.go
**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
```
Automatic merge from submit-queue (batch tested with PRs 66592, 66639). 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>.
add unit test for func EntryString in util/ipset
**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**:
add unit test for func EntryString in util/ipset
**Release note**:
```release-note
NONE
```
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>.
add --dns-loop-detect option to dnsmasq run by kube-dns
**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#67299
**Special notes for your reviewer**:
/cc @kubernetes/sig-network-pr-reviews
**Release note**:
```release-note
add --dns-loop-detect option to dnsmasq run by kube-dns
```
Automatic merge from submit-queue (batch tested with PRs 60790, 66023, 67549). 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>.
Removed istio related addon manifests, as the directory is deprecated.
**What this PR does / why we need it**:
the cluster/addon directory is deprecated, hence removing istio related addon manifests underneath.
**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
```
Automatic merge from submit-queue (batch tested with PRs 60790, 66023, 67549). 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>.
change TRUNCATED to DATA+OMITTED in kubectl config view
**What this PR does / why we need it**:
Based on the discussion in #61573, this PR switches the replacement text for CA certificate data and client certificates and secrets printed using `kubectl config view`. Currently, `REDACTED` is used, which might give a false impression that the data is a secret (which is not true for the public certificates).
This PR changes `REDACTED` to `DATA+OMITTED`. The printed string is the base64 encoded string on the byte stream. Some trickery is involved to print a readable string (refer to [this comment](https://github.com/kubernetes/kubernetes/pull/66023/files#diff-aec000ca3f293c94dcd99b4a9d1c5c3cL86) for more info).
**Which issue(s) this PR fixes**:
Fixes#61573
**Special notes for your reviewer**:
**Release note**:
```release-note
Switched certificate data replacement from "REDACTED" to "DATA+OMITTED"
```
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>.
add unit test for function AsScaledInt64
**What this PR does / why we need it**:
add unit test for function AsScaledInt64
**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
```
Automatic merge from submit-queue (batch tested with PRs 67041, 66948). 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>.
Anti affinity optimization
**What this PR does / why we need it**:
This pull request aims to optimize the performance of anti-affinity rules lookup of existing pods
This optimization maps the topology values to a list of pods running on nodes that match this value and store that map in the pod metadata. Accordingly, when validating anti-affinity rules of existing pods we will only check those running on nodes with similar topology values to the current candidate (node) for scheduling.
**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#63937
**Special notes for your reviewer**:
/sig scalability
/sig scheduling
**Release note**:
```release-note
improve performance of anti-affinity predicate of default scheduler.
```
Automatic merge from submit-queue (batch tested with PRs 67041, 66948). 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>.
50342: Establish '406 Not Acceptable' response for protobuf serializa…
…tion 'errNotMarshalable'
- Added metav1.Status() that enforces '406 Not Acceptable' response if
protobuf serialization is not fully supported for the API resource type.
- JSON and YAML serialization are supposed to be more completely baked
in, so serialization involving those, and general errors with seralizing
protobuf, will return '500 Internal Server Error'.
- If serialization failure occurs and original HTTP status code is
error, use the original status code, else use the serialization failure
status code.
- Write encoded API responses to intermediate buffer
- Use apimachinery/runtime::Encode() instead of
apimachinery/runtime/protocol::Encode() in
apiserver/endpoints/handlers/responsewriters/writers::SerializeObject()
- This allows for intended encoder error handling to fully work, facilitated by
apiserver/endpoints/handlers/responsewriters/status::ErrorToAPIResponse() before officially
writing to the http.ResponseWriter
- The specific part that wasn't working by ErrorToAPIResponse() was the
HTTP status code set. A direct call to
http.ResponseWriter::WriteHeader(statusCode) was made in
SerializeObject() with the original response status code, before
performing the encode. Once this
method is called, it can not again update the status code at a later
time, with say, an erro status code due to encode failure.
- Updated relevant apiserver unit test to reflect the new behavior
(TestWriteJSONDecodeError())
- Add build deps from make update for protobuf serializer
**What this PR does / why we need it**:
This PR fixes a bug that was blocking extensible error handling in the case that serializing response data fails, and implements a '406 Not Acceptable' status code response if protobuf marshal definitions are not implemented for an API resource type. See commit message for further details.
**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#50342
**Special notes for your reviewer**:
**Release note**:
```release-note
Fixed a bug that was blocking extensible error handling when serializing API responses error out. Previously, serialization failures always resulted in the status code of the original response being returned. Now, the following behavior occurs:
- If the serialization type is application/vnd.kubernetes.protobuf, and protobuf marshaling is not implemented for the requested API resource type, a '406 Not Acceptable is returned'.
- If the serialization type is 'application/json':
- If serialization fails, and the original status code was an failure (e.g. 4xx or 5xx), the original status code will be returned.
- If serialization fails, and the original status code was not a failure (e.g. 2xx), the status code of the serialization failure will be returned. By default, this is '500 Internal Server Error', because JSON serialization is our default, and not supposed to be implemented on a type-by-type basis.
```
Automatic merge from submit-queue (batch tested with PRs 66733, 67472). 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>.
add ut for PortPart()
**What this PR does / why we need it**:
improve ut coverage
**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
```
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>.
Add a feature to the scheduler to score fewer than all nodes in every scheduling cycle
**What this PR does / why we need it**:
Today, the scheduler scores all the nodes in the cluster in every scheduling cycle (every time a posd is attempted). This feature implements a mechanism in the scheduler that allows scoring fewer than all nodes in the cluster. The scheduler stops searching for more nodes once the configured number of feasible nodes are found. This can help improve the scheduler's performance in large clusters (several hundred nodes and larger).
This PR also adds a new structure to the scheduler's cache, called NodeTree, that allows scheduler to iterate over various nodes in different zones in a cluster. This is needed to avoid scoring the same set of nodes in every scheduling cycle.
**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#66627
**Special notes for your reviewer**:
This is a large PR, but broken into a few logical commits. Reviewing would be easier if you review by commits.
**Release note**:
```release-note
Add a feature to the scheduler to score fewer than all nodes in every scheduling cycle. This can improve performance of the scheduler in large clusters.
```
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>.
allow failed discovery on initial quota controller start
Fixes#65005
Aggregated API servers now correctly provide 503s on discovery endpoints for groups that cannot be reached. This means that the kube-controller-manager process is now sensitive to discovery failures in the quota controller. This change allows discovery failures in the initial quota replenishment controller resource discovery.
@liggitt suspects similar races exist to those he found GC last release, but this pull doesn't make that better or worse.
@kubernetes/sig-api-machinery-bugs
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>.
update github.com/imdario/mergo to v0.3.5
**What this PR does / why we need it**:
Updates github.com/imdario/mergo library to v0.3.5. We were pinned because of a functionality change in the dependency, however, a new function was introduced with similar functionality to the old.
There is apparently some Debian packaging issues (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=878254) because of this. I'm still not clear what those are, unless they are forcing the library to update, as opposed to using our `vendor/`.
That said, this will allow for some of those vendor conflicts to resolve for anyone else who is using client-go, so that's at least worthwhile.
**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#27543, fixes https://github.com/kubernetes/client-go/issues/431
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 67194, 67540). 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 framework.WaitForDaemonSets
* when daemonsets are not ready, wait for really them
* swap parameters in Logf so that they are more readable.
**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
```
Automatic merge from submit-queue (batch tested with PRs 67194, 67540). 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>.
Externalize PV/PVC informer for StorageObjectInUseProtection & NodeAuthorizer
**What this PR does / why we need it**:
/sig api-machinery
ref: #66680
We move on and make the change happen for PV/PVC.
> PV: NodeAuthorizer, StorageObjectInUseProtection
> PVC: StorageObjectInUseProtection
1. Externalize PV and PVC informers for `StorageObjectInUseProtection`
2. Copy utility functions for PV from `pkg/api/persistentvolume` to `pkg/api/v1/persistentvolume` and make it accept external types.
3. Bump PV informer in NodeAuthorizer
**Release note**:
```release-note
NONE
```
- Added metav1.Status() that enforces '406 Not Acceptable' response if
protobuf serialization is not fully supported for the API resource type.
- JSON and YAML serialization are supposed to be more completely baked
in, so serialization involving those, and general errors with seralizing
protobuf, will return '500 Internal Server Error'.
- If serialization failure occurs and original HTTP status code is
error, use the original status code, else use the serialization failure
status code.
- Write encoded API responses to intermediate buffer
- Use apimachinery/runtime::Encode() instead of
apimachinery/runtime/protocol::Encode() in
apiserver/endpoints/handlers/responsewriters/writers::SerializeObject()
- This allows for intended encoder error handling to fully work, facilitated by
apiserver/endpoints/handlers/responsewriters/status::ErrorToAPIResponse() before officially
writing to the http.ResponseWriter
- The specific part that wasn't working by ErrorToAPIResponse() was the
HTTP status code set. A direct call to
http.ResponseWriter::WriteHeader(statusCode) was made in
SerializeObject() with the original response status code, before
performing the encode. Once this
method is called, it can not again update the status code at a later
time, with say, an erro status code due to encode failure.
- Updated relevant apiserver unit test to reflect the new behavior
(TestWriteJSONDecodeError())
- Add build deps from make update for protobuf serializer
50342: Code review suggestion impl
- Ensure that http.ResponseWriter::Header().Set() is called before http.ResponseWriter::WriteHeader()
- This will avert a potential issue where changing the response media type to text/plain wouldn't work.
- We want to respond with plain text if serialization fails of the original response, and serialization also fails for the resultant error response.
50342: wrapper for http.ResponseWriter
- Prevent potential performance regression caused by modifying encode to use a buffer instead of streaming
- This is achieved by creating a wrapper type for http.ResponseWriter that will use WriteHeader(statusCode) on the first
call to Write(). Thus, on encode success, Write() will write the original statusCode. On encode failure, we pass control
onto responsewriters::errSerializationFatal(), which will process the error to obtain potentially a new status code, depending
on whether or not the original status code was itself an error.
50342: code review suggestions
- Remove historical note from unit test comment
- Don't export httpResponseWriterWithInit type (for now)
Automatic merge from submit-queue (batch tested with PRs 67062, 67169, 67539, 67504, 66876). 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>.
Update the kubectl plugin mechanism
**Release note**:
```release-note
The plugin mechanism functionality to closely follow the git plugin design
```
Replace the existing plugin mechanism with the design proposed in https://github.com/kubernetes/community/pull/2437.
~~_The full implementation of the plugin mechanism itself is entirely contained within the first commit._~~
## Walkthrough
Under the new design, there is no plugin installation or loading required to use plugins.
A plugin is simply any executable file on a user's PATH whose name begins with `kubectl-`.
- Plugins receive the inherited environment from the `kubectl` binary. All environment variables
accessible by `kubectl` become accessible by the plugin.
- Plugins decide which command path they wish to implement based on their name. For example, a plugin wanting to provide a new command `foo`, would simply be named `kubectl-foo`.
### Creating a plugin
Below is an example plugin, that we will use for this walkthrough. Plugins may be written in any language, and handle arguments and flags in any way, optionally (as a convention) providing a way to retrieve their version via a `version` subcommand.
```bash
#!/bin/bash
# optional argument handling
if [[ "$1" == "version" ]]
then
echo "1.0.0"
exit 0
fi
# optional argument handling
if [[ "$1" == "config" ]]
then
echo $KUBECONFIG
exit 0
fi
echo "I am a plugin named kubectl-foo"
```
### Using a plugin
To use a plugin, simply make it executable:
```bash
sudo chmod +x ./kubectl-foo
```
and place it anywhere in your PATH:
```bash
sudo mv ./kubectl-foo /usr/local/bin
```
You may now invoke your plugin as a `kubectl` command:
```bash
$ kubectl foo
I am a plugin named kubectl-foo
```
All args and flags are passed as-is to the executable:
```bash
$ kubectl foo version
1.0.0
```
All environment variables are also passed as-is to the executable:
```bash
$ export KUBECONFIG=~/.kube/config
$ kubectl foo config
/home/<user>/.kube/config
$ KUBECONFIG=/etc/kube/config kubectl foo config
/etc/kube/config
```
Additionally, the first argument that is passed to a plugin will always be the full path to the location where it was invoked (`$0` would equal `/usr/local/bin/kubectl-foo` in our example above).
### Plugin discoverability
Seeing as how the `kubectl plugin` command is left as a no-op with this PR (perhaps it could serve as an entrypoint towards additional plugin functionality in the future), a small subcommand has been included that _lists all available plugin executables on a user's PATH_, along with any warnings it finds.
Example usage of this new subcommand is included below:
```bash
$ kubectl plugin list
The following kubectl-compatible plugins are available:
test/fixtures/pkg/kubectl/plugins/kubectl-foo
plugins/kubectl-foo
- warning: plugins/kubectl-foo is overshadowed by a similarly named plugin: test/fixtures/pkg/kubectl/plugins/kubectl-foo
plugins/kubectl-invalid
- warning: plugins/kubectl-invalid identified as a kubectl plugin, but it is not executable
plugins/kubectl-bar
error: 2 plugin warnings were found
```
cc @kubernetes/kubectl-maintainers @kubernetes/sig-cli-pr-reviews @soltysh @seans3 @mengqiy
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