Move virtualcluster directory from WG repo

Author: Guo, Fei

virtualcluster/.gitignore

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+
+# Binaries for programs and plugins
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+_output
+coverage
+
+# Test binary, build with `go test -c`
+*.test
+
+# Output of the go coverage tool, specifically when used with LiteIDE
+*.out
+
+# Kubernetes Generated files - skip generated files, except for vendored files
+
+vendor/
+
+# editor and IDE paraphernalia
+.idea
+*.swp
+*.swo
+*~

virtualcluster/Dockerfile

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+# Build the manager binary
+FROM golang:1.12 as builder
+
+ENV GO111MODULE=on
+
+WORKDIR /go/virtualcluster
+
+COPY go.mod .
+COPY go.sum .
+
+RUN go mod download
+
+COPY pkg/    pkg/
+COPY cmd/    cmd/
+
+# Build
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build -a -o manager sigs.k8s.io/cluster-api-provider-nested/virtualcluster/cmd/manager
+
+# Copy the controller-manager into a thin image
+FROM ubuntu:latest
+WORKDIR /
+COPY --from=builder /go/virtualcluster/manager .
+ENTRYPOINT ["/manager"]

virtualcluster/Makefile

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+# Explicitly opt into go modules, even though we're inside a GOPATH directory
+export GO111MODULE=on
+
+# Image URL to use all building/pushing image targets
+DOCKER_REG ?= ${or ${VC_DOCKER_REGISTRY},"virtualcluster"}
+IMG ?= ${DOCKER_REG}/manager-amd64 ${DOCKER_REG}/vn-agent-amd64 ${DOCKER_REG}/syncer-amd64
+
+# TEST_FLAGS used as flags of go test.
+TEST_FLAGS ?= -v --race
+
+# COVERAGE_PACKAGES is the coverage we care about.
+COVERAGE_PACKAGES=$(shell go list ./... | \
+				  grep -v sigs.k8s.io/cluster-api-provider-nested/virtualcluster/pkg/client | \
+				  grep -v sigs.k8s.io/cluster-api-provider-nested/virtualcluster/pkg/apis | \
+				  grep -v sigs.k8s.io/cluster-api-provider-nested/virtualcluster/cmd | \
+				  grep -v sigs.k8s.io/cluster-api-provider-nested/virtualcluster/test/e2e)
+
+# CRD_OPTIONS ?= "crd:trivialVersions=true"
+CRD_OPTIONS ?= "crd:trivialVersions=true,maxDescLen=0"
+
+# Build code.
+#
+# Args:
+#   WHAT: Directory names to build.  If any of these directories has a 'main'
+#     package, the build will produce executable files under $(OUT_DIR).
+#     If not specified, "everything" will be built.
+#   GOFLAGS: Extra flags to pass to 'go' when building.
+#   GOLDFLAGS: Extra linking flags passed to 'go' when building.
+#   GOGCFLAGS: Additional go compile flags passed to 'go' when building.
+#
+# Example:
+#   make
+#   make all
+#   make all WHAT=cmd/kubelet GOFLAGS=-v
+#   make all GOLDFLAGS=""
+#     Note: Specify GOLDFLAGS as an empty string for building unstripped binaries, which allows
+#           you to use code debugging tools like delve. When GOLDFLAGS is unspecified, it defaults
+#           to "-s -w" which strips debug information. Other flags that can be used for GOLDFLAGS
+#           are documented at https://golang.org/cmd/link/
+.PHONY: all
+all: test build
+
+build: 
+	hack/make-rules/build.sh $(WHAT)
+
+# Run tests
+.PHONY: test
+PWD = $(CURDIR)
+test: generate fmt vet manifests
+	@mkdir -p coverage
+	@( for pkg in ${COVERAGE_PACKAGES}; do \
+		go test ${TEST_FLAGS} \
+			-coverprofile=coverage/unit-test-`echo $$pkg | tr "/" "_"`.out \
+			$$pkg || exit 1 ;\
+	done )
+	@( cd ./pkg/vn-agent/server/test; \
+		go test ${TEST_FLAGS} \
+			-coverprofile=${PWD}/coverage/unit-test-pkg_vn-agent_server_test.out )
+	@cd ${PWD}
+
+.PHONY: coverage
+coverage: ## combine coverage after test
+	@mkdir -p coverage
+	@gocovmerge coverage/* > coverage/coverage.txt
+	@go tool cover -html=coverage/coverage.txt -o coverage/coverage.html
+
+.PHONY: clean
+clean: ## clean to remove bin/* and files created by module
+	@go mod tidy
+	@rm -rf _output/*
+	@rm -rf coverage/*
+
+# Run against the configured Kubernetes cluster in ~/.kube/config
+run: generate fmt vet
+	go run ./cmd/manager/main.go
+
+# Install CRDs into a cluster
+install: manifests
+	kubectl apply -f config/crds
+
+# Deploy controller in the configured Kubernetes cluster in ~/.kube/config
+deploy: manifests
+	kubectl apply -f config/crds
+	kustomize build config/default | kubectl apply -f -
+
+# Generate manifests e.g. CRD, RBAC etc.
+manifests: controller-gen
+	$(CONTROLLER_GEN) $(CRD_OPTIONS) rbac:roleName=manager-role paths="./..." output:crd:artifacts:config=config/crds
+	hack/make-rules/replace-null.sh
+# To work around a known controller gen issue
+# https://github.com/kubernetes-sigs/kubebuilder/issues/1544
+ifeq (, $(shell which yq))
+	@echo "Please install yq for yaml patching. Get it from here: https://github.com/mikefarah/yq"
+	@exit
+else
+	@{ \
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.apiServer.properties.statefulset.properties.spec.properties.template.properties.spec.properties.containers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.controllerManager.properties.statefulset.properties.spec.properties.template.properties.spec.properties.containers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.etcd.properties.statefulset.properties.spec.properties.template.properties.spec.properties.containers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.apiServer.properties.statefulset.properties.spec.properties.template.properties.spec.properties.initContainers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.controllerManager.properties.statefulset.properties.spec.properties.template.properties.spec.properties.initContainers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.etcd.properties.statefulset.properties.spec.properties.template.properties.spec.properties.initContainers.items.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.apiServer.properties.service.properties.spec.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.controllerManager.properties.service.properties.spec.properties.ports.items.required[1]" protocol;\
+	yq w -i config/crds/tenancy.x-k8s.io_clusterversions.yaml "spec.validation.openAPIV3Schema.properties.spec.properties.etcd.properties.service.properties.spec.properties.ports.items.required[1]" protocol;\
+	}
+endif
+
+# Run go fmt against code
+fmt:
+	go fmt ./pkg/... ./cmd/...
+
+# Run go vet against code
+vet:
+	go vet ./pkg/... ./cmd/...
+
+# Generate code
+generate: controller-gen
+ifndef GOPATH
+	$(error GOPATH not defined, please define GOPATH. Run "go help gopath" to learn more about GOPATH)
+endif
+	$(CONTROLLER_GEN) object:headerFile="hack/boilerplate.go.txt" paths="./..."
+
+# Build release image.
+#
+# 1. run tests
+# 2. build docker image
+.PHONY: release-images
+release-images: test build-images
+
+# Build docker image.
+#
+# 1. build all binaries.
+# 2. copy binaries to the corresponding docker image.
+build-images:
+	hack/make-rules/release-images.sh $(WHAT)
+
+# Push the docker image
+docker-push:
+	$(foreach i,$(IMG),docker push $i;)
+
+# find or download controller-gen
+# download controller-gen if necessary
+controller-gen:
+ifeq (, $(shell which controller-gen))
+	@{ \
+	set -e ;\
+	CONTROLLER_GEN_TMP_DIR=$$(mktemp -d) ;\
+	cd $$CONTROLLER_GEN_TMP_DIR ;\
+	go mod init tmp ;\
+	go get sigs.k8s.io/controller-tools/cmd/[email protected] ;\
+	rm -rf $$CONTROLLER_GEN_TMP_DIR ;\
+	}
+CONTROLLER_GEN=$(GOPATH)/bin/controller-gen
+else
+CONTROLLER_GEN=$(shell which controller-gen)
+endif
+
+# Build and run kubernetes e2e tests.
+#
+# Args:
+#  KUBECONFIG: kubeconfig to virtual cluster. If empty, create a virtual cluster.
+#    Defaults to "".
+#  FOCUS: Regexp that matches the tests to be run.  Defaults to "\[Conformance\]".
+#  SKIP: Regexp that matches the tests that needs to be skipped.
+#    Defaults to "\[Flaky\]|\[Slow\]|\[Serial\]"
+#  BUILD_DEPENDENCIES: if true, build dependencies related to e2e test.
+#    Defaults to true.
+#
+# Example:
+#   make test-e2e-k8s KUBECONFIG=/path/to/vc-kubeconfig
+.PHONY: test-e2e-k8s
+test-e2e-k8s:
+	hack/make-rules/test-e2e-k8s.sh

virtualcluster/OWNERS

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+# See the OWNERS docs: https://git.k8s.io/community/contributors/guide/owners.md
+
+approvers:
+- adohe
+- Fei-Guo
+- resouer
+- tashimi
+- zhuangqh
+
+reviewers:
+- adohe
+- christopherhein
+- Fei-Guo
+- resouer
+- zhuangqh

virtualcluster/PROJECT

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+version: "1"
+domain: x-k8s.io
+projectName: virtualcluster
+repo: sigs.k8s.io/cluster-api-provider-nested/virtualcluster

virtualcluster/README.md

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+# VirtualCluster - Enabling Kubernetes Hard Multi-tenancy
+
+VirtualCluster represents a new architecture to address various Kubernetes control plane isolation challenges.
+It extends existing namespace based Kubernetes multi-tenancy model by providing each tenant a cluster view.
+VirtualCluster completely leverages Kubernetes extendability and preserves full API compatibility.
+That being said, the core Kubernetes components are not modified in virtual cluster.
+
+With VirtualCluster, each tenant is assigned a dedicated tenant control plane, which is a upstream Kubernetes distribution.
+Tenants can create cluster scope resources such as namespaces and CRDs in the tenant control plane without affecting others.
+As a result, most of the isolation problems due to sharing one apiserver disappear.
+The Kubernetes cluster that manages the actual physical nodes is called a super cluster, which now
+becomes a Pod resource provider. VirtualCluster is composed of the following components:
+
+- **vc-manager**: A new CRD [VirtualCluster](pkg/apis/tenancy/v1alpha1/virtualcluster_types.go) is introduced
+to model the tenant control plane. `vc-manager` manages the lifecycle of each `VirtualCluster` custom resource.
+Based on the specification, it either creates CAPN control plane Pods in local K8s cluster,
+or imports an existing cluster if a valid `kubeconfig` is provided.
+
+- **syncer**: A centralized controller that populates API objects needed for Pod provisioning from every tenant control plane
+to the super cluster, and bidirectionally syncs the object statuses. It also periodically scans the synced objects to ensure
+the states between tenant control plane and super cluster are consistent.
+
+- **vn-agent**: A node daemon that proxies all tenant kubelet API requests to the kubelet process that running
+in the node. It ensures each tenant can only access its own Pods in the node.
+
+With all above, from the tenant’s perspective, each tenant control plane behaves like an intact Kubernetes with nearly full API capabilities.
+For more technical details, please check our [ICDCS 2021 paper.](./doc/vc-icdcs.pdf) 
+
+## Live Demos/Presentations
+
+Kubecon EU 2020 talk (~25 mins) | WG meeting demo (~50 mins)
+--- | ---
+[![](http://img.youtube.com/vi/5RgF_dYyvEY/0.jpg)](https://www.youtube.com/watch?v=5RgF_dYyvEY "vc-kubecon-eu-2020") | [![](http://img.youtube.com/vi/Kow00IEUbAA/0.jpg)](http://www.youtube.com/watch?v=Kow00IEUbAA "vc-demo-long")
+
+## Quick Start
+
+Please follow the [instructions](./doc/demo.md) to install VirtualCluster in your local K8s cluster.
+
+## Abstraction
+
+In VirtualCluster, tenant control plane owns the source of the truth for the specs of all the synced objects. 
+The exceptions are persistence volume, storage class and priority class resources whose source of the truth is the super cluster.
+The syncer updates the synced object's status in each tenant control plane, 
+acting like a regular resource controller. This abstraction model means the following assumptions:
+- The synced object spec _SHOULD_ not be altered by any arbitrary controller in the super cluster.
+- Tenant master owns the lifecycle management for the synced object. The synced objects _SHOULD NOT_ be
+  managed by any controllers (e.g., StatefulSet) in the super cluster.
+
+If any of the above assumptions is violated, VirtualCluster may not work as expected. Note that this 
+does not mean that a cluster administrator cannot install webhooks, for example, a sidecar webhook, 
+in the super cluster. Those webhooks will still work but the changes are going
+to be hidden to tenants. Alternatively, those webhooks can be installed in tenant control planes so that
+tenants will be aware of all changes.
+
+## Limitations
+
+Ideally, tenants should not be aware of the existence of the super cluster in most cases. 
+There are still some noticeable differences comparing a tenant control plane and a normal Kubernetes cluster.
+
+- In the tenant control plane, node objects only show up after tenant Pods are created. The super cluster
+  node topology is not fully exposed in the tenant control plane. This means the VirtualCluster does not support
+  `DaemonSet` alike workloads in tenant control plane. Currently, the syncer controller rejects a newly
+  created tenant Pod if its `nodename` has been set in the spec. 
+
+- The syncer controller manages the lifecycle of the node objects in tenant control plane but
+  it does not update the node lease objects in order to reduce network traffic. As a result,
+  it is recommended to increase the tenant control plane node controller `--node-monitor-grace-period` 
+  parameter to a larger value ( >60 seconds, done in the sample clusterversion
+  [yaml](config/sampleswithspec/clusterversion_v1_nodeport.yaml) already).
+
+- Coredns is not tenant-aware. Hence, tenant should install coredns in the tenant control plane if DNS is required.
+The DNS service should be created in the `kube-system` namespace using the name `kube-dns`. The syncer controller can then
+recognize the DNS service's cluster IP in super cluster and inject it into any Pod `spec.dnsConfig`.
+
+- The cluster IP field in the tenant service spec is a bogus value. If any tenant controller requires the
+actual cluster IP that takes effect in the super cluster nodes, a special handling is required. 
+The syncer will backpopulate the cluster IP used in the super cluster in the 
+annotations of the tenant service object using `transparency.tenancy.x-k8s.io/clusterIP` as the key.
+Then, the workaround usually is going to be a simple code change in the controller. 
+This [document](./doc/tenant-dns.md) shows an example for coredns.
+
+- VirtualCluster does not support tenant PersistentVolumes. All PVs and Storageclasses are provided by the super cluster.
+
+VirtualCluster passes most of the Kubernetes conformance tests. One failing test asks for supporting
+`subdomain` which cannot be easily done in the VirtualCluster.
+
+## FAQ
+
+### Q: What is the difference between VirtualCluster and multi-cluster solution?
+
+One of the primary design goals of VirtualCluster is to improve the overall resource utilization
+of a super cluster by allowing multiple tenants to share the node resources in a control plane isolated manner. 
+A multi-cluster solution can achieve the same isolation goal but resources won't be shared causing
+nodes to have lower utilization.
+
+### Q: Can the tenant control plane run its own scheduler?
+
+VirtualCluster was primarily designed for serverless use cases where users normally do not have
+scheduling preferences. Using the super cluster scheduler can much easily
+achieve good overall resource utilization. For these reasons, 
+VirtualCluster does not support tenant scheduler. It is technically possible
+to support tenant scheduler by exposing some of the super cluster nodes directly in
+tenant control plane. Those nodes have to be dedicated to the tenant to avoid any scheduling
+conflicts. This type of tenant should be exceptional.
+
+### Q: What is the difference between Syncer and Virtual Kubelet? 
+
+They have similarities. In some sense, the syncer controller can be viewed as the replacement of a virtual
+kubelet in cases where the resource provider of the virtual kubelet is a Kubernetes cluster. The syncer 
+maintains the one to one mapping between a virtual node in tenant control plane and a real node
+in the super cluster. It preserves the Kubernetes API compatibility as closely as possible. Additionally, 
+it provides fair queuing to mitigate tenant contention.
+
+## Release
+
+The first release is coming soon.
+
+## Community
+VirtualCluster is a SIG cluster-api-provider-nested (CAPN) supporting project.
+If you have any questions or want to contribute, you are welcome to file issues or pull requests.
+
+You can also directly contact VirtualCluster maintainers via the WG [slack channel](https://kubernetes.slack.com/messages/wg-multitenancy).
+
+Lead developer: @Fei-Guo([email protected])