251 lines
10 KiB
Markdown
251 lines
10 KiB
Markdown
# Virtual Kubelet
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Virtual Kubelet is an open source [Kubernetes kubelet](https://kubernetes.io/docs/reference/generated/kubelet/)
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implementation that masquerades as a kubelet for the purposes of connecting Kubernetes to other APIs.
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This allows the nodes to be backed by other services like ACI, AWS Fargate, Hyper.sh, [IoT Edge](https://github.com/Azure/iot-edge-virtual-kubelet-provider) etc. The primary scenario for VK is enabling the extension of the Kubernetes API into serverless container platforms like ACI, Fargate, and Hyper.sh, though we are open to others. However, it should be noted that VK is explicitly not intended to be an alternative to Kubernetes federation.
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Virtual Kubelet features a pluggable architecture and direct use of Kubernetes primitives, making it much easier to build on.
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We invite the Kubernetes ecosystem to join us in empowering developers to build
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upon our base. Join our slack channel named, virtual-kubelet, within the [Kubernetes slack group](https://kubernetes.slack.com/).
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Please note this software is experimental and should not be used for anything
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resembling a production workload.
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The best description is "Kubernetes API on top, programmable back."
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#### Table of Contents
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* [How It Works](#how-it-works)
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* [Usage](#usage)
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* [Providers](#providers)
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+ [Alibaba Cloud ECI Provider](#alibaba-cloud-eci-provider)
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+ [Azure Container Instances Provider](#azure-container-instances-provider)
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+ [Azure Batch GPU Provider](./providers/azurebatch/README.md)
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+ [AWS Fargate Provider](#aws-fargate-provider)
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+ [Hyper.sh Provider](#hypersh-provider)
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+ [Service Fabric Mesh Provider](#service-fabric-mesh-provider)
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+ [Adding a New Provider via the Provider Interface](#adding-a-new-provider-via-the-provider-interface)
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* [Testing](#testing)
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+ [Testing the Azure Provider Client](#testing-the-azure-provider-client)
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* [Known quirks and workarounds](#known-quirks-and-workarounds)
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* [Contributing](#contributing)
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## How It Works
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The diagram below illustrates how Virtual-Kubelet works.
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## Usage
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Deploy a Kubernetes cluster and make sure it's reachable.
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Run the binary with your chosen provider:
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```bash
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./bin/virtual-kubelet --provider <your provider>
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```
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Now that the virtual-kubelet is deployed run `kubectl get nodes` and you should see
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a `virtual-kubelet` node.
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## Current Features
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- create, delete and update pods
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- container logs
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- get pod, pods and pod status
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- capacity
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- node addresses, node capacity, node daemon endpoints
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- operating system
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## Command-Line Usage
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```bash
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virtual-kubelet implements the Kubelet interface with a pluggable
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backend implementation allowing users to create kubernetes nodes without running the kubelet.
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This allows users to schedule kubernetes workloads on nodes that aren't running Kubernetes.
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Usage:
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virtual-kubelet [flags]
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virtual-kubelet [command]
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Available Commands:
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help Help about any command
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version Show the version of the program
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Flags:
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-h, --help help for virtual-kubelet
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--kubeconfig string config file (default is $HOME/.kube/config)
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--namespace string kubernetes namespace (default is 'all')
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--nodename string kubernetes node name (default "virtual-kubelet")
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--os string Operating System (Linux/Windows) (default "Linux")
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--provider string cloud provider
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--provider-config string cloud provider configuration file
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--taint string apply taint to node, making scheduling explicit
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Use "virtual-kubelet [command] --help" for more information about a command.
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```
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## Providers
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This project features a pluggable provider interface developers can implement
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that defines the actions of a typical kubelet.
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This enables on-demand and nearly instantaneous container compute, orchestrated
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by Kubernetes, without having VM infrastructure to manage and while still
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leveraging the portable Kubernetes API.
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Each provider may have its own configuration file, and required environmental variables.
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Providers must provide the following functionality to be considered a supported integration with Virtual Kubelet.
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1. Provides the back-end plumbing necessary to support the lifecycle management of pods, containers and supporting resources in the context of Kubernetes.
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2. Conforms to the current API provided by Virtual Kubelet.
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3. Does not have access to the Kubernetes API Server and has a well-defined callback mechanism for getting data like secrets or configmaps.
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### Alibaba Cloud ECI Provider
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Alibaba Cloud ECI(Elastic Container Instance) is a service that allow you run containers without having to manage servers or clusters.
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You can find more details in the [Alibaba Cloud ECI provider documentation](./providers/alicloud/README.md).
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#### Configuration File
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The alibaba ECI provider will read configuration file specified by the `--provider-config` flag.
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The example configure file is `providers/alicloud/eci.toml`.
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### Azure Container Instances Provider
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The Azure Container Instances Provider allows you to utilize both
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typical pods on VMs and Azure Container instances simultaneously in the
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same Kubernetes cluster.
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You can find detailed instructions on how to set it up and how to test it in the [Azure Container Instances Provider documentation](./providers/azure/README.md).
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#### Configuration File
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The Azure connector can use a configuration file specified by the `--provider-config` flag.
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The config file is in TOML format, and an example lives in `providers/azure/example.toml`.
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#### More Details
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See the [ACI Readme](providers/azure/README.md)
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### AWS Fargate Provider
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[AWS Fargate](https://aws.amazon.com/fargate/) is a technology that allows you to run containers
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without having to manage servers or clusters.
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The AWS Fargate provider allows you to deploy pods to [AWS Fargate](https://aws.amazon.com/fargate/).
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Your pods on AWS Fargate have access to VPC networking with dedicated ENIs in your subnets, public
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IP addresses to connect to the internet, private IP addresses to connect to your Kubernetes cluster,
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security groups, IAM roles, CloudWatch Logs and many other AWS services. Pods on Fargate can
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co-exist with pods on regular worker nodes in the same Kubernetes cluster.
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Easy instructions and a sample configuration file is available in the [AWS Fargate provider documentation](providers/aws/README.md).
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### Hyper.sh Provider
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The Hyper.sh Provider allows Kubernetes clusters to deploy Hyper.sh containers
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and manage both typical pods on VMs and Hyper.sh containers in the same
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Kubernetes cluster.
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```bash
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./bin/virtual-kubelet --provider hyper
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```
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### Service Fabric Mesh Provider
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The Service Fabric Mesh Provider allows you to deploy pods to Azure [Service Fabric Mesh](https://docs.microsoft.com/en-us/azure/service-fabric-mesh/service-fabric-mesh-overview).
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Service Fabric Mesh is a fully managed service that lets developers deploy microservices without managing the underlying infrastructure.
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Pods deployed to Service Fabric Mesh will be assigned Public IPs from the Service Fabric Mesh network.
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```
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./bin/virtual-kubelet --provider sfmesh --taint azure.com/sfmesh
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```
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More detailed instructions can be found [here](providers/sfmesh/README.md).
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### Adding a New Provider via the Provider Interface
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The structure we chose allows you to have all the power of the Kubernetes API
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on top with a pluggable interface.
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Create a new directory for your provider under `providers` and implement the
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following interface. Then add your new provider under the others in the
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[`vkubelet/provider.go`](vkubelet/provider.go) file.
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```go
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// Provider contains the methods required to implement a virtual-kubelet provider.
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type Provider interface {
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// CreatePod takes a Kubernetes Pod and deploys it within the provider.
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CreatePod(pod *v1.Pod) error
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// UpdatePod takes a Kubernetes Pod and updates it within the provider.
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UpdatePod(pod *v1.Pod) error
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// DeletePod takes a Kubernetes Pod and deletes it from the provider.
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DeletePod(pod *v1.Pod) error
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// GetPod retrieves a pod by name from the provider (can be cached).
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GetPod(namespace, name string) (*v1.Pod, error)
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// GetPodStatus retrievesthe status of a pod by name from the provider.
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GetPodStatus(namespace, name string) (*v1.PodStatus, error)
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// GetPods retrieves a list of all pods running on the provider (can be cached).
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GetPods() ([]*v1.Pod, error)
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// Capacity returns a resource list with the capacity constraints of the provider.
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Capacity() v1.ResourceList
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// NodeConditions returns a list of conditions (Ready, OutOfDisk, etc), which is polled periodically to update the node status
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// within Kubernetes.
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NodeConditions() []v1.NodeCondition
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// OperatingSystem returns the operating system the provider is for.
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OperatingSystem() string
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}
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```
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## Testing
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Running the unit tests locally is as simple as `make test`.
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### Testing the Azure Provider Client
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The unit tests for the [`azure`](providers/azure/) provider require a `credentials.json`
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file exist in the root of this directory or that you have `AZURE_AUTH_LOCATION`
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set to a credentials file.
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You can generate this file by following the instructions listed in the
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[README](providers/azure/client/README.md) for that package.
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## Known quirks and workarounds
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### Missing Load Balancer IP addresses for services
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#### When Virtual Kubelet is installed on a cluster, you cannot create external-IPs for a Service
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Kubernetes 1.9 introduces a new flag, `ServiceNodeExclusion`, for the control plane's Controller Manager. Enabling this flag in the Controller Manager's manifest allows Kubernetes to exclude Virtual Kubelet nodes from being added to Load Balancer pools, allowing you to create public facing services with external IPs without issue.
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#### Workaround
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Cluster requirements: Kubernetes 1.9 or above
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Enable the ServiceNodeExclusion flag, by modifying the Controller Manager manifest and adding `--feature-gates=ServiceNodeExclusion=true` to the command line arguments.
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## Contributing
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Virtual Kubelet follows the [CNCF Code of Conduct](https://github.com/cncf/foundation/blob/master/code-of-conduct.md).
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Sign the [CNCF CLA](https://github.com/kubernetes/community/blob/master/CLA.md) to be able to make Pull Requests to this repo.
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Weekly Virtual Kubelet Architecture meetings are held at 3pm PST [here](https://zoom.us/j/5337610301). Our google drive with design specifications and meeting notes are [here](https://drive.google.com/drive/folders/19Ndu11WBCCBDowo9CrrGUHoIfd2L8Ueg?usp=sharing).
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