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Kip, the Kubernetes Cloud Instance Provider

Kip is a Virtual Kubelet provider that allows a Kubernetes cluster to transparently launch pods onto their own cloud instances. Kip's virtual-kubelet pod is run on a cluster and will create a virtual Kubernetes node in the cluster. When a pod is scheduled onto the Virtual Kubelet, Kip starts a right-sized cloud instance for the pod’s workload and dispatches the pod onto the instance. When the pod is finished running, the cloud instance is terminated. We call these cloud instances “cells”.

When workloads run on Kip, your cluster size naturally scales with the cluster workload, pods are strongly isolated from each other and the user is freed from managing worker nodes and strategically packing pods onto nodes. This results in lower cloud costs, improved security and simpler operational overhead.

Table of Contents

Installation

There are two ways to get Kip up and running in AWS.

  • Option 1: Use the provided terraform scripts to create a new VPC and a new kubernetes cluster with a single Kip node.
  • Option 2: Add Kip to an existing kubernetes cluster.

Installation Option 1: Create a Minimal K8s Cluster

Prequisites:

In deploy/terraform, you will find a terraform config that creates a simple one master, one worker cluster and starts a Kip deployment.

cd deploy/terraform
terraform init
cp env.tfvars.example myenv.tfvars
vi myenv.tfvars  # customize variables as necessary
terraform apply -var-file myenv.tfvars

Installation Option 2: Using an Existing Cluster

To deploy Kip into an existing cluster, you'll need to setup cloud credentials that allow the Kip provider to manipulate cloud instances, security groups and other cloud resources. Once credentials are setup, apply deploy/virtual-kubelet.yaml to create the necessary kubernetes resources to support and run the provider.

Step 1: Credentials

In AWS, Kip can either use API keys supplied in the Kip provider configuration file (provider.yaml) or use the instance profile of the machine the Kip virtual-kubelet pod is running on.

Credentials Option 1 - Configuring AWS API keys:

Open deploy/virtual-kubelet.yaml in an editor, find the virtual-kubelet-config ConfigMap and fill in the values for accessKeyID and secretAccessKey under data.provider.yaml.cloud.aws.

Credentials Option 2 - Instance Profile Credentials:

In AWS, Kip can use credentials supplied by the instance profile attached to the node the pod is dispatched to. To use an instance profile, create an IAM policy with the minimum Kip permissions then apply the instance profile to the node that will run the Kip provider pod. The Kip pod must run on the cloud instance that the instance profile is attached to.

Step 2: Apply virtual-kubelet.yaml

The resources in deploy/manifests/virtual-kubelet create ServiceAccounts, Roles and a virtual-kubelet Deployment to run the provider. Kip is not stateless, the manifest will also create a PersistentVolumeClaim to store the provider data.

kubectl apply -k deploy/manifests/virtual-kubelet/base

After applying, you should see a new virtual-kubelet pod in the kube-system namespace and a new node named virtual-kubelet in the cluster.

Running Pods on Virtual Kubelet

To assign pods to run on the virtual kubelet node, add the following node selector and toleration to the pod spec in manifests.

spec:
  nodeSelector:
    type: virtual-kubelet
  tolerations:
  - key: virtual-kubelet.io/provider
    operator: Exists

Uninstall

If you used the provided terraform config for creating your cluster, you can remove the VPC and the cluster via:

terraform destroy -var-file <env.tfvars>.

If you deployed Kip in an existing cluster, make sure that you first remove all the pods and deployments that have been created by Kip. Then remove the virtual-kubelet deployment via:

kubectl delete -n kube-system deployment virtual-kubelet

Current Status

Features

  • Networking, including host network mode, cluster IPs, DNS, HostPorts and NodePorts
  • Pods will be started on a cloud instance that matches the pod resource requests/limits. If no requests/limits are present in the pod spec, Kip will fall back to a default cloud instance type specified in provider-config.yaml
  • GPU instances
  • Logs
  • Exec
  • Stats
  • Readiness/Liveness probes
  • Service account token automounts in pods.
  • Security Groups
  • Attaching instance profiles to Cells via annotations
  • The following volume types are supported
    • EmptyDir
    • ConfigMap
    • Secret
    • HostPath
    • Projected ConfigMaps and Secrets

Limitations

  • Stateful workloads and PersistentVolumes are not supported.
  • No support for updating ConfigMaps and Secrets for running Pods and Cells.
  • Virtual-kubelet has limitations on what it supports in the Downward API, e.g. pod.status.podIP is not supported
  • VolumeMounts do not support readOnly, subPath and subPathExpr attributes.
  • VolumeMount mountPropagation is always Bidirectional
  • Unsupported pod attributes:
    • EphemeralContainers
    • ReadinessGates
    • Lifecycle handlers
    • TerminationGracePeriodSeconds
    • ActiveDeadlineSeconds
    • Subdomain
    • HostAliases
    • VolumeDevices
    • TerminationMessagePolicy FallbackToLogsOnError is not implemented
    • The following PodSecurityContext fields
      • FSGroup
      • RunAsNonRoot
      • ShareProcessNamespace
      • HostIPC
      • HostPID

We are actively working on adding missing features. One of the main objectives of the project is to provide full support for all Kubernetes features.

FAQ

Q. I’ve seen the name Milpa mentioned in the logs and source code. What is Milpa?

A. Kip’s source code was adapted from an earlier project developed at Elotl called Milpa. We will be migrating away from that name in coming releases. Milpa started out as a stand alone unikernel (and later container) orchestration system and it was natural to move a subset of its functionality into an open source virtual-kubelet provider.

Q. How long does it take to start a workload?

A. In AWS, instances boot in under a minute, usually pods are dispatched to the instance in about 45 seconds. Depending on the size of the container image, a pod will be running in 60 to 90 seconds. In our experience, starting pods in Azure can be a bit slower with startup times between 1.5 to 3 minutes.

Q. Does it work with the Horizontal Pod Autoscaler and Vertical Pod Autoscaler?

A. Yes it does. However, to use the VPA with the provider, the pod must be dispatched to a new cloud instance.

Q. Are DaemonSets supported?

A. Yes, though they might not work the way intended. The pod will start on a separate cloud instance, and not on the node. It's possible to patch a DaemonSet so it does not get dispatched to the virtual-kubelet.

Q. Are you a kubernetes conformant runtime?

A. We are not 100% conformant at this time but we are working towards getting as close as possible to conformance. Currently Kip passes 70-80% of conformance tests but are hoping to get those values above 90% soon.

Q. What cloud providers does Kip support

A. Kip is currently GA on AWS and pre-alpha on Azure.

Q. What components make up the Kip system?

A. The following repositories are part of the Kip system

  • Itzo containes the cell agent and code for building cell images
  • Tosi for downloading images to cells
  • Cloud-Init a minimal cloud-init implementation

Q. We have our custom built AMI. Can I use it for running cells?

A. Yes, take a look at Bring your Own AMI.

How it Works

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