Kubernetes is rapidly evolving, with frequent feature releases, functionality updates, and bug fixes. Additionally, AWS periodically changes the way it configures Amazon Elastic Container Service for Kubernetes (Amazon EKS) to improve performance, support bug fixes, and enable new functionality. Previously, moving to a new Kubernetes version required you to re-create your cluster and migrate your applications. This is a time-consuming process that can result in application downtime.

Today, I’m excited to announce that EKS now performs managed, in-place cluster upgrades for both Kubernetes and EKS platform versions. This simplifies cluster operations and lets you quickly take advantage of the latest Kubernetes features, as well as the updates to EKS configuration and security patches, without any downtime. EKS also now supports Kubernetes version 1.11.5 for all new EKS clusters.

Updates for Kubernetes and EKS

There are two types of updates that you can apply to your EKS cluster, Kubernetes version updates and EKS platform version updates. Today, EKS supports upgrades between Kubernetes minor versions 1.10 and 1.11.

As new Kubernetes versions are released and validated for use with EKS, we will support three stable Kubernetes versions as part of the update process at any given time.

EKS platform versions

The EKS platform version contains Kubernetes patches and changes to the API server configuration. Platform versions are separate from but associated with Kubernetes minor versions.

When a new Kubernetes version is made available for EKS, its initial control plane configuration is released as the “eks.1” platform version. AWS releases new platform versions as needed to enable Kubernetes patches. AWS also releases new versions when there are EKS API server configuration changes that could affect cluster behavior.

Using this versioning scheme makes it possible to independently update the configuration of different Kubernetes versions. For example, AWS might need to release a patch for Kubernetes version 1.10 that is incompatible with Kubernetes version 1.11.

Currently, platform version updates are automatic. AWS plans to provide manual control over platform version updates through the UpdateClusterVersion API operation in the future.

Using the update API operations

There are three new EKS API operations to enable cluster updates:

• UpdateClusterVersion
• ListUpdates
• DescribeUpdates

The UpdateClusterVersion operation can be used through the EKS CLI to start a cluster update between Kubernetes minor versions:

aws eks update-cluster-version --name Your-EKS-Cluster --kubernetes-version 1.11

You only need to pass in a cluster name and the desired Kubernetes version. You do not need to pick a specific patch version for Kubernetes. We pick patch versions that are stable and well-tested. This CLI command returns an “update” API object with several important pieces of information:

{
    "update" : {
        "updateId" : UUID,
        "updateStatus" : PENDING,
        "updateType" : VERSION-UPDATE
        "createdAt" : Timestamp
     }
 }

This update object lets you track the status of your requested modification to your cluster. This can show you if there was there an error due to a misconfiguration on your cluster and if the update in progress, completed, or failed.

You can also list and describe the status of the update independently, using the following operations:

aws eks list-updates --name Your-EKS-Cluster

This returns the in-flight updates for your cluster:

{
    "updates" : {
        "UUID-1",
        "UUID-2"
     },
     "nextToken" : null
 }

Finally, you can also describe a particular update to see details about the update’s status:

aws eks describe-update --name Your-EKS-Cluster --update-id UUID

{
    "update" : {
        "updateId" : UUID,
        "updateStatus" : FAILED,
        "updateType" : VERSION-UPDATE
        "createdAt" : Timestamp
        "error": {
            "errorCode" : DependentResourceNotFound
            "errorMessage" : The Role used for creating the cluster is deleted.
            "resources" : ["aws:iam:arn:role"] 
     }
 }

Considerations when updating

New Kubernetes versions introduce significant changes. I highly recommend that you test the behavior of your application against a new Kubernetes version before performing the update on a production cluster.

Generally, I recommend integrating EKS into your existing CI workflow to test how your application behaves on a new version before updating your production clusters.

Worker node updates

Today, EKS does not update your Kubernetes worker nodes when you update the EKS control plane. You are responsible for updating EKS worker nodes. You can find an overview of this process in Worker Node Updates.

The EKS team releases a set of EKS-optimized AMIs for worker nodes that correspond with each version of Kubernetes supported by EKS. You can find these AMIs listed in the documentation, and you can find the build configuration in a version-specific branch of the Amazon-EKS-AMI GitHub repository .

Getting started

You can start using Kubernetes version 1.11 today for all new EKS clusters. Use cluster updates to move to version 1.11 for all existing EKS clusters. You can learn more about the update process and APIs in our documentation.