New – AWS Fargate for Amazon EKS now supports Amazon EFS

AWS Fargate is a serverless compute engine for containers available with both Amazon Elastic Kubernetes Service (EKS) and Amazon Elastic Container Service (ECS). With Fargate, developers are able to focus on building applications, eliminating the need to manage the infrastructure related undifferentiated heavy lifting.

Developers specify resources for each Kubernetes pod, and are charged only for provisioned compute resource. When using Fargate, each EKS pod runs in its own kernel runtime environment and CPU, memory, storage, and network resources are never shared with other pods, providing workload isolation and increased security.

Containers are ephemeral in nature. They are dynamically scaled in and out, and their saved state or data is cleared on exit. We’ve had many requirements from our customers about data persistence and shared storage of containerized applications since launching EKS support for Fargate in 2019, and announced Amazon Elastic File System(EFS) support for Fargate on ECS in April 2020. Now many customers are operating stateful workloads on it, and others have requested support for EFS with Fargate when used with EKS. Today we are happy to announce this EFS support.

EFS provides a simple, scalable, and fully managed shared file system for use with AWS cloud services, and can also help Kubernetes applications be highly available because all data written to EFS is written to multiple AWS Availability Zones. EFS is built for on-demand petabyte growth without application interruption, and it automatically grows and shrinks as files are added and removed, eliminating the need to provision and manage capacity to accommodate growth. EFS Access Points is also ideal for security sensitive workloads as it can encrypt data in the file system and data in transit.

Kubernetes supports “Container Storage Interface (CSI)” which is a standard for exposing block and file storage systems to containerized workloads. The EFS CSI driver makes it simple to configure elastic file storage for Kubernetes clusters, and before this update customers could to use EFS via Amazon EC2 worker nodes connected to a cluster. Now customers can also configure their pods running on Fargate to access an EFS file system using standard Kubernetes APIs. With this update, customers can run stateful workloads that require highly available file systems as well as workloads that require access to shared storage. Using the EFS CSI driver, all data in transit is encrypted by default.

We released a generally available version of the Amazon EFS CSI driver for EKS in July 2020. The Amazon EFS CSI driver makes it easy to configure elastic file storage for both EKS and self-managed Kubernetes clusters running on AWS using standard Kubernetes interfaces. If a Kubernetes pod is terminated and relaunched, the CSI driver reconnects the EFS file system, even if the pod is relaunched in a different AWS Availability Zone.​ When using standard EC2 worker nodes, the EFS CSI driver needs to be deployed as a set of pods and DaemonSets. With this new update, for Fargate this step is not required and you do not need to install the EFS CSI driver, as it is installed in the Fargate stack and support for EFS is provided out of the box. Customers can use EFS with Fargate for EKS without spending the time and resources to install and update the CSI driver.

How to configure the Fargate/EKS and EFS integration?

You need to use three Kubernetes settings to mount EFS to Farfgate on EKS. Those are StorageClass, PersistentVolume (PV), and PersistentVolumeClaim (PVC). Configuring StorageClass and PVs are steps that an administrator (or similar) would do to make EFS file systems available for application developers. PVCs are used to allocate PVs from the pool of existing PVs as needed to deploy applications.

The StorageClass object provides a way for a Kubernetes administrator to register a specific storage type (e.g. EFS or EBS) and configuration (e.g. throughput, backup policy). Once a StorageClass is defined the PV object is used to create actual storage volumes inside that class. StorageClass and PV are the Kubernetes mechanisms that allow actual storage subsystems to be abstracted and decoupled from the way they are consumed by Kubernetes users. For example, while a Kubernetes administrator needs to know how exactly to configure a specific storage configuration from a particular storage service, Kubernetes users do not because they only see their volumes within abstract classes of storage.

The last step is the binding: Kubernetes users requests access to said volumes via the PVC object and related API. These volumes can be created dynamically when the user requests them via the PVC or they need to be statically pre-created by an administrator for later consumption by a Kubernetes user. The current implementation of the EFS CSI driver requires the volumes to be statically pre-created for the PVC binding to work.

If you are new to Kubernetes persistent volumes and want to know more about how they work, please refer to this page in the Kubernetes documentation that has all the details.

Let’s see this in action. First, you need to create your own EFS file system in the same AWS Region. If you are not familiar with EFS this EFS getting start guide is a good resource you can start with.

Once you create an EFS file system, you get your file system ID. You can configure the mount settings using a Kubernetes StorageClass and PersistentVolume. Here is an example of the YAML files:

CSIDriver Object

apiVersion: storage.k8s.io/v1beta1
kind: CSIDriver
metadata:
  name: efs.csi.aws.com
spec:
  attachRequired: false

For now you need to add the EFS CSIDriver object shown above to your cluster so Kubernetes can discover the driver that Fargate automatically installs. In the future, this manifest will be added by default to EKS clusters.

Storage Class

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: efs-sc
provisioner: efs.csi.aws.com

PersistentVolume(PV)

apiVersion: v1
kind: PersistentVolume
metadata:
  name: efs-pv
spec:
  capacity:
    storage: 5Gi
  volumeMode: Filesystem
  accessModes:
    - ReadWriteMany
  persistentVolumeReclaimPolicy: Retain
  storageClassName: efs-sc
  csi:
    driver: efs.csi.aws.com
    volumeHandle: <EFS filesystem ID>

The volumeHandle is returned by the EFS service when you create a file system, and you need to use it to configure the CSI driver to create the PV. You can obtain EFS filesystem ID from the AWS management console or the below command by AWS CLI.

aws efs describe-file-systems --query "FileSystems[*].FileSystemId" --output text

Now that you have created a PV by applying the manifest above, you configure Kurbenetes pods to access the EFS file system by including a PersistentVolumeClaim in the pod manifest. These are two manifest examples that do that:

PersistentVolumeClaim(PVC)

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: efs-claim
spec:
  accessModes:
    - ReadWriteMany
  storageClassName: efs-sc
  resources:
    requests:
      storage: 5Gi

Pod manifest

apiVersion: v1
kind: Pod
metadata:
  name: app1
spec:
  containers:
  - name: app1 image: busybox command: ["/bin/sh"] args: ["-c", "while true; do echo $(date -u) >> /data/out1.txt; sleep 5; done"]
    volumeMounts:
    - name: persistent-storage
      mountPath: /data
  volumes:
  - name: persistent-storage
    persistentVolumeClaim:
      claimName: efs-claim

Available Today

Today, this feature update is available for newly created EKS clusters with Kubernetes version 1.17, and we are planning to roll out support for this feature with additional Kubernetes versions on EKS in the coming weeks. This update is available in all AWS regions where Fargate with EKS is available. You can check our latest documentation for more detail.

– Kame;