AWS Open Source Blog

Running AWS Fargate with virtual-kubelet

使用 virtual-kubelet 运行 AWS Fargate

AWS Fargate is a new technology that allows you to run containers without having to provision, manage, or scale servers.

Today, Fargate is natively integrated with Amazon Elastic Container Service (ECS). Since we announced Fargate at re:Invent 2017, many customers have told us that they were very interested in using Fargate to run Kubernetes. To help make this happen, we’ve started exploring using virtual-kubelet to connect Fargate and Kubernetes.

Virtual-kubelet is an open source, community-driven project that allows Kubernetes worker nodes to be backed by any compute resource. We have written a new provider plugin that allows virtual-kubelet to create Fargate tasks, and have merged this plugin into the virtual-kubelet upstream project.

This new plugin is an exploratory step towards extending AWS Fargate’s managed data plane to Kubernetes, and we have a lot to do before it works seamlessly for all use cases. For now, here are few simple steps to try it for yourself:

Step 1: Set up a single-master Kubernetes cluster using kops

We will set up a simple test environment to showcase Kubernetes workloads backed by AWS Fargate.

virtual-kubelet and Fargate

The first step is to set up a kops cluster. In our kops set-up we are using a hybrid environment with two EC2 worker nodes and one virtual-kubelet instance. Any Kubernetes workloads that are not supported on Virtual-Kubelet and Fargate, can easily be scheduled as usual on the two worker nodes. Follow the instructions below using this repository: github.com/kubernetes/kops/blob/master/docs/aws.md. Our blog post on managing Kubernetes clusters on AWS using kops may also be helpful.

$ export KUBERNETES_VERSION=https://storage.googleapis.com/kubernetes-release/release/v1.9.0/
$ export AWS_AVAILABILITY_ZONES=us-east-1
$ export CLUSTER_NAME=dnishi-kops1.k8s.local

$ kops create cluster —name $CLUSTER_NAME —zones $AWS_AVAILABILITY_ZONES —kubernetes-version $KUBERNETES_VERSION --yes

##Tested with Kubernetes v1.8.0+
##Kops 1.6.2+ can be easily created as a gossip-based cluster and the cluster name has to end with k8s.local

Once the kops install finishes, verify your nodes are running with kubectl:

$ kubectl get nodes
NAME                            STATUS    ROLES     AGE       VERSION
ip-172-20-42-7.ec2.internal     Ready     master    5h        v1.9.0
ip-172-20-44-230.ec2.internal   Ready     node      5h        v1.9.0
ip-172-20-58-31.ec2.internal    Ready     node      5h        v1.9.0

Copy the kubeconfig file for the kops cluster and save it. You will need this file on the EC2 instance where virtual-kubelet will run.

Step 2: Make a virtual-kubelet build from the upstream repository

Before you build, make sure you have installed Go. For a first time user set the variables as follows:

$ export GOPATH=$HOME/go

We’ll use github.com/virtual-kubelet as our base path.

$ mkdir -p $GOPATH/src/github.com/virtual-kubelet
$ cd $GOPATH/src/github.com/virtual-kubelet

If you are cloning this repo for the first time, use the commands below. If you have previously cloned virtual-kublet, replace `git clone` with `git pull` in the commands below.

$ git clone https://github.com/virtual-kubelet/virtual-kubelet
$ cd virtual-kubelet
$ make build

All dependencies are vendored-in to the repository and will be built together with virtual-kubelet. The binary is placed in virtual-kubelet/bin directory.

Step 3: Create your Fargate task

If you haven’t used AWS Fargate before, the easiest way to get started is with Fargate’s first run experience. This will set up Fargate in your AWS account with the default settings. It will create a default Fargate cluster*, IAM roles, and a default VPC with an internet gateway and a default security group. After the first run, it’s easy to fine-tune individual settings. Once you have your first application on Fargate running, visit the AWS ECS console to take a closer look at your Fargate resources. Take a note of the sample-app’s subnets and security groups.

*because Fargate abstracts away servers, the cluster is used only as a logical construct to group running containers.

Step 4: Create an EC2 instance to run virtual-kubelet with the Fargate provider plugin

Create an IAM Role for the EC2 instance. Many AWS services require that you use roles to control what a service can access. When an IAM role serves a specialized purpose for a service, it is categorized as a service role for EC2 instances (for example), or a service-linked role. The EC2 instance running virtual-kubelet needs full access to the ECS APIs. Use the following steps to create the right IAM role:

Using AWS Console:

  1. Select IAM Roles on the AWS console in the us-east-1 region.
  2. Create role, select AWS service, Choose EC2 as the service that will use this role and click “Next: Permissions.”
  3. Search for “AmazonECS_FullAccess”, select it and click “Next: Review.”
  4. Name the role as “VK-ECSFullAccess” and complete. You will see the new role appear on the IAM Roles page.

Using aws-cli:

Create the role and attach the trust policy that enables EC2 to assume this role:

$ aws iam create-role --role-name VK-ECSFullAccess --assume-role-policy-document file://VK-Role-Trust-Policy.json

Here is the VK-Role-Trust-Policy.json:

$ cat VK-Role-Trust-Policy.json
{
  "Version": "2012-10-17",
  "Statement": {
    "Effect": "Allow",
    "Principal": {"Service": "ec2.amazonaws.com"},
    "Action": "sts:AssumeRole"
  }
}

Call the attach-role-policy command to grant this IAM role permission to access resources in your account:

$ aws iam attach-role-policy --role-name VK-ECSFullAccess --policy-arn arn:aws:iam::aws:policy/AmazonECS_FullAccess

Create the instance profile required by EC2 to contain the role:

$ aws iam create-instance-profile --instance-profile-name EC2-AmazonECS_FullAccess

Finally, add the role to the instance profile:

$ aws iam add-role-to-instance-profile --instance-profile-name EC2-AmazonECS_FullAccess --role-name VK-ECSFullAccess

Create the EC2 instance and attach the new role to it:

  • Use the EC2 console to create an EC2 node in the same VPC and Subnet as the other kops worker nodes and add the VK-ECSFullAccess-Role to the EC2 node during creation.
  • Alternately, use these aws-cli commands:

Create an ec2 Debian GNU/Linux 8 (Jessie) instance within the same subnet and security group as the kops worker nodes:

$ aws ec2 run-instances --image-id ami-b14ba7a7 --count 1 --instance-type t2.micro --key-name ${MyKeyPair-xxxxx} --security-group-ids ${sg-xxxxxxxx} --subnet-id ${subnet-xxxxxxxx} --associate-public-ip-address

Call the associate-iam-instance-profile command to attach the instance profile, YourNewRole-Instance-Profile, for the newly created IAM role, YourNewRole, to your EC2 instance, YourInstanceId:

$ aws ec2 associate-iam-instance-profile --instance-id ${i-xxxxxxxxxxxxx} --iam-instance-profile Name=EC2-AmazonECS_FullAccess

Verify that the IAM role is now attached to the instance by calling the describe-iam-instance-profile-association command:

$ aws ec2 describe-iam-instance-profile-associations

Copy the following files to the new EC2 node:

  • “virtual-kubelet” binary
  • fargate.toml config file. Update the fargate.toml file with the subnet, security group values from STEP 3. Also, change AssignPublicIPv4Address = true, if you want to access images from outside.
  • “kubeconfig” file from the kops cluster. Move this file to the path /root/.kube/config
$ scp -r -i ${path-to-MyKeyPair-xxxxx} ${path-to-virtual-kubelet/providers/aws/fargate.toml} ~/.kube/config admin@ec2.xx-xxx-xxx-xx.compute-1.amazonaws.com
$ ssh -i ${path-to-MyKeyPair-xxxxx} admin@ec2.xx-xxx-xxx-xx.compute-1.amazonaws.com
$ sudo -i
$ mv config /root/.kube/config

Run virtual-kubelet and keep the process running:

$ ./virtual-kubelet --provider aws --provider-config fargate.toml

Step 5: Confirm from your kubectl client that the cluster is ready

Once virtual-kubelet process is initiated, you will see it register as an agent onto the cluster.

$ kubectl get nodes
NAME                            STATUS    ROLES     AGE       VERSION
ip-172-20-42-7.ec2.internal     Ready     master    1d        v1.9.0
ip-172-20-44-230.ec2.internal   Ready     node      1d        v1.9.0
ip-172-20-58-31.ec2.internal    Ready     node      1d        v1.9.0
virtual-kubelet                 Ready     agent     14s       v1.8.3

Step 6: Create Kubernetes objects (pods, deployments, replica sets, services)

Deploy nginx with three replicas by using a text editor to create a YAML file with these contents and running it. To assign pods on Fargate (virtual-kubelet), we use nodeSelector constraint in the manifest, which is a field of PodSpec. It specifies a map of key-value pairs. You can also use Kubernetes taints to simulate this behavior.

nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.7.9
        ports:
        - containerPort: 80
        imagePullPolicy: IfNotPresent
        resources:
          requests:
            memory: "256Mi"
            cpu: "250m"
          limits:
            memory: "1000Mi"
            cpu: "500m"
      nodeSelector:
        type: virtual-kubelet

Now, deploy the YAML file you created:

$ kubectl create -f nginx-deployment.yaml
deployment.apps "nginx-deployment" created
$ kubectl get deployments -o wide
NAME              DESIRED  CURRENT  UP-TO-DATE  AVAILABLE  AGE  CONTAINERS  IMAGES       SELECTOR
nginx-deployment     3       3         3             0     12s  nginx       nginx:1.7.9 app=nginx

$ kubectl get pods -o wide
NAME                               READY      STATUS      RESTARTS     AGE     IP          NODE
nginx-deployment-6b488d64b-47hvk   1/1        Running     0            2m      10.0.1.23   virtual-kubelet
nginx-deployment-6b488d64b-dj45s   1/1        Running     0            2m      10.0.1.161  virtual-kubelet
nginx-deployment-6b488d64b-p6vsb   1/1        Running     0            2m      10.0.1.95   virtual-kubelet

Notice the nginx pod metadata in bold is reflected in the Fargate Dashboard below as a task definition.

Let’s update the nginx-deployments running on Fargate from v1.7.9 to v1.9.1:

$ kubectl set image deployment/nginx-deployment nginx=nginx:1.9.1

deployment.apps "nginx-deployment" image updated

$ kubectl rollout status deployment/nginx-deployment
Waiting for rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for rollout to finish: 1 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 2 out of 3 new replicas have been updated...
Waiting for rollout to finish: 1 old replicas are pending termination...
Waiting for rollout to finish: 1 old replicas are pending termination...
deployment "nginx-deployment" successfully rolled out

Fargate tasks also get updated one task at a time. If you click on a task, you can see the image version update from v1.7.9 to v1.9.1. Within seconds, each task updates to v1.9.1 and this process repeats for each task one at a time.


Deploy 20 pods with a single command. Use the nginx-deployment-new.yaml. As reflected in the Fargate dashboard, the tasks are created in seconds:

$ kubectl create -f nginx-deployment-new.yaml
deployment.apps "nginx-deployment" created

$ kubectl get deployments -o wide
NAME              DESIRED  CURRENT  UP-TO-DATE  AVAILABLE  AGE  CONTAINERS  IMAGES      SELECTOR
nginx-deployment    20       20       20           0       14s    nginx  nginx:1.7.9   app=nginx

Closing Thoughts

Today, the virtual-kubelet provider plugin does not support every Kubernetes use case and application pattern. This is our first step to give Kubernetes users a new way to think about compute, and we are excited to engage with the community on how best to implement nodeless design concepts for Kubernetes. We hope you will join us on this journey, suggest ideas, contribute code, and help test this plugin for your applications.
Here’s how you can participate:

AWS will be at KubeCon EU in Copenhagen, Denmark on May 2nd to 4th 2018 , demonstrating this integration as well as our upcoming managed Kubernetes service, Amazon Elastic Container Service for Kubernetes (Amazon EKS).


NOTE: This post is written specifically for intermediate-level users. A grasp of Linux, Go, Docker, and K8s is expected. Also, virtual-kubelet is not yet a stable code base. Don’t be surprised if virtual-kubelet crashes. We need help to make it stable!

Nishi Davidson

Nishi Davidson

Nishi Davidson has been in the cloud infrastructure and software application space for 15 years working across engineering, product management and strategy in South East Asia and the US markets. Currently she is responsible for AWS’s open source engineering efforts in the Kubernetes community. In the past, she ran SAP’s private cloud, Kubernetes managed service engineering for internal BUs. Nishi has led product/field engineering teams and introduced multiple cloud products/solutions to the market while working at HP, TCS, Juniper Networks, NetApp and DSSD (EMC). Nishi holds an MBA from Massachusetts Institute of Technology, Sloan and a bachelor’s in Electrical and Electronics Engineering from CEG, Guindy, Anna University.

Onur Filiz

Onur Filiz

Onur Filiz started coding during the 8-bit home computer era and never stopped since then. He is currently a Principal Software Engineer in AWS, working on Elastic Container Service (ECS), Elastic Container Service for Kubernetes (EKS) and AWS Fargate. His past work areas include operating systems, networking, containers and the cloud. Onur holds an M.Sc. in Telecommunications and Computer Networks from GWU and a B.Sc. in Computer Science from Ege University. You can get in touch with him on Twitter @onurfz.