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Abhishek Gupta for AWS

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Use AWS Controllers for Kubernetes to deploy a solution consisting of Lambda, DynamoDB and API Gateway

#kubernetes #serverless #tutorial #go

In this blog post, you will be using AWS Controllers for Kubernetes on an Amazon EKS cluster to put together a solution where HTTP requests sent to a REST endpoint exposed by Amazon API Gateway are processed by a Lambda function and persisted to a DynamoDB table.

Image description

AWS Controllers for Kubernetes (also known as ACK leverage Kubernetes Custom Resource and Custom Resource Definitions and give you the ability to manage and use AWS services directly from Kubernetes without needing to define resources outside of the cluster. The idea behind ACK is to enable Kubernetes users to describe the desired state of AWS resources using the Kubernetes API and configuration language. ACK will then take care of provisioning and managing the AWS resources to match the desired state. This is achieved by using Service controllers that are responsible for managing the lifecycle of a particular AWS service. Each ACK service controller is packaged into a separate container image that is published in a public repository corresponding to an individual ACK service controller.

There is no single ACK container image. Instead, there are container images for each individual ACK service controller that manages resources for a particular AWS API.

This blog post will walk you through how to use the API Gateway, DynamoDB and Lambda service controllers for ACK.

Prerequisites

To follow along step-by-step, in addition to an AWS account, you will need to have AWS CLI, kubectl and helm installed.

There are a variety of ways in which you can create an Amazon EKS cluster. I prefer using eksctl CLI because of the convenience it offers. Creating an an EKS cluster using eksctl, can be as easy as this:

eksctl create cluster --name <my-cluster> --region <region-code>
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For details, refer to the Getting started with Amazon EKS – eksctl.

Clone this GitHub repository and change to the right directory:

git clone https://github.com/abhirockzz/k8s-ack-apigw-lambda

cd k8s-ack-apigw-lambda
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Ok let's get started!

Setup the ACK service controllers for AWS Lambda, API Gateway and DynamoDB

Install ACK controllers

Log into the Helm registry that stores the ACK charts:

aws ecr-public get-login-password --region us-east-1 | helm registry login --username AWS --password-stdin public.ecr.aws
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Deploy the ACK service controller for Amazon Lambda using the lambda-chart Helm chart:

RELEASE_VERSION_LAMBDA_ACK=$(curl -sL "https://api.github.com/repos/aws-controllers-k8s/lambda-controller/releases/latest" | grep '"tag_name":' | cut -d'"' -f4)

helm install --create-namespace -n ack-system oci://public.ecr.aws/aws-controllers-k8s/lambda-chart "--version=${RELEASE_VERSION_LAMBDA_ACK}" --generate-name --set=aws.region=us-east-1
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Deploy the ACK service controller for API Gateway using the apigatewayv2-chart Helm chart:

RELEASE_VERSION_APIGWV2_ACK=$(curl -sL "https://api.github.com/repos/aws-controllers-k8s/apigatewayv2-controller/releases/latest" | grep '"tag_name":' | cut -d'"' -f4)

helm install --create-namespace -n ack-system oci://public.ecr.aws/aws-controllers-k8s/apigatewayv2-chart "--version=${RELEASE_VERSION_APIGWV2_ACK}" --generate-name --set=aws.region=us-east-1
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Deploy the ACK service controller for DynamoDB using the dynamodb-chart Helm chart:

RELEASE_VERSION_DYNAMODB_ACK=$(curl -sL "https://api.github.com/repos/aws-controllers-k8s/dynamodb-controller/releases/latest" | grep '"tag_name":' | cut -d'"' -f4)

helm install --create-namespace -n ack-system oci://public.ecr.aws/aws-controllers-k8s/dynamodb-chart "--version=${RELEASE_VERSION_DYNAMODB_ACK}" --generate-name --set=aws.region=us-east-1
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Now, it's time to configure the IAM permissions for the controller to invoke Lambda, DynamoDB and API Gateway.

Configure IAM permissions

Create an OIDC identity provider for your cluster

For the below steps, replace the EKS_CLUSTER_NAME and AWS_REGION variables with your cluster name and region.

export EKS_CLUSTER_NAME=demo-eks-cluster    
export AWS_REGION=us-east-1

eksctl utils associate-iam-oidc-provider --cluster $EKS_CLUSTER_NAME --region $AWS_REGION --approve

OIDC_PROVIDER=$(aws eks describe-cluster --name $EKS_CLUSTER_NAME --query "cluster.identity.oidc.issuer" --output text | cut -d '/' -f2- | cut -d '/' -f2-)
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Create IAM roles for your Lambda, API Gateway and DynamoDB ACK service controllers

ACK Lambda controller

Set the following environment variables:

ACK_K8S_SERVICE_ACCOUNT_NAME=ack-lambda-controller
ACK_K8S_NAMESPACE=ack-system
AWS_ACCOUNT_ID=$(aws sts get-caller-identity --query "Account" --output text)
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Create the trust policy for the IAM role:

read -r -d '' TRUST_RELATIONSHIP <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::${AWS_ACCOUNT_ID}:oidc-provider/${OIDC_PROVIDER}"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "${OIDC_PROVIDER}:sub": "system:serviceaccount:${ACK_K8S_NAMESPACE}:${ACK_K8S_SERVICE_ACCOUNT_NAME}"
        }
      }
    }
  ]
}
EOF

echo "${TRUST_RELATIONSHIP}" > trust_lambda.json
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Create the IAM role:

ACK_CONTROLLER_IAM_ROLE="ack-lambda-controller"

ACK_CONTROLLER_IAM_ROLE_DESCRIPTION="IRSA role for ACK lambda controller deployment on EKS cluster using Helm charts"

aws iam create-role --role-name "${ACK_CONTROLLER_IAM_ROLE}" --assume-role-policy-document file://trust_lambda.json --description "${ACK_CONTROLLER_IAM_ROLE_DESCRIPTION}"
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Attach IAM policy to the IAM role:

# we are getting the policy directly from the ACK repo

INLINE_POLICY="$(curl https://raw.githubusercontent.com/aws-controllers-k8s/lambda-controller/main/config/iam/recommended-inline-policy)"

aws iam put-role-policy \
        --role-name "${ACK_CONTROLLER_IAM_ROLE}" \
        --policy-name "ack-recommended-policy" \
        --policy-document "${INLINE_POLICY}"
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Attach ECR permissions to the controller IAM role - these are required since Lambda functions will be pulling images from ECR. Make sure to update the ecr-permissions.json file with the AWS_ACCOUNT_ID and AWS_REGION variables.

aws iam put-role-policy \
        --role-name "${ACK_CONTROLLER_IAM_ROLE}" \
        --policy-name "ecr-permissions" \
        --policy-document file://ecr-permissions.json
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Associate the IAM role to a Kubernetes service account:

ACK_CONTROLLER_IAM_ROLE_ARN=$(aws iam get-role --role-name=$ACK_CONTROLLER_IAM_ROLE --query Role.Arn --output text)

export IRSA_ROLE_ARN=eks.amazonaws.com/role-arn=$ACK_CONTROLLER_IAM_ROLE_ARN
kubectl annotate serviceaccount -n $ACK_K8S_NAMESPACE $ACK_K8S_SERVICE_ACCOUNT_NAME $IRSA_ROLE_ARN
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Repeat the steps for the API Gateway controller.

ACK API Gateway controller

Set the following environment variables:

ACK_K8S_SERVICE_ACCOUNT_NAME=ack-apigatewayv2-controller
ACK_K8S_NAMESPACE=ack-system
AWS_ACCOUNT_ID=$(aws sts get-caller-identity --query "Account" --output text)
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Create the trust policy for the IAM role:

read -r -d '' TRUST_RELATIONSHIP <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::${AWS_ACCOUNT_ID}:oidc-provider/${OIDC_PROVIDER}"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "${OIDC_PROVIDER}:sub": "system:serviceaccount:${ACK_K8S_NAMESPACE}:${ACK_K8S_SERVICE_ACCOUNT_NAME}"
        }
      }
    }
  ]
}
EOF

echo "${TRUST_RELATIONSHIP}" > trust_apigatewayv2.json
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Create the IAM role:

ACK_CONTROLLER_IAM_ROLE="ack-apigatewayv2-controller"

ACK_CONTROLLER_IAM_ROLE_DESCRIPTION="IRSA role for ACK apigatewayv2 controller deployment on EKS cluster using Helm charts"

aws iam create-role --role-name "${ACK_CONTROLLER_IAM_ROLE}" --assume-role-policy-document file://trust_apigatewayv2.json --description "${ACK_CONTROLLER_IAM_ROLE_DESCRIPTION}"
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Attach managed IAM policies to the IAM role:

aws iam attach-role-policy --role-name "${ACK_CONTROLLER_IAM_ROLE}" --policy-arn arn:aws:iam::aws:policy/AmazonAPIGatewayAdministrator
aws iam attach-role-policy --role-name "${ACK_CONTROLLER_IAM_ROLE}" --policy-arn arn:aws:iam::aws:policy/AmazonAPIGatewayInvokeFullAccess
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Associate the IAM role to a Kubernetes service account:

ACK_CONTROLLER_IAM_ROLE_ARN=$(aws iam get-role --role-name=$ACK_CONTROLLER_IAM_ROLE --query Role.Arn --output text)

export IRSA_ROLE_ARN=eks.amazonaws.com/role-arn=$ACK_CONTROLLER_IAM_ROLE_ARN
kubectl annotate serviceaccount -n $ACK_K8S_NAMESPACE $ACK_K8S_SERVICE_ACCOUNT_NAME $IRSA_ROLE_ARN
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Repeat the steps for the DynamoDB controller.

ACK DynamoDB controller

Set the following environment variables:

ACK_K8S_SERVICE_ACCOUNT_NAME=ack-dynamodb-controller
ACK_K8S_NAMESPACE=ack-system
AWS_ACCOUNT_ID=$(aws sts get-caller-identity --query "Account" --output text)
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Create the trust policy for the IAM role:

read -r -d '' TRUST_RELATIONSHIP <<EOF
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::${AWS_ACCOUNT_ID}:oidc-provider/${OIDC_PROVIDER}"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "${OIDC_PROVIDER}:sub": "system:serviceaccount:${ACK_K8S_NAMESPACE}:${ACK_K8S_SERVICE_ACCOUNT_NAME}"
        }
      }
    }
  ]
}
EOF

echo "${TRUST_RELATIONSHIP}" > trust_dynamodb.json
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Create the IAM role:

ACK_CONTROLLER_IAM_ROLE="ack-dynamodb-controller"

ACK_CONTROLLER_IAM_ROLE_DESCRIPTION="IRSA role for ACK dynamodb controller deployment on EKS cluster using Helm charts"

aws iam create-role --role-name "${ACK_CONTROLLER_IAM_ROLE}" --assume-role-policy-document file://trust_dynamodb.json --description "${ACK_CONTROLLER_IAM_ROLE_DESCRIPTION}"
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Attach IAM policy to the IAM role:

# for dynamodb controller, we use the managed policy ARN instead of the inline policy (like we did for Lambda controller)

POLICY_ARN="$(curl https://raw.githubusercontent.com/aws-controllers-k8s/dynamodb-controller/main/config/iam/recommended-policy-arn)"

aws iam attach-role-policy --role-name "${ACK_CONTROLLER_IAM_ROLE}" --policy-arn "${POLICY_ARN}"
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Associate the IAM role to a Kubernetes service account:

ACK_CONTROLLER_IAM_ROLE_ARN=$(aws iam get-role --role-name=$ACK_CONTROLLER_IAM_ROLE --query Role.Arn --output text)

export IRSA_ROLE_ARN=eks.amazonaws.com/role-arn=$ACK_CONTROLLER_IAM_ROLE_ARN
kubectl annotate serviceaccount -n $ACK_K8S_NAMESPACE $ACK_K8S_SERVICE_ACCOUNT_NAME $IRSA_ROLE_ARN
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Restart ACK controller Deployments and verify the setup

Restart ACK service controller Deployment using the following commands - it will update service controller Pods with IRSA environment variables.
Get list of ACK service controller deployments:

export ACK_K8S_NAMESPACE=ack-system

kubectl get deployments -n $ACK_K8S_NAMESPACE
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Restart Lambda, API Gateway and DynamoDB Deployments:

DEPLOYMENT_NAME_LAMBDA=<enter deployment name for lambda controller>
kubectl -n $ACK_K8S_NAMESPACE rollout restart deployment $DEPLOYMENT_NAME_LAMBDA

DEPLOYMENT_NAME_APIGW=<enter deployment name for apigw controller>
kubectl -n $ACK_K8S_NAMESPACE rollout restart deployment $DEPLOYMENT_NAME_APIGW

DEPLOYMENT_NAME_DYNAMODB=<enter deployment name for dynamodb controller>
kubectl -n $ACK_K8S_NAMESPACE rollout restart deployment $DEPLOYMENT_NAME_DYNAMODB
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List Pods for these Deployments. Verify that the AWS_WEB_IDENTITY_TOKEN_FILE and AWS_ROLE_ARN environment variables exist for your Kubernetes Pod using the following commands:

kubectl get pods -n $ACK_K8S_NAMESPACE

LAMBDA_POD_NAME=<enter Pod name for lambda controller>
kubectl describe pod -n $ACK_K8S_NAMESPACE $LAMBDA_POD_NAME | grep "^\s*AWS_"

APIGW_POD_NAME=<enter Pod name for apigw controller>
kubectl describe pod -n $ACK_K8S_NAMESPACE $APIGW_POD_NAME | grep "^\s*AWS_"

DYNAMODB_POD_NAME=<enter Pod name for dynamodb controller>
kubectl describe pod -n $ACK_K8S_NAMESPACE $DYNAMODB_POD_NAME | grep "^\s*AWS_"
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Now that the ACK service controller have been setup and configured, you can create AWS resources!

Create API Gateway resources, DynamoDB table and deploy the Lambda function

Create API Gateway resources

In the file apigw-resources.yaml, replace the AWS account ID in the integrationURI attribute for the Integration resource. This is what the ACK manifest for API Gateway resources (API, Integration and Stage) looks like:

apiVersion: apigatewayv2.services.k8s.aws/v1alpha1
kind: API
metadata:
  name: ack-demo-apigw-httpapi
spec:
  name: ack-demo-apigw-httpapi
  protocolType: HTTP

---

apiVersion: apigatewayv2.services.k8s.aws/v1alpha1
kind: Integration
metadata:
  name: ack-demo-apigw-integration
spec:
  apiRef:
    from:
      name: ack-demo-apigw-httpapi
  integrationType: AWS_PROXY
  integrationMethod: POST
  integrationURI: arn:aws:lambda:us-east-1:AWS_ACCOUNT_ID:function:demo-dynamodb-func-ack
  payloadFormatVersion: "2.0"

---


apiVersion: apigatewayv2.services.k8s.aws/v1alpha1
kind: Stage
metadata:
  name: demo-stage
spec:
  apiRef:
    from:
      name: ack-demo-apigw-httpapi
  stageName: demo-stage
  autoDeploy: true
  description: "demo stage for http api"
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Create the API Gateway resources (API, Integration and Stage) using the following command:

kubectl apply -f apigw-resources.yaml
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Create DynamoDB table

This is what the ACK manifest for DynamoDB table looks like:

apiVersion: dynamodb.services.k8s.aws/v1alpha1
kind: Table
metadata:
  name: user
  annotations:
   services.k8s.aws/region: us-east-1
spec:
  attributeDefinitions:
    - attributeName: email
      attributeType: S
  billingMode: PAY_PER_REQUEST
  keySchema:
    - attributeName: email
      keyType: HASH
  tableName: user
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You can replace the us-east-1 region with your preferred region.

Create a table (named user) using the following command:

kubectl apply -f dynamodb-table.yaml

# list the tables
kubectl get tables
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Build function binary and create docker image

GOARCH=amd64 GOOS=linux go build -o main main.go

aws ecr-public get-login-password --region us-east-1 | docker login --username AWS --password-stdin public.ecr.aws

docker build -t demo-apigw-dynamodb-func-ack .
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Create a private ECR repository, tag and push the Docker image to ECR:

AWS_ACCOUNT_ID=$(aws sts get-caller-identity --query "Account" --output text)

aws ecr get-login-password --region us-east-1 | docker login --username AWS --password-stdin $AWS_ACCOUNT_ID.dkr.ecr.us-east-1.amazonaws.com

aws ecr create-repository --repository-name demo-apigw-dynamodb-func-ack --region us-east-1

docker tag demo-apigw-dynamodb-func-ack:latest $AWS_ACCOUNT_ID.dkr.ecr.us-east-1.amazonaws.com/demo-apigw-dynamodb-func-ack:latest
docker push $AWS_ACCOUNT_ID.dkr.ecr.us-east-1.amazonaws.com/demo-apigw-dynamodb-func-ack:latest
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Create an IAM execution Role for the Lambda function and attach the required policies:

export ROLE_NAME=demo-apigw-dynamodb-func-ack-role

ROLE_ARN=$(aws iam create-role \
        --role-name $ROLE_NAME \
        --assume-role-policy-document '{"Version": "2012-10-17","Statement": [{ "Effect": "Allow", "Principal": {"Service": "lambda.amazonaws.com"}, "Action": "sts:AssumeRole"}]}' \
        --query 'Role.[Arn]' --output text)

aws iam attach-role-policy --role-name $ROLE_NAME --policy-arn arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole
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Since the Lambda function needs to write data to DynamoDB let's add the following policy to the IAM role:

aws iam put-role-policy \
        --role-name "${ROLE_NAME}" \
        --policy-name "dynamodb-put" \
        --policy-document file://dynamodb-put.json
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Create the Lambda function

Update function.yaml file with the following info:

  • imageURI - the URI of the Docker image that you pushed to ECR e.g. <AWS_ACCOUNT_ID>.dkr.ecr.us-east-1.amazonaws.com/demo-apigw-dynamodb-func-ack:latest
  • role - the ARN of the IAM role that you created for the Lambda function e.g. arn:aws:iam::<AWS_ACCOUNT_ID>:role/demo-apigw-dynamodb-func-ack-role

This is what the ACK manifest for the Lambda function looks like:

apiVersion: lambda.services.k8s.aws/v1alpha1
kind: Function
metadata:
 name: demo-apigw-dynamodb-func-ack
 annotations:
   services.k8s.aws/region: us-east-1
spec:
 architectures:
  - x86_64
 name: demo-apigw-dynamodb-func-ack
 packageType: Image
 code:
     imageURI: AWS_ACCOUNT_ID.dkr.ecr.us-east-1.amazonaws.com/demo-apigw-dynamodb-func-ack:latest
 environment:
    variables:
      TABLE_NAME: user
 role: arn:aws:iam::AWS_ACCOUNT_ID:role/demo-apigw-dynamodb-func-ack-role
 description: A function created by ACK lambda-controller
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To create the Lambda function, run the following command:

kubectl create -f function.yaml

# list the function
kubectl get functions
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Add API Gateway trigger configuration

Here is an example using AWS Console - Open the Lambda function in the AWS Console and click on the Add trigger button. Select API Gateway as the trigger source, select the existing API and click on the Add button.

Image description

Now you are ready to try out the end to end solution!

Test the application

Get the API Gateway endpoint:

export API_NAME=ack-demo-apigw-httpapi
export STAGE_NAME=demo-stage

export URL=$(kubectl get api/"${API_NAME}" -o=jsonpath='{.status.apiEndpoint}')/"${STAGE_NAME}"/demo-apigw-dynamodb-func-ack"
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Invoke the API Gateway endpoint:

curl -i -X POST -H 'Content-Type: application/json' -d '{"email":"user1@foo.com","name":"user1"}' $URL

curl -i -X POST -H 'Content-Type: application/json' -d '{"email":"user2@foo.com","name":"user2"}' $URL

curl -i -X POST -H 'Content-Type: application/json' -d '{"email":"user3@foo.com","name":"user3"}' $URL

curl -i -X POST -H 'Content-Type: application/json' -d '{"email":"user4@foo.com","name":"user4"}' $URL
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The Lambda function should be invoked and the data should be written to the DynamoDB table. Check the DynamoDB table using the CLI (or AWS console):

aws dynamodb scan --table-name user
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Clean up

After you have explored the solution, you can clean up the resources by running the following commands:

Delete API Gateway resources, DynamoDB table and the Lambda function:

kubectl delete -f apigw-resources.yaml
kubectl delete -f function.yaml
kubectl delete -f dynamodb-table.yaml
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To uninstall the ACK service controllers, run the following commands:

export ACK_SYSTEM_NAMESPACE=ack-system

helm ls -n $ACK_SYSTEM_NAMESPACE

helm uninstall -n $ACK_SYSTEM_NAMESPACE <enter name of the apigw chart>
helm uninstall -n $ACK_SYSTEM_NAMESPACE <enter name of the lambda chart>
helm uninstall -n $ACK_SYSTEM_NAMESPACE <enter name of the dynamodb chart>
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Conclusion and next steps

In this post, we have seen how to use AWS Controllers for Kubernetes to create a Lambda function, API Gateway integration, DynamoDB table and wire them together to deploy a solution. All of this (almost) was done using Kubernetes! I encourage you to try out other AWS services supported by ACK - here is a complete list.

Happy Building!

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