Abstract

• In the world of Infrastructure as code (IaC) there are many tools that support us to create AWS resources quickly such as CDK, Pulumi, and Terraform. Today I introduce AWS Controllers for Kubernetes (ACK)

• AWS Controllers for Kubernetes (ACK) lets you define and use AWS service resources directly from Kubernetes. With ACK, you can take advantage of AWS-managed services for your Kubernetes applications without needing to define resources outside of the cluster or run services that provide supporting capabilities like databases or message queues within the cluster.

• This post provides step-by-step to create AWS RDS postgres in private VPC using ACK and then accessing the database to prove it works.

Table Of Contents

• Introduction of ACK

• Install the ACK service controller for RDS

• Create ACK ServiceAccount base on IRSA

• Create RDS secret keys

• Create subnet group

• Create security group to allow traffic from EKS pods to the RDS

• Create DBInstance

• Access RDS through EKS pod

• Clean-up workspace

• Conclusion

🚀 Introduction of ACK

• Overview

• How it works

  

• AWS service supported

• When to use ACK? Read here

🚀 Install the ACK service controller for RDS

• Pre-requisite:

  • EKS cluster

  • OIDC for IRSA

  • IAM for service account (IRSA) - Checkout Using IAM Service Account Instead Of Instance Profile For EKS Pods for how-to.

• Install ACK for RDS

    ⚡ $ export HELM_EXPERIMENTAL_OCI=1
    ⚡ $ helm pull oci://public.ecr.aws/aws-controllers-k8s/rds-chart --version=v0.0.17
    ⚡ $ tar xf rds-chart-v0.0.17.tgz
    ⚡ $ helm install rds-chart --generate-name --set=aws.region=ap-northeast-2
  

🚀 Create ACK ServiceAccount base on IRSA

• This step requires IAM role for service account here is ACK RDS. Note that the role needs permission to manage RDS resources. We can limit permission by restricting resources. And to protect the resource from incidents of deleteing the DBInstance (describe later), we can set Deny action of rds:DeleteDBInstance

    {
        "Version": "2012-10-17",
        "Statement": [
            {
                "Condition": {
                    "StringEquals": {
                        "aws:RequestedRegion": "ap-northeast-2"
                    }
                },
                "Action": "rds:*",
                "Resource": "arn:aws:rds:ap-northeast-2:123456789012:*",
                "Effect": "Allow",
                "Sid": "CreateRds"
            },
            {
                "Action": "rds:DeleteDBInstance",
                "Resource": "*",
                "Effect": "Deny",
                "Sid": "DenyDeleteRds"
            }
        ]
    }
  

• Generate SA yaml and update IRSA to apply, replace the IAM ARN role with yours.

  ack-sa.yaml

      apiVersion: v1
      kind: ServiceAccount
      metadata:
      labels:
          app.kubernetes.io/component: controller
          app.kubernetes.io/name: ack-rds-controller
      name: ack-rds-controller
      annotations:
          eks.amazonaws.com/role-arn: arn:aws:iam::123456789012:role/ack-rds-controller-d1
  

• Apply the manifest

    kf apply -f ack-sa.yaml
  

🚀 Create RDS secret keys

• The best practice is to protect the RDS user's password

    export RDS_DB_USERNAME=rds_username
    export RDS_DB_PASSWORD=rds_password
  
    kubectl create secret generic rds-postgresql-user-creds \
      --from-literal=username="${RDS_DB_USERNAME}" \
      --from-literal=password="${RDS_DB_PASSWORD}"
  

🚀 Create a subnet group

• The subnet group contains all subnets of EKS private VPC

• Get subnets from EKS VPC, replace the VPC ID and the region with yours

    EKS_SUBNET_IDS=$(aws ec2 describe-subnets --filters "Name=vpc-id,Values=vpc-0eb6477bf2c8430cd" --query 'Subnets[*].SubnetId' --output text --region ap-northeast-2)
  

• Generate yaml file inherit ${EKS_SUBNET_IDS} above

      cat <<-EOF > ack/ack-rds-subnet-groups.yaml
      apiVersion: rds.services.k8s.aws/v1alpha1
      kind: DBSubnetGroup
      metadata:
      name: rds-postgresql-subnet-group
      spec:
      name: rds-postgresql-subnet-group
      description: RDS for app in EKS
      subnetIDs:
      $(printf "    - %s\n" ${EKS_SUBNET_IDS})
      tags:
          - key: stage
            value: development
          - key: owner
            value: dev
      EOF
  

• Apply the manifest

    kf apply -f ack/ack-rds-subnet-groups.yaml
  

🚀 Create security group to allow traffic from EKS pods to the RDS

• First, we create an SG in the EKS VPC to attach to the RDS, replace the VPC ID with your EKS VPC ID and the appropriate region

    RDS_SECURITY_GROUP_ID=$(aws ec2 create-security-group \
           --group-name rds-postgres-sg \
           --description "SG to allow traffic from EKS pod to RDS" \
           --vpc-id vpc-0eb6477bf2c8430cd \
           --output text --region ap-northeast-2
         )
  

• Then we need to allow traffic from EKS worker nodes. There are two ways

  1. In RDS SG, allow traffic from CIDR range of the EKS VPC

     • Get CIDR range of EKS VCP using the command line

         EKS_CIDR_RANGE=$(aws ec2 describe-vpcs --vpc-ids vpc-0eb6477bf2c8430cd --query 'Vpcs[].CidrBlock' --output text --region ap-northeast-2)
       

     • Create ingress in the SG to allow traffic from the above CIDR

          aws ec2 authorize-security-group-ingress \
          --group-id "${RDS_SECURITY_GROUP_ID}" \
          --protocol tcp \
          --port 5432 \
          --cidr "${EKS_CIDR_RANGE}" \
          --region ap-northeast-2
       

  2. In RDS SG, allow traffic from the security group which is attached to all EKS nodes (in general, traffic is allowed from the network interfaces that are associated with the source security group for the specified protocol and port, read more from Understand Pods communication at Security groups for your VPC specifying a security group as the source for a rule)

🚀 Create DBInstance

• Create DBInstance manifest, replace security group ID in vpcSecurityGroupIDs with the one you created in the previous step RDS_SECURITY_GROUP_ID. Here we select RDS instance type db.t3.micro as it is free tier, master user and password maps with the RDS secret keys created in previous step, engine: postgres version 10ack/ack-rds-postgresql.yaml

    apiVersion: rds.services.k8s.aws/v1alpha1
    kind: DBInstance
    metadata:
      name: "rds-postgresql-dev"
    spec:
      allocatedStorage: 20
      autoMinorVersionUpgrade: true
      backupRetentionPeriod: 7
      dbInstanceClass: db.t3.micro
      dbInstanceIdentifier: "rds-postgresql-dev"
      dbSubnetGroupName: rds-postgresql-subnet-group
      engine: postgres
      engineVersion: "10"
      masterUsername: "rds_user"
      masterUserPassword:
        namespace: default
        name: rds-postgresql-user-creds
        key: password
      multiAZ: true
      publiclyAccessible: false
      storageEncrypted: true
      storageType: gp2
      vpcSecurityGroupIDs:
        - sg-009c3a2658d1f7165
      tags:
        - key: stage
          value: development
        - key: owner
          value: dev
  

• Apply the yaml

    kf apply -f ack/ack-rds-postgresql.yaml
  

• Check created DBInstance

    ⚡ $ kf get DBInstance
    NAME                 AGE
    rds-postgresql-dev   1h
  

  

🚀 Access RDS through EKS pod

• This step proves RDS works well and EKS pods in private VPC can read/write to the RDS using master user

• Build postgresql-client docker image and push it to ECR or any container image repository

    FROM alpine:3
    RUN apk add --no-cache postgresql-client
    CMD while true; do sleep 5; echo psql-client; done
  

• Create postgresql client deployment psql-client.yaml

    apiVersion: apps/v1
    kind: Deployment
    metadata:
      labels:
        app: psql-client
      name: psql-client
    spec:
      replicas: 1
      selector:
        matchLabels:
          app: psql-client-deployment
      template:
        metadata:
          labels:
            app: psql-client-deployment
        spec:
          containers:
            - image: 123456789012.dkr.ecr.ap-northeast-2.amazonaws.com/psql/client:latest
              name: psql-client
  

• Apply the deployment and then get the pod

    ~ $ kf apply -f ack/psql-client.yaml
    deployment.apps/psql-client created
  
    ~ $ kf get pod
    NAME                                    READY   STATUS    RESTARTS   AGE
    psql-client-9d45f759-8swtr              1/1     Running   0          44m
  

• Go into the pod to access RDS, get RDS private endpoint in the console or use AWS CLI or using kubectl

    ~ $ aws rds describe-db-instances --db-instance-identifier rds-postgresql-dev --region ap-northeast-2 --query 'DBInstances[0].Endpoint.Address'
    "rds-postgresql-dev.xxxxxxxxxxxx.ap-northeast-2.rds.amazonaws.com"
  
    ~ $ kubectl get dbinstance rds-postgresql-dev -o jsonpath='{.status.endpoint.address}'
    "rds-postgresql-dev.xxxxxxxxxxxx.ap-northeast-2.rds.amazonaws.com"
  
    ~ $ kf exec -it psql-client-9d45f759-8swtr -- sh
    / # psql -h rds-postgresql-dev.xxxxxxxxxxxx.ap-northeast-2.rds.amazonaws.com -U rds_user -d postgres
    postgres=> \du
                                                                      List of roles
          Role name      |                         Attributes                         |                          Member of
      --------------------+------------------------------------------------------------+-------------------------------------------------------------
      rds_user           | Create role, Create DB                                    +| {rds_superuser}
                         | Password valid until infinity                              |
      rds_ad             | Cannot login                                               | {}
      rds_iam            | Cannot login                                               | {}
      rds_password       | Cannot login                                               | {}
      rds_replication    | Cannot login                                               | {}
      rds_superuser      | Cannot login                                               | {pg_monitor,pg_signal_backend,rds_replication,rds_password}
      rdsadmin           | Superuser, Create role, Create DB, Replication, Bypass RLS+| {}
                          | Password valid until infinity                              |
      rdsrepladmin       | No inheritance, Cannot login, Replication                  | {}
  
    postgres=> CREATE DATABASE "rds-test";
    CREATE DATABASE
  
    postgres=> \l rds-test
                                        List of databases
      Name   |       Owner        | Encoding |   Collate   |    Ctype    | Access privileges
    ----------+--------------------+----------+-------------+-------------+-------------------
    rds-test | rds_user | UTF8     | en_US.UTF-8 | en_US.UTF-8 |
    (1 row)
  

🚀 Clean-up workspace

• Delete DBInstance, note that if you deny rds:DeleteDBInstance in ACK role to protect your RDS then this step requires more action such as remove the deny or delete RDS manually then forcing delete DBInstance. Here assume ACK RDS role has the permission of deleting the RDS

    ⚡ $ kf delete DBInstance rds-postgresql-dev
    dbinstance.rds.services.k8s.aws "rds-postgresql-dev" deleted
  

• Delete psql-client deployment

    ⚡ $ kf delete -f ack/psql-client.yaml
    deployment.apps "psql-client" deleted
  

• Delete RDS secret key

    ⚡ $ kf delete secret rds-postgresql-user-creds
    secret "rds-postgresql-user-creds" deleted
  

• Delete RDS security group

    ⚡ $ aws ec2 delete-security-group --group-id sg-009c3a2658d1f7165 --region ap-northeast-2
  

• Uninstall ACK RDS

    ⚡ $ helm list
    NAME                    NAMESPACE       REVISION        UPDATED                                 STATUS          CHART                   APP VERSION
    rds-chart-1648053478    default         1               2022-03-23 23:38:11.397906502 +0700 +07 deployed        rds-chart-v0.0.17       v0.0.17
  
    ⚡ $ helm uninstall rds-chart-1648053478
    release "rds-chart-1648053478" uninstalled
  

• Finally, delete the IRSA for ACK RDS

    ⚡ $ cdk destroy AckControllerSA --profile vc-mfa
    Are you sure you want to delete: AckControllerSA (y/n)? y
    AckControllerSA: destroying...
  
    ✅  AckControllerSA: destroyed
  

🚀 Conclusion

• Using ACK to create AWS resources is a big plus for those ones love managing AWS resources through k8s manifests within the EKS cluster

• We can combine cdk8s to create ACK yaml files

References:

• Deploy Amazon RDS databases for applications in Kubernetes