Create AWS Load Balancer Controller Ingress With CDK8S

This content originally appeared on DEV Community and was authored by Vu Dao

? What is AWS Load Balancer Controller

The AWS Load Balancer Controller manages AWS Elastic Load Balancers for a Kubernetes cluster. The controller provisions the following resources.
- An AWS Application Load Balancer (ALB) when you create a Kubernetes Ingress.
- An AWS Network Load Balancer (NLB) when you create a Kubernetes Service of type LoadBalancer.

? Install AWS Load Balancer Controller as the ingress controller

Pre-requiste: EKS cluster
In order for the Ingress resource to work, the cluster must have an ingress controller running. Unlike other types of controllers which run as part of the kube-controller-manager binary, Ingress controllers are not started automatically with a cluster.
Using hlem to install

[ec2-user@eks-ctl dist]$ helm repo add eks https://aws.github.io/eks-charts
"eks" has been added to your repositories

export VPC_ID=$(aws eks describe-cluster --name eks-dev --query "cluster.resourcesVpcConfig.vpcId" --output text --region ap-northeast-2)

[ec2-user@eks-ctl dist]$ helm repo list
NAME    URL
eks     https://aws.github.io/eks-charts

[ec2-user@eks-ctl dist]$ helm repo update
Hang tight while we grab the latest from your chart repositories...
...Successfully got an update from the "eks" chart repository
Update Complete. ⎈Happy Helming!⎈

helm upgrade -i aws-load-balancer-controller \
    eks/aws-load-balancer-controller \
    -n kube-system \
    --set clusterName=eks-dev \
    --set serviceAccount.create=false \
    --set serviceAccount.name=aws-load-balancer-controller \
    --set image.tag="${LBC_VERSION}" \
    --set region=ap-northeast-2 \
    --set vpcId=${VPC_ID}

Release "aws-load-balancer-controller" does not exist. Installing it now.
NAME: aws-load-balancer-controller
LAST DEPLOYED: Sun Jun  6 10:44:19 2021
NAMESPACE: kube-system
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
AWS Load Balancer controller installed!

[ec2-user@eks-ctl dist]$ kubectl get deployment -n kube-system aws-load-balancer-controller
NAME                           READY   UP-TO-DATE   AVAILABLE   AGE
aws-load-balancer-controller   0/2     2            0           8s

[ec2-user@eks-ctl dist]$ kubectl get po -n kube-system 
NAME                                            READY   STATUS    RESTARTS   AGE
aws-load-balancer-controller-85847bc9bd-fjdwf   1/1     Running   0          20s
aws-load-balancer-controller-85847bc9bd-gsctk   1/1     Running   0          20s

? Create AWS ALB IAM Role Service Account Using CDK

Pre-requisite: EKS cluster with OpenID connect, IAM identity provider (Ref to Using IAM Service Account Instead Of Instance Profile For EKS Pods for how to)
First create the IAM role which is federated by IAM identiy provider and assumed by sts:AssumeRoleWithWebIdentity, then attach policy to provide proper permission for the role. Brief of CDK code in python3:
- iam_oic is the stack of creating IAM identity provider which is used OIDC as provider, open_id_connect_provider_arn is its ARN attribute from the stack.
- Policy is created from iam_policy.json

from constructs import Construct
from aws_cdk.aws_s3_assets import Asset
from aws_cdk import (
    App, Stack, CfnJson,
    aws_iam as iam
)
import re, os


class IamOICProvider(Stack):
    def __init__(f, scope: Construct, construct_id: str, eks_cluster, env, **kwargs) -> None:
        super().__init__(scope, construct_id, env=env, **kwargs)

        oidc_url = eks_cluster.cluster_open_id_connect_issuer_url
        iam_oic = iam.OpenIdConnectProvider(
            f, construct_id,
            url=oidc_url,
            client_ids=['sts.amazonaws.com']
        )
        oidc_arn = iam_oic.open_id_connect_provider_arn
        oidc_provider = re.sub("https://", "", oidc_url)

        def string_like(name_space, sa_name):
            string_like = CfnJson(
                f, f'JsonCondition{sa_name}',
                value={
                    f'{oidc_provider}:sub': f'system:serviceaccount:{name_space}:{sa_name}',
                    f'{oidc_provider}:aud': 'sts.amazonaws.com'
                }
            )
            return string_like

        alb_controller_role = iam.Role(
            f, 'AlbControllerRole',
            role_name='eks-aws-load-balancer-controller-sa',
            assumed_by=iam.FederatedPrincipal(
                federated=f'{iam_oic.open_id_connect_provider_arn}',
                conditions={'StringEquals': string_like('kube-system', 'aws-load-balancer-controller')},
                assume_role_action='sts:AssumeRoleWithWebIdentity'
            )
        )
        alb_controller_role.add_managed_policy(
            iam.ManagedPolicy.from_managed_policy_name(f, "EksAWSLoadBalancerController",
                                                       managed_policy_name='EksAWSLoadBalancerController')
        )
        alb_controller_role.add_managed_policy(
            iam.ManagedPolicy.from_managed_policy_name(f, "EksAWSLoadBalancerControllerAdditional",
                                                       managed_policy_name='EksAWSLoadBalancerControllerAdditional')
        )

Annotate the IRSA to aws-load-balancer-controller service account

$ kubectl annotate serviceaccount -n kube-system aws-load-balancer-controller eks.amazonaws.com/role-arn=arn:aws:iam::123456789012:role/eks-aws-load-balancer-controller-sa

Double check the IAM role at the Trust relationships to ensure correct OIDC url and Condition

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Federated": "arn:aws:iam::123456789012:oidc-provider/oidc.eks.ap-northeast-2.amazonaws.com/id/<OIDC_PROVIDER_ID>"
      },
      "Action": "sts:AssumeRoleWithWebIdentity",
      "Condition": {
        "StringEquals": {
          "oidc.eks.ap-northeast-2.amazonaws.com/id/<OIDC_PROVIDER_ID>:sub": "system:serviceaccount:kube-system:aws-load-balancer-controller",
          "oidc.eks.ap-northeast-2.amazonaws.com/id/<OIDC_PROVIDER_ID>:aud": "sts.amazonaws.com"
        }
      }
    }
  ]
}

Check the SA

[ec2-user@eks-ctl ~]$ kubectl describe sa -n kube-system aws-load-balancer-controller 
Name:                aws-load-balancer-controller
Namespace:           kube-system
Labels:              app.kubernetes.io/component=controller
                     app.kubernetes.io/name=aws-load-balancer-controller
Annotations:         eks.amazonaws.com/role-arn: arn:aws:iam::123456789012:role/eks-aws-load-balancer-controller-sa
                     kubectl.kubernetes.io/last-applied-configuration:
                       {"apiVersion":"v1","kind":"ServiceAccount","metadata":{"annotations":{"eks.amazonaws.com/role-arn":"arn:aws:iam::123456789012:role/eks...
Image pull secrets:  <none>
Mountable secrets:   aws-load-balancer-controller-token-gjsc2
Tokens:              aws-load-balancer-controller-token-gjsc2
Events:              <none>

? Create Ingress Using CDK8S

Pre-requiste: ACM cert to attach to the ALB
cdk8s example
Some notes: All ingresses should be in a group so we only need one AWS ALB. Group order shoulb be taken care to prioritize the rule with host conditions
Source: https://github.com/vumdao/aws-eks-the-hard-way/tree/master/aws-alb-controller/ingress

? Apply the ingress yaml files

After applying the yaml files, check all ingress

[ec2-user@eks-ctl ~]$ kubectl get ingress -A
NAMESPACE   NAME                     CLASS    HOSTS                       ADDRESS                                                           PORTS   AGE
argocd      argocd                   <none>   argocd.cloudopz.co          k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      14d
dev         app                      <none>   *                           k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      18d
dev         backend                  <none>   *                           k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      8d
dev         frontend                 <none>   *                           k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      8d
dev         dev-alb                  <none>   *                           k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      18d
grafana     grafana                  <none>   grafana.cloudopz.co         k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      7d3h
logging     kibana                   <none>   kibana.cloudopz.co          k8s-dev-06fc49d1xx-1234567890.ap-northeast-2.elb.amazonaws.com    80      25h

Check aws-load-balancer-controller if your ingress does not work

kubectl logs -f --tail=100 -n kube-system -l app.kubernetes.io/name=aws-load-balancer-controller

? Create Route53 records for the domains using CDK

In order to automate detect the AWS k8s ALB, we can use lookup function and base on the tag the AWS ALB controller created ingress.k8s.aws/stack: <group>

import re
import os
from constructs import Construct
import boto3
from aws_cdk import (
    App, Stack, Environment, Tags, CfnTag, Duration,
    aws_elasticloadbalancingv2 as elbv2,
    aws_route53 as _route53,
)


class Route53Stack(Stack):

    def __init__(self, scope: Construct, id: str, env, **kwargs) -> None:
        super().__init__(scope, id, env=env, **kwargs)

        def cname_record(record_name, hosted_zone):
            _route53.CnameRecord(
                self, 'Route53Cname',
                domain_name=alb_dns,
                record_name=record_name,
                zone=hosted_zone,
                ttl=Duration.minutes(1)
            )

        alb = elbv2.ApplicationLoadBalancer.from_lookup(
            self, "AlbIngress",
            load_balancer_tags={'ingress.k8s.aws/stack': 'dev'}
        )
        alb_dns = alb.load_balancer_dns_name

        dev_hosted_zone = 'Z88PZ8J8P8RXXX'

        hz = _route53.HostedZone.from_hosted_zone_attributes(
            self, id="HostedZone", hosted_zone_id=dev_hosted_zone, zone_name='cloudopz.co')

        records = ['dev.cloudopz.co', 'akhq.cloudopz.co', 'argocd.cloudopz.co',
                   'grafana.cloudopz.co', 'kibana.cloudopz.co']
        for record in records:
            cname_record(record, hz)

? Conclusion

Keywords: IRSA, AWS ALB controller, ingress, cdk and cdk8s
If we change order of the ingress group, it might make ALB downtime a little bit to re-generate the rules.

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vumdao / vumdao

This content originally appeared on DEV Community and was authored by Vu Dao

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