create or import existing EKS cluster in AWS CDK

main.ts

import cdk = require('@aws-cdk/core');
import eks = require('@aws-cdk/aws-eks');
import ec2 = require('@aws-cdk/aws-ec2');
import iam = require('@aws-cdk/aws-iam');
import { Stack } from '@aws-cdk/core';

const DEFAULT_CLUSTER_VERSION = '1.16'

export class EksStack extends cdk.Stack {
  constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
    super(scope, id, props);
    
 
    // use an existing vpc or create a new one
    const vpc = this.node.tryGetContext('use_default_vpc') === '1' ?
      ec2.Vpc.fromLookup(this, 'Vpc', { isDefault: true }) :
      this.node.tryGetContext('use_vpc_id') ?
        ec2.Vpc.fromLookup(this, 'Vpc', { vpcId: this.node.tryGetContext('use_vpc_id') }) :
        new ec2.Vpc(this, 'Vpc', { maxAzs: 3, natGateways: 1 });

    const clusterVersion = this.node.tryGetContext('cluster_version') ?? DEFAULT_CLUSTER_VERSION

    const mastersRole = new iam.Role(this, 'AdminRole', {
      assumedBy: new iam.AccountRootPrincipal()
    });

    // this creates a new cluster
    const cluster = new eks.Cluster(this, 'EKSCluster', {
      vpc,
      mastersRole,
      version: clusterVersion,
    });

    // to import existing cluster, we need prepare the following info
    const clusterName = this.node.tryGetContext('clusterName') ?? process.env.clusterName ?? undefined;
    const clusterArn = this.node.tryGetContext('clusterArn') ?? process.env.clusterArn ?? undefined;
    const clusterCertificateAuthorityData = this.node.tryGetContext('clusterCertificateAuthorityData') ?? process.env.clusterArn ?? undefined;
    const clusterEndpoint = this.node.tryGetContext('clusterEndpoint') ?? process.env.clusterEndpoint ?? undefined;
    // given your sg is common seperated string like this 'sg-xxxx,sg-xxx,sg-xxxx'
    const securityGroupsString: string = this.node.tryGetContext('securityGroups') ?? process.env.securityGroups ?? undefined;
    const securityGroups = securityGroupsString.split(',').map(sg => ec2.SecurityGroup.fromSecurityGroupId(this, `clusterSg${sg}`, sg) )

    // this import an existing cluster
    const existingCluster = eks.Cluster.fromClusterAttributes(this, 'ExistingCluster', {
      clusterName,
      clusterArn,
      clusterCertificateAuthorityData,
      clusterEndpoint,
      securityGroups, 
      vpc,
    })

    new cdk.CfnOutput(this, 'Region', { value: Stack.of(this).region })
    new cdk.CfnOutput(this, 'ClusterVersion', { value: clusterVersion })
  }
}

So, there is no way to get an existing cluster just from the name?

So, there is no way to get an existing cluster just from the name?

You can, but you won't be able to access many properties. For example, if you don't give an iam.openIdConnectProvider then you will get an error for Cluster.addServiceAccount.