How to create VPC that can be shared across stacks? - aws-cdk

Question

I am trying to wrap my head around how to create a reusable VPC that can be used across multiple stacks using AWS CDK. I want to be able to create different stack per project and then be able to import the VPC that should be assigned to the different stacks. I also want to create this using a good structure where I can deploy different stacks at different times (meaning: I do not want to deploy all stacks at once).
I have tried the following approach but this will create a new VPC per stack which is not what I want to achieve, instead I would like to create my VPC once and then if it already exists it will simply reuse the previous created.
app.ts
import cdk = require('#aws-cdk/core');
import { Stack1 } from '../lib/stack1';
import { Stack2 } from '../lib/stack2';
const app = new cdk.App();
new Stack1(app, "Stack1");
new Stack2(app, "Stack2");
stack1.ts
import cdk = require('#aws-cdk/core');
import { Configurator } from './configurators/configurator'
export class Stack1 extends cdk.Stack {
constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
super(scope, id, props);
const configurator = new Configurator(scope, "Stack1");
// later reuse vpc from configurator using configurator.vpc
}
}
stack2.ts
import cdk = require('#aws-cdk/core');
import { Configurator } from './configurators/configurator'
export class Stack2 extends cdk.Stack {
constructor(scope: cdk.App, id: string, props?: cdk.StackProps) {
super(scope, id, props);
const configurator = new Configurator(scope, "Stack2");
// later reuse vpc from configurator using configurator.vpc
}
}
configurator.ts
import cdk = require('#aws-cdk/core');
import ec2 = require("#aws-cdk/aws-ec2");
export class Configurator {
vpc: ec2.Vpc;
constructor(scope: cdk.Construct, name: string) {
this.vpc = new ec2.Vpc(scope, "MyVPC", {
maxAzs: 3
});
}
}
After doing
cdk synth
cdk deploy Stack1
cdk deploy Stack2
This will create 2 VPCs and not reusing 1 VPC as I would like. I will deploy the stacks to same account and region.
How can I change my approach in order to achieve the output I am looking for? I want to be able to deploy my stacks independently of each other.

Answer 1

If you intend to reuse the VPC in different stacks, I'd recommend placing it in a separate stack, since your VPC stack will have a different lifecycle than your application stacks.
Here's what I'd do. I hope you don't mind a bit of Python :)
First, define your VPC in VpcStack:
class VpcStack(core.Stack):
def __init__(self, app: core.App, id: str, **kwargs) -> None:
super().__init__(app, id, **kwargs)
aws_ec2.Vpc(self, 'MyVPC', max_azs=3)
Then look it up in another stack:
class Stack1(core.Stack):
def __init__(self, app: core.App, id: str, **kwargs) -> None:
super().__init__(app, id, **kwargs)
# Lookup the VPC named 'MyVPC' created in stack 'vpc-stack'
my_vpc = aws_ec2.Vpc.from_lookup(self, 'MyVPC', vpc_name=f'vpc-stack/MyVPC')
# You can now use the VPC in ECS cluster, etc.
And this would be your cdk_app.py:
app = core.App()
vpc = VpcStack(app, 'vpc-stack')
stack1 = Stack1(app, 'stack1')

Answer 2

I tried 0x32e0edfb answer and got some problem.
so I fix like this.
VPC Stack
class VpcStack(core.Stack):
def __init__(self, scope: core.Construct, id: str, **kwargs) -> None:
super().__init__(scope, id, **kwargs)
self.eks_vpc = ec2.Vpc(self, 'eks-vpc',
cidr='10.1.0.0/16',
max_azs=2
)
share VPC to other Stack
class EksClusterStack(core.Stack):
def __init__(self, scope: core.Construct, id: str, props: ec2.Vpc, **kwargs) -> None:
super().__init__(scope, id, **kwargs)
cluster = eks.Cluster(self, 'eks-control-plane',
vpc=props,
default_capacity=0
)
and then app.py file
app = core.App()
vpc_stack = VpcStack(app, 'vpc-stack')
eks_cluster_stack = EksClusterStack(app, 'eks-cluster', vpc_stack.eks_vpc)
eks_cluster_stack.add_dependency(vpc_stack)
app.synth()
from_lookup is much better used on already existing VPC.
so I choose to use share-vpcs to share VPC information.
from_lookup only does the API call once - then, the data is cached in the cdk.context.json file, which should be committed to source control
That problem was when I recreating the same VPC.
cdk.context.json didn't update to lasted version. So when I use from_lookup always get old vpc-id.
I need to use cdk context --clear command and then deploy again. cdk.context.json would get lasted version vpc-id.
Finally, it can work properly on from_lookup method.
ref:
https://github.com/aws/aws-cdk/blob/master/packages/%40aws-cdk/aws-eks/test/integ.eks-kubectl.lit.ts
https://docs.aws.amazon.com/cdk/latest/guide/context.html