Cdk8s Resources

CDK8S Resources let you programmatically manage and deploy your CDK8S charts. It provides an enhanced way of working with the CDK8S, enabling you to:

• Consistently deploy your charts with built-in rollback mechanisms in case of failure
• Extend your infrastructure-as-code logic (e.g., fetch the IP of a load balancer via SDK calls and update your DNS provider automatically)
• Trigger redeployments in response to specific events

Installation

The CdkResource construct is part of the @orbi-ts/fuel package. You need to install it first:

npm install  @orbi-ts/fuel

Then import it :

import {CdkResource} from "@orbi-ts/fuel

Prerequisite

• kubectl must be installed and properly configured.

Encapsulate a CDK8S chart

Assume you have a CDK8S chart named BasicChart. You wrap it in a CDK8S resource by extending the Cdk8sResource class.

export class BasicResource extends Cdk8sResource {
  StackConstructor = BasicChart ;
}

Outputs

In cdk8s, there is no-built in mechanism as Cloudformation or pulumi output. With orbits, you can mimic this behaviour by defining your own output you can reuse elsewhere. You define your output overriding the setOutput method.

Static output

You can output any values of the object in your stack.

src/cdk/lambda-stack.ts

export class BasicResource extends Cdk8sResource {
  StackConstructor = BasicChart ;
  stack: BasicChart;//for typing purpose

  async setOutput(): Promise<this["IOutput"]> {
    const stack = await this.generateStack();
    return {
      namespace: stack.ns.name,
      cronJobName: stack.cronJob.name
    }
  }
}

This way, you can, for example :

• let the cdk8s generate a namespace name : this.ns = new kplus.Namespace(this, 'my-namespace')
• retrieve and output the generated name :

src/cdk8s/basic-resource.ts

export class BasicResource extends Cdk8sResource {
  StackConstructor = BasicChart ;
  stack: BasicChart;//for typing purpose

  async setOutput(): Promise<this["IOutput"]> {
    const stack = await this.generateStack();
    return {
      namespace: stack.ns.name,
      cronJobName: stack.cronJob.name
    }
  }
}

Dynamic output

You can also want more complex export. For example, you maybe need the ip of your loadbalancer in order to set this IP into your DNS.

• First in your stack, export the load balancer service :

src/cdk8s/basic-resource.ts

this.loadBalancerService = new kplus.Service(this, "load-balancer") 

• Then, in the setOutput(), query the kube api to have the IP address

src/orbits/lambda-resource.ts

export class BasicResource extends CdkResource{
    StackConstructor = BasicChart

    declare IOutput: {
		 publicIPV4: string;
	  };

    async setOutput(){
        const stack = await this.generateStack();
				const apiServiceInfo = await this.kubeApi.coreApi.readNamespacedService({
					name: stack.loadBalancerService.name,
					namespace: stack.loadBalancerService.metadata.namespace || 'default',
				})
        return apiServiceInfo.status.loadBalancer.ingress[0].ip;
    }
}

Consuming the resource

You can consume cdk resource in any workflow/resource.

src/orbits/my-workflow.ts

export class MyWorkflow extends Workflow{
    
    async define(){
        //...
        await this.do("deployMyChart", new MyChartResource().setArgument({
            stackName: "my-chart",
            stackProps: {
                //other props that will be passed to the stack constructors.
                xyz: "xyz",
            }
        }))
    }
}

Resource lifecycle

Update step

The update step deploys the CDK8S stack, using argument.stackProps as input to the StackConstructor.

info

For advanced scenarios (e.g. when needing secrets or dynamic inputs), you can override the init method.

secretValue = ""
async init(){
    this.secretValue = await this.getSecret(this.argument.secretId)
}

This lets you fetch secrets at runtime and ensures they are never stored by Orbits.

The update step processus is :

• synth the stack and deploy it through kubectl apply
• wait for the success of the deployment
• if the deployment is a success, prune old resources
• if the deployment is a failure, rollback to previous state and prune new resources

Cycle step (drift detection)

By default, there is no cycle step defined. However, the cycle hook can be used to do drift detection. In this case, just define a cycle hook and choose what to do inside.

defineCycle(){
    const currentState = await this.do("getCurrentState", ()=>{
        //some call with kube sdk
    })
    if(currentState !== this.argument.stackProps.someParams){
        //choose to redeploy
        await this.do("redeploy", this.clone().setCommand("Update"))
    }
}

By default, the cycle is run every 10 minutes. You can override this parameters overiding defaultResourceSettings.

Uninstall step

The uninstall step removes the CDK8S stack from the kube environment.

Resource output

You can retrieve Kube outputs from the deployed chart using getResourceOutput() method.

        //shortcut to get cloudformation output of the stacks
        const myOutput = await this.do("getMyChartOutput", ()=>{
            return myChartResource.getResourceOutput();
        })
        //output are also available after a deployments
        const myChartOutput = await this.do("deployMyChart", myChartResource);

The type of myChartOutput will be MyChart['IOutput'].

Kube credentials

By default, the stack will be deployed using the local kubeconfig of your environment. However, you can explicitly define how the kubeconfig is selected.

** Example: Using a specific kubeconfig file ** You can specify the way kubeConfig is chosen .

new MyChartResource().setArgument({
    kubeConfig: {
      from : {
        file : '/tmp/my-file', //path to the file
        cluster: boolean
      }
    }
})

** Advanced Use Cases **

In more complex scenarios, you might need to download the kubeconfig dynamically before deploying. You may also want to standardize how kube credentials are handled across all your actions, instead of specifying kubeConfig every time you instantiate a chart resource. To do this, you can override the asynchronous setKubeApi method:

export class MyChartResource extends Cdk8sResource {

  override async setKubeApi() {
    // Download the kubeconfig file, e.g., from your cloud provider
    await getConfigFile(this.argument.clusterName);

    this.kubeApi = new KubeApi({
      from: {
        file: '/path/to/the/downloaded/config'
      }
    });
  }
}