# cdk8s+ (cdk8s-plus)
> 
> This library is in very early stages of development, as such, and in correspondence with a `0.x` semantic major version line, its `API` is
likely to rapidly change in breaking ways. It is therefore not recommended to use library for production workloads.
**cdk8s+** is a software development framework that provides high level abstractions for authoring Kubernetes applications.
Built on top of the auto generated building blocks provided by [cdk8s](../cdk8s), this library includes a hand crafted *construct*
for each native kubernetes object, exposing richer API's with reduced complexity.
## Kubernetes Spec
**cdk8s+** is currently built on top of version [1.17.0](https://github.com/instrumenta/kubernetes-json-schema/tree/master/v1.17.0) of the kubernetes API specifications.
If you are deploying manifests produced by `cdk8s+` onto clusters of a lower version, you might encounter some unsupported spec properties or invalid manifests.
> See [Supporting various k8s API specs](https://github.com/awslabs/cdk8s/issues/299) for more details and progress on this issue.
## Letter Of Intent
We strive to develop this library with full transparency and as much community feedback and contributions as possible.
To that end, we publish this development version. The lack of features/capabilities is intentional, we look forward to build and expand this framework with the help of the community.
> If you are interested in contributing, see [Contribution Guide](./CONTRIBUTING.md).
## At a glance
```typescript
import * as kplus from 'cdk8s-plus';
import * as cdk8s from 'cdk8s';
import * as path from 'path';
// our cdk app
const app = new cdk8s.App();
// our kuberentes chart
const chart = new cdk8s.Chart(app, 'Chart');
// lets create a volume that contains our app.
// we use a trick with a config map!
const appData = new kplus.ConfigMap(chart, 'AppData');
appData.addDirectory(path.join(__dirname, 'app'));
const appVolume = kplus.Volume.fromConfigMap(appData);
// now we create a container that runs our app
const appPath = '/var/lib/app';
const port = 80;
const container = new kplus.Container({
image: 'node:14.4.0-alpine3.12',
command: ['node', 'index.js', `${port}`],
port: port,
workingDir: appPath,
})
// make the app accessible to the container
container.mount(appPath, appVolume);
// now lets create a deployment to run a few instances of this container
const deployment = new kplus.Deployment(chart, 'Deployment', {
replicas: 3,
containers: [ container ]
});
// finally, we expose the deployment as a load balancer service and make it run
deployment.expose(8080, {serviceType: kplus.ServiceType.LOAD_BALANCER})
// we are done, synth
app.synth();
```
```yaml
apiVersion: v1
data:
index.js: |-
var http = require('http');
var port = process.argv[2];
//create a server object:
http.createServer(function (req, res) {
res.write('Hello World!'); //write a response to the client
res.end(); //end the response
}).listen(port); //the server object listens on port 80
kind: ConfigMap
metadata:
annotations: {}
labels: {}
name: chart-appdata-configmap-da4c63ab
---
apiVersion: apps/v1
kind: Deployment
metadata:
annotations: {}
labels: {}
name: chart-deployment-pod-d4285cc9
spec:
replicas: 3
selector:
matchLabels:
cdk8s.deployment: ChartDeploymentCFC2E30C
template:
metadata:
annotations: {}
labels:
cdk8s.deployment: ChartDeploymentCFC2E30C
spec:
containers:
- command:
- node
- index.js
- "80"
env: []
image: node:14.4.0-alpine3.12
name: main
ports:
- containerPort: 80
volumeMounts:
- mountPath: /var/lib/app
name: configmap-chart-appdata-configmap-da4c63ab
workingDir: /var/lib/app
volumes:
- configMap:
name: chart-appdata-configmap-da4c63ab
name: configmap-chart-appdata-configmap-da4c63ab
---
apiVersion: v1
kind: Service
metadata:
annotations: {}
labels: {}
name: chart-deployment-service-pod-42f50c26
spec:
externalIPs: []
ports:
- port: 8080
targetPort: 80
selector:
cdk8s.deployment: ChartDeploymentCFC2E30C
type: LoadBalancer
```
## Installation and Usage
We currently support both Python and TypeScript/JavaScript. More languages are coming soon.
> We would love to hear which languages you want to see next: [Languages Support](https://github.com/awslabs/cdk8s/issues/134)
### TypeScript/JavaScript
`❯ npm install cdk8s-plus cdk8s`
```typescript
import * as kplus from 'cdk8s-plus';
import * as cdk8s from 'cdk8s';
const app = new cdk8s.App();
const chart = new cdk8s.Chart(app, 'Chart');
new kplus.Deployment(chart, 'Deployment', {
replicas: 3,
containers: [new kplus.Container({
image: 'ubuntu',
})],
});
```
### Python
`❯ pip install cdk8s-plus cdk8s`
```python
import cdk8s_plus as kplus
import cdk8s
app = cdk8s.App()
chart = cdk8s.Chart(app, 'Chart')
kplus.Deployment(chart, 'Deployment',
replicas=1,
containers=[kplus.Container(image='ubuntu')]
)
```
## In Depth
Following are excerpts for the usage of every *construct* provided by this library. It details the commonly used patterns and configuration properties.
In general, every such construct can be configured using two mechanisms:
- Spec Constructor Properties
- Post Instantiation Spec Mutations
The documentation presented here focuses on post instantiation mutations, however, every such mutation can also be pre-configured
using constructor properties for the corresponding spec. A complete API reference can be found in [here](./API.md).
### `Container`
Define containers that run in a pod using the `Container` class.
> API Reference: [Container](./API.md#cdk8s-plus-container)
#### Environment variables
Environment variables can be added to containers using various sources, via semantically explicit API's:
```typescript
import * as kplus from 'cdk8s-plus'
const container = new kplus.Container({
image: 'my-app'
})
// explicitly use a value.
container.addEnv('endpoint', kplus.EnvValue.fromValue('value'));
// use a specific key from a config map.
const backendsConfig = kplus.ConfigMap.fromConfigMapName('backends');
container.addEnv('endpoint', kplus.EnvValue.fromConfigMap(backendsConfig, 'endpoint'));
// use a specific key from a secret.
const credentials = kplus.Secret.fromSecretName('credentials');
container.addEnv('password', kplus.EnvValue.fromSecret(credentials, 'password'));
```
#### Volume Mounts
A very common capability is to mount a volume with some data onto a container. Using pure kubernetes API, this would require writing something like:
```yaml
kind: Pod
apiVersion: v1
spec:
containers:
- name: main
volumeMounts:
- mountPath: /path/to/mount
name: 'config-volume'
volumes:
- name: 'config-volume'
configMap:
name: 'config'
```
Notice the apparent redundancy of having to specify the volume name twice. Also, if you happen to need the same mount in other pods,
you would need to duplicate this configuration. This can get complex and cluttered very fast.
In contrast, here is how to do this with `cdk8s+`:
```typescript
import * as kplus from 'cdk8s-plus';
const config = kplus.ConfigMap.fromConfigMapName('config');
const volume = kplus.Volume.fromConfigMap(config);
const container = new kplus.Container({
image: 'my-app'
})
// Cool alert: every pod that will later be configured with this container,
// will automatically have access to this volume, so you don't need to explicitly add it to the pod spec!.
container.mount('/path/to/mount', volume);
```
## Probes
A [Probe] is a diagnostic performed periodically by the kubelet on a Container. To
perform a diagnostic, the kubelet calls a Handler implemented by the container.
[Probe]: https://kubernetes.io/docs/reference/generated/kubernetes-api/v1.19/#probe-v1-core
A `Probe` instance can be created through one of the `fromXxx` static methods:
- `Probe.fromHttpGet()`
- `Probe.fromCommand()`
Readiness probes can be configured at the container-level through the `readiness` option:
```ts
new kplus.Container({
// ...
readiness: kplus.Probe.fromHttpGet('/ping')
});
```
See the API reference for details.
### `Volume`
Volume represents a named volume in a pod that may be accessed by any container in the pod.
> API Reference: [Volume](./API.md#cdk8s-plus-volume)
#### Create from a ConfigMap
A very useful operation is to create a volume from a `ConfigMap`. Kubernetes will translate every key in the config map to a file,
who's content is the value of the key.
```typescript
import * as kplus from 'cdk8s-plus';
const configMap = kplus.ConfigMap.fromConfigMapName('redis-config');
const configVolume = kplus.Volume.fromConfigMap(configMap);
```
#### Create from an EmptyDir
The easiest way to allocate some persistent storage to your container is to create a volume from an empty directory.
This volume, as the name suggests, is initially empty, and can be written to by containers who mount it.
The data in the volume is preserved throughout the lifecycle of the pod, but is deleted forever as soon as the pod itself is removed.
```typescript
import * as kplus from 'cdk8s-plus';
const data = kplus.Volume.fromEmptyDir(configMap);
const redis = new kplus.Container({
image: 'redis'
})
// mount to the redis container.
redis.mount('/var/lib/redis', data);
```
### `Job`
Jobs are a very useful concept in kubernetes deployments.
They can be used for add-hoc provisioning tasks, as well as long running processing jobs.
> API Reference: [Job](./API.md#cdk8s-plus-job)
In configuration, they don't differ much from regular pods, but offer some additional properties.
#### Delete a Job after its finished
You can configure a TTL for the job after it finished its execution successfully.
```typescript
import * as k from 'cdk8s';
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
// let's define a job spec, and set a 1 second TTL.
const load = new kplus.Job(chart, 'LoadData', {
ttlAfterFinished: kplus.Duration.seconds(1)
});
// now add a container to all the pods created by this job
job.addContainer(new kplus.Container({
image: 'loader'
}));
```
### `Service`
Use services when you want to expose a set of pods using a stable network identity. They can also be used for externalizing
endpoints to clients outside of the kubernetes cluster.
> API Reference: [Service](./API.md#cdk8s-plus-service)
#### Selectors
Services must be configured with selectors that tell it which pods should it serve.
The most common selector method is using labels.
```typescript
import * as k from 'cdk8s';
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const frontends = new kplus.Service(chart, 'FrontEnds');
// this will cause the service to select all pods with the 'run: frontend' label.
frontends.selectByLabel('run', 'frontend')
```
#### Ports
Ports that the service will listen and redirect to can be configured like so:
```typescript
import * as k from 'cdk8s';
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const frontends = new kplus.Service(chart, 'FrontEnds');
// make the service bind to port 9000 and redirect to port 80 on the associated containers.
frontends.serve({port: 9000, targetPort: 80)
```
### `Deployment`
Create a deployment to govern the lifecycle and orchestration of a set of identical pods.
> API Reference: [Deployment](./API.md#cdk8s-plus-deployment)
#### Automatic pod selection
When you specify pods in a deployment, you normally have to configure the appropriate labels and selectors to
make the deployment control the relevant pods. This construct does this automatically.
```typescript
import * as k from 'cdk8s';
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
new kplus.Deployment(chart, 'FrontEnds', {
containers: [ new kplus.Container({ image: 'node' }) ],
});
```
Note the resulting manifest contains a special `cdk8s.deployment` label that is applied to the pods, and is used as
the selector for the deployment.
```yaml
apiVersion: apps/v1
kind: Deployment
metadata:
annotations: {}
labels: {}
name: chart-frontends-pod-a48e7f2e
spec:
replicas: 1
selector:
matchLabels:
cdk8s.deployment: ChartFrontEndsDD8A97CE
template:
metadata:
annotations: {}
labels:
cdk8s.deployment: ChartFrontEndsDD8A97CE
```
#### Exposing via a service
Following up on pod selection, you can also easily create a service that will select the pods relevant to the deployment.
```typescript
// store the deployment to created in a constant
const frontends = new kplus.Deployment(chart, 'FrontEnds');
// create a ClusterIP service that listens on port 9000 and redirects to port 9000 on the containers.
frontends.expose(9000)
```
Notice the resulting manifest, will have the same `cdk8s.deployment` magic label as the selector.
This will cause the service to attach to the pods that were configured as part of the said deployment.
```yaml
apiVersion: v1
kind: Service
metadata:
annotations: {}
labels: {}
name: chart-frontends-service-pod-1f70150b
spec:
externalIPs: []
ports:
- port: 9000
selector:
cdk8s.deployment: ChartFrontEndsDD8A97CE
type: ClusterIP
```
### `ConfigMap`
ConfigMap are used to store configuration data. They provide a dictionary based data structure that can be consumed in
various shapes and forms.
> API Reference: [ConfigMap](./API.md#cdk8s-plus-configmap)
#### Use an existing `ConfigMap`
You can reference to an existing `ConfigMap` like so. Note that this does not create a new object,
and will therefore not be included in the resulting manifest.
```typescript
import * as kplus from 'cdk8s-plus';
const config: kplus.IConfigMap = kplus.ConfigMap.fromConfigMapName('config');
// the 'config' constant can later be used by API's that require an IConfigMap.
// for example when creating a volume.
const volume = kplus.Volume.fromConfigMap(config);
```
#### Adding data
You can create config maps and add some data to them like so:
```typescript
import * as kplus from 'cdk8s-plus';
import * as k from 'cdk8s';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const config = new new kplus.ConfigMap(chart, 'Config');
config.addData('url', 'https://my-endpoint:8080');
```
#### Creating a volume from a directory
Here is a nifty little trick you can use to create a volume that contains a directory on the client machine (machine that runs `cdk8s synth`):
```typescript
import * as kplus from 'cdk8s-plus';
import * as k from 'cdk8s';
import * as path from 'path';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const appMap = new new kplus.ConfigMap(chart, 'Config');
// add the files in the directory to the config map.
// this will create a key for each file.
// note that only top level files will be included, sub-directories are not yet supported.
appMap.addDirectory(path.join(__dirname, 'app'));
const appVolume = kplus.Volume.fromConfigMap(appMap);
// for here, just mount the volume to a container, and run your app!
const mountPath = '/var/app';
const container = new kplus.Container({
image: 'node',
command: [ 'node', 'app.js' ],
workingDir: mountPath,
})
container.mount(mountPath, appVolume);
```
### `Pod`
A pod is essentially a collection of containers. It is the most fundamental computation unit that can be provisioned.
> API Reference: [Pod](./API.md#cdk8s-plus-pod)
#### Adding Containers/Volumes
Containers and volumes can be added to pod definition like so:
```typescript
import * as kplus from 'cdk8s-plus';
const container = new kplus.Container({
image: 'node',
})
const storage = kplus.Volume.fromEmptyDir('storage');
container.mount('/data', storage);
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const pod = new new kplus.Pod(chart, 'Pod');
// this will automatically add the volume as well.
pod.addContainer(container);
// but if you want to explicitly add it, simply use:
pod.addVolume(storage);
```
#### Applying a restart policy
```typescript
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const pod = new new kplus.Pod(chart, 'Pod', {
restartPolicy: kplus.RestartPolicy.NEVER,
});
```
#### Assigning a ServiceAccount
```typescript
import * as kplus from 'cdk8s-plus';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const pod = new new kplus.Pod(chart, 'Pod', {
serviceAccount: kplus.ServiceAccount.fromServiceAccountName('aws'),
});
```
### `Secret`
Secrets are used to store confidential information. Never store such information on the definition of the pod itself.
> API Reference: [Secret](./API.md#cdk8s-plus-secret)
#### Use an existing `Secret`
To reference a secret created outside of your deployment definition, use the following. Note that this does not create a new object,
and will therefore not be included in the resulting manifest.
```typescript
import * as kplus from 'cdk8s-plus';
const secret = kplus.Secret.fromSecretName('aws-creds');
```
#### Adding data
To create a new secret with some data, use:
```typescript
import * as kplus from 'cdk8s-plus';
import * as k from 'cdk8s';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const secret = new kplus.Secret(chart, 'Secret');
secret.addStringData('password', 'some-encrypted-data');
```
### `ServiceAccount`
Use service accounts to provide an identity for pods.
> API Reference: [ServiceAccount](./API.md#cdk8s-plus-serviceaccount)
#### Use an existing `ServiceAccount`
To reference a service account created outside of your deployment definition, use the following. Note that this does not create a new object,
and will therefore not be included in the resulting manifest.
```typescript
import * as kplus from 'cdk8s-plus';
const serviceAccount = kplus.ServiceAccount.fromServiceAccountName('aws-service');
```
#### Allowing access to secrets
To create a new service account, and give it access to some secrets, use the following:
```typescript
import * as kplus from 'cdk8s-plus';
import * as k from 'cdk8s';
const app = new k.App();
const chart = new k.Chart(app, 'Chart');
const awsCreds = kplus.Secret.fromSecretName('aws-creds');
const awsService = new kplus.ServiceAccount(chart, 'AWS');
// give access to the aws creds secret.
awsService.addSecret(awsCreds);
```
### `Ingress`
[Ingress] manages external access to services in a cluster, typically through
HTTP. Ingress may provide load balancing, SSL termination and name-based virtual
hosting.
You must have an [Ingress controller] to satisfy an Ingress. Only creating an
Ingress resource has no effect.
> API Reference: [Ingress](./API.md#cdk8s-plus-ingress)
[Ingress]: https://kubernetes.io/docs/concepts/services-networking/ingress/
[Ingress controller]: https://kubernetes.io/docs/concepts/services-networking/ingress-controllers
The following example will route HTTP requests sent to the `/hello` url prefix
to a service associated with a deployment of the
[hashicorp/http-echo](https://github.com/hashicorp/http-echo) image.
```ts
const helloDeployment = new kplus.Deployment(this, text, {
containers: [
new kplus.Container({
image: 'hashicorp/http-echo',
args: [ '-text', 'hello ingress' ]
})
]
});
const helloService = helloDeployment.expose(5678);
const ingress = new Ingress(this, 'ingress');
ingress.addRule('/hello', kplus.IngressBackend.fromService(helloService));
```
You can use `addHostRule(host, path, backend)` to define a route that will only
apply to requests with this `Host` header. This can be used to implement virtual
hosts.
The `addDefaultBackend(backend)` and `addHostDefaultBackend(host, backend)`
methods can be used to define backends that will accept all requests that do not
match any other rules.
The TCP port used to route requests to services will be determined based on
which ports are exposed by the service (e.g. through `serve()`). If the service
exposes multiple ports, then a port must be specified via
`IngressBackend.fromService(service, { port }`.