# Kubernetes

This example illustrates how to use `dagger` to build, push and deploy Docker
images to Kubernetes.

## Prerequisites

### Setup a local Kubernetes cluster

While dagger supports GKE and EKS, for the purpose of this example, we'll be
using [kind](https://kind.sigs.k8s.io/) to install a local Kubernetes cluster
in addition to a local container registry, no cloud account required.

1\. Install kind

Follow [these instructions](https://kind.sigs.k8s.io/docs/user/quick-start) to
install kind.

Alternatively, on macOS using [homebrew](https://brew.sh/):

```shell
brew install kind
```

2\. Start a local registry

```shell
docker run -d -p 5000:5000 --name registry registry:2
```

3\. Create a cluster with the local registry enabled in containerd

```bash
cat <<EOF | kind create cluster --config=-
kind: Cluster
apiVersion: kind.x-k8s.io/v1alpha4
containerdConfigPatches:
- |-
  [plugins."io.containerd.grpc.v1.cri".registry.mirrors."localhost:5000"]
    endpoint = ["http://registry:5000"]
EOF
```

4\. Connect the registry to the cluster network

```shell
docker network connect kind registry
```

## Initialize a Dagger Workspace and Environment

```shell
mkdir dagger-kubernetes && cd dagger-kubernetes
dagger init
dagger new default
```

## Create a basic plan

<!-- `.dagger/env/default/plan`

- `manifest.cue`:
- `deploy.cue`:

[Stateless Application](https://kubernetes.io/docs/tasks/run-application/run-stateless-application-deployment/) -->

Create a file named `.dagger/env/default/plan/manifest.cue` and add the
following configuration to it.

```cue title=".dagger/env/default/plan/manifest.cue"
package main

// inlined kubernetes manifest as a string
manifest: """
  apiVersion: apps/v1
  kind: Deployment
  metadata:
    name: nginx
    labels:
      app: nginx
  spec:
    replicas: 1
    selector:
      matchLabels:
        app: nginx
    template:
      metadata:
        labels:
          app: nginx
      spec:
        containers:
          - name: nginx
            image: nginx:1.14.2
            ports:
              - containerPort: 80
  """
```

This will define a `manifest` variable containing the inlined Kubernetes YAML
used to create a _nginx_ deployment.

Next, create `.dagger/env/default/plan/main.cue`.

```cue title=".dagger/env/default/plan/main.cue"
package main

import (
  "dagger.io/kubernetes"
)

// input: ~/.kube/config file used for deployment
// set with `dagger input text kubeconfig -f ~/.kube/config`
kubeconfig: string @dagger(input)

// deploy uses the `dagger.io/kubernetes` package to apply a manifest to a
// Kubernetes cluster.
deploy: kubernetes.#Apply & {
  // reference the `kubeconfig` input above
  "kubeconfig": kubeconfig

  // reference to the manifest defined in `manifest.cue`
  "manifest": manifest
}
```

This defines:

- `kubeconfig` a _string_ **input**: kubernetes configuration (`~/.kube/config`)
  used for `kubectl`
- `deploy`: Deployment step using the package `dagger.io/kubernetes`. It takes
  the `manifest` defined earlier and deploys it to the Kubernetes cluster specified in `kubeconfig`.

### Configure the environment

Before we can bring up the deployment, we need to provide the `kubeconfig` input
declared in the configuration. Otherwise, dagger will complain about a missing input:

```shell
$ dagger up
6:53PM ERR system | required input is missing    input=kubeconfig
```

You can inspect the list of inputs (both required and optional) using `dagger input list`:

```shell
$ dagger input list
Input             Type              Description
kubeconfig        string            ~/.kube/config file used for deployment
deploy.namespace  string            Kubernetes Namespace to deploy to
```

Let's provide the missing input:

```shell
# we'll use the ~/.kube/config created by `kind`
dagger input text kubeconfig -f ~/.kube/config
```

### Deploying

Now is time to deploy to kubernetes.

```shell
$ dagger up
deploy | computing
deploy | #26 0.700 deployment.apps/nginx created
deploy | completed    duration=900ms
```

Let's verify the deployment worked:

```shell
$ kubectl get deployments
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           1m
```

## CUE Kubernetes manifests

In this section we will convert the inlined YAML manifest to CUE to take advantage of the language features.

For a more advanced example, see the
[official CUE Kubernetes tutorial](https://github.com/cuelang/cue/blob/v0.4.0/doc/tutorial/kubernetes/README.md)

First, let's replace `manifest.cue` with the following configuration. This is a
straightforward one-to-one conversion from YAML to CUE, only the syntax has changed.

```cue title=".dagger/env/default/plan/manifest.cue"
package main

import (
  "encoding/yaml"
)

nginx: {
  apiVersion: "apps/v1"
  kind:       "Deployment"
  metadata: {
    "name": "nginx"
    labels: app: "nginx"
  }
  spec: {
    replicas: 1
    selector: matchLabels: app: "nginx"
    template: {
      metadata: labels: app: "nginx"
      spec: containers: [{
        "name":  "nginx"
        "image": image
        ports: [{
          containerPort: port
        }]
      }]
    }
  }
}

manifest: yaml.Marshal(nginx)
```

We're using the built-in `yaml.Marshal` function to convert CUE back to YAML so
Kubernetes still receives the same manifest.

You can inspect the configuration using `dagger query` to verify it produces the
same manifest:

```shell
$ dagger query manifest -f text
apiVersion: apps/v1
kind: Deployment
...
```

Now that the manifest is defined in CUE, we can take advantage of the language
to remove a lot of boilerplate and repetition.

Let's define a re-usable `#Deployment` definition in `.dagger/env/default/plan/deployment.cue"`:

```cue title=".dagger/env/default/plan/deployment.cue"
package main

// Deployment template containing all the common boilerplate shared by
// deployments of this application.
#Deployment: {
  // name of the deployment. This will be used to automatically label resouces
  // and generate selectors.
  name: string

  // container image
  image: string

  // 80 is the default port
  port: *80 | int

  // 1 is the default, but we allow any number
  replicas: *1 | int

  // Deployment manifest. Uses the name, image, port and replicas above to
  // generate the resource manifest.
  manifest: {
    apiVersion: "apps/v1"
    kind:       "Deployment"
    metadata: {
      "name": name
      labels: app: name
    }
    spec: {
      "replicas": replicas
      selector: matchLabels: app: name
      template: {
        metadata: labels: app: name
        spec: containers: [{
          "name":  name
          "image": image
          ports: [{
            containerPort: port
          }]
        }]
      }
    }
  }
}
```

`manifest.cue` can be rewritten as follows:

```cue title=".dagger/env/default/plan/manifest.cue"
import (
  "encoding/yaml"
)

nginx: #Deployment & {
  name:  "nginx"
  image: "nginx:1.14.2"
}

manifest: yaml.Marshal(nginx.manifest)
```

Let's make sure it yields the same result:

```shell
$ dagger query deploy.manifest -f text
apiVersion: apps/v1
kind: Deployment
...
```

And we can now deploy it:

```shell
$ dagger up
deploy | computing
deploy | #26 0.700 deployment.apps/nginx unchanged
deploy | completed    duration=900ms
```

## Building, pushing and deploying Docker images

Rather than deploying an existing (`nginx`) image, we're going to build a Docker
image from source, push it to a registry and update the kubernetes configuration.

### Update the plan

The following configuration will:

- Declare a `repository` input as a `dagger.#Artifact`. This will be mapped to
  the source code directory.
- Declare a `registry` input. This is the address used for docker push
- Use `dagger.io/docker` to build and push the image
- Use the registry image reference (`push.ref`) as the image for the deployment.

```cue title=".dagger/env/default/plan/manifest.cue"
package main

import (
  "encoding/yaml"

  "dagger.io/docker"
)

// input: source code repository, must contain a Dockerfile
// set with `dagger input dir repository ./app`
repository: dagger.#Artifact @dagger(input)

// registry to push images to
registry: string @dagger(input)

// docker build the `repository` directory
image: docker.#Build & {
    source: repository
}

// push the `image` to the `registry`
push: docker.#Push & {
  source: image
  ref: registry
}

// use the `#Deployment` template to generate the kubernetes manifest
app: #Deployment & {
  name: "test"

  // use the reference of the image we just pushed
  // this creates a dependency: `app` will only be deployed after the image is
  // built and pushed.
  "image": push.ref
}

manifest: yaml.Marshal(app.manifest)
```

### Connect the Inputs

Next, we'll provide the two new inputs, `repository` and `registry`.

For the purpose of this tutorial we'll be using
[hello-go](https://github.com/aluzzardi/hello-go) as example source code.

```shell
$ git clone https://github.com/aluzzardi/hello-go.git
dagger input dir repository ./hello-go
dagger input text registry "localhost:5000/image"
```

### Bring up the changes

```shell
$ dagger up
repository | computing
repository | completed    duration=0s
image | computing
image | completed    duration=1s
deploy | computing
deploy | #26 0.709 deployment.apps/hello created
deploy | completed    duration=900ms
```

Let's verify the deployment worked:

```shell
$ kubectl get deployments
NAME    READY   UP-TO-DATE   AVAILABLE   AGE
nginx   1/1     1            1           1m
hello   1/1     1            1           1m
```

## Next Steps

Deploy on a hosted Kubernetes cluster:

- [GKE](https://github.com/dagger/dagger/tree/main/stdlib/gcp/gke)
- [EKS](https://github.com/dagger/dagger/tree/main/stdlib/aws/eks)

Authenticate to a remote registry:

- [ECR](https://github.com/dagger/dagger/tree/main/stdlib/aws/ecr)
- [GCR](https://github.com/dagger/dagger/tree/main/stdlib/gcp/gcr)

Integrate kubernetes tools with Dagger:

- [Helm](https://github.com/dagger/dagger/tree/main/stdlib/kubernetes/helm)
- [Kustomize](https://github.com/dagger/dagger/tree/main/stdlib/kubernetes/kustomize)