Deploy the nats-server helm chart on Google Kubernetes Engine (GKE)

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Pulumi · Accepted Answer

To deploy the `nats-server` helm chart on Google Kubernetes Engine (GKE), you will need to perform the following steps:

1. **Set up a GKE cluster**: This is where your `nats-server` workloads will run. You need a Kubernetes cluster on GKE to be able to deploy Helm charts onto it.
2. **Install and configure `helm`**: Helm is a package manager for Kubernetes, which allows you to deploy charts (pre-packaged applications) to your cluster easily.
3. **Deploy the `nats-server` Helm chart**: Once Helm is set up and you have your GKE cluster ready, you can deploy the `nats-server` helm chart to the cluster.

Below you will find a Pulumi TypeScript program that illustrates how to accomplish these steps:

1. Create a new GKE cluster.
2. Deploy the `nats-server` helm chart to the newly created GKE cluster.

Let's go through this process step by step.

```typescript
import * as gcp from "@pulumi/gcp";
import * as k8s from "@pulumi/kubernetes";

// Step 1: Create the GKE cluster
const cluster = new gcp.container.Cluster("my-cluster", {
    initialNodeCount: 2,
    minMasterVersion: "latest",
    nodeConfig: {
        machineType: "n1-standard-1",
        oauthScopes: [
            "https://www.googleapis.com/auth/compute",
            "https://www.googleapis.com/auth/devstorage.read_only",
            "https://www.googleapis.com/auth/logging.write",
            "https://www.googleapis.com/auth/monitoring"
        ],
    },
});

// Export the Cluster name
export const clusterName = cluster.name;

// Export the Kubeconfig to access the GKE cluster with kubectl
export const kubeconfig = cluster.endpoint.apply(endpoint => JSON.stringify({
    "apiVersion": "v1",
    "clusters": [{
        "cluster": {
            "certificate-authority-data": cluster.masterAuth.clusterCaCertificate,
            "server": `https://${endpoint}`
        },
        "name": "kubernetes"
    }],
    "contexts": [{
        "context": {
            "cluster": "kubernetes",
            "user": "client",
        },
        "name": "client-context"
    }],
    "current-context": "client-context",
    "kind": "Config",
    "preferences": {},
    "users": [{
        "name": "client",
        "user": {
            "client-certificate-data": cluster.masterAuth.clientCertificate,
            "client-key-data": cluster.masterAuth.clientKey,
            "auth-provider": {
                "name": "gcp"
            }
        }
    }]
}));

// Step 2: Deploy the nats-server helm chart
const natsServerChart = new k8s.helm.v3.Chart("nats-server", {
    chart: "nats",
    version: "0.7.x",  // Specify the version of the chart to use
    fetchOpts: {
        repo: "https://nats-io.github.io/k8s/helm/charts/",
    },
}, { provider: new k8s.Provider("k8s-provider", { kubeconfig }) });

// Export the Helm chart name
export const helmChartName = natsServerChart.chart;
```

### How the program works:
1. **Create the GKE cluster**: The `gcp.container.Cluster` resource is used to create a new GKE cluster with:
    - A defined number of nodes (`initialNodeCount`).
    - Specific machine type for each node (`machineType`).
    - Necessary OAuth scopes for the nodes to interact with the Google Cloud services.

**Important Note**: In a production environment, you would also want to configure additional settings such as the network and subnetwork, more robust security settings, etc.

2. **Generate Kubeconfig**: Pulumi provides us with a way to fetch the necessary information to construct a kubeconfig file, which can be used to interact with the newly created GKE cluster using tools like `kubectl`.

3. **Install the NATS Server Helm chart**: We use the `k8s.helm.v3.Chart` resource, which represents a Helm chart in Kubernetes.
   - `chart`: Name of the chart (in this case, "nats").
   - `version`: Which version of the chart to deploy.
   - `repo`: The URL to the chart repository.
   
   This resource is then provided with the kubeconfig we obtained from the cluster creation step.

### Resources Used:
- [gcp.container.Cluster](https://www.pulumi.com/docs/reference/pkg/gcp/container/cluster/) for creating the GKE cluster.
- [k8s.helm.v3.Chart](https://www.pulumi.com/docs/reference/pkg/kubernetes/helm/v3/chart/) for deploying the helm chart.

To run this Pulumi program, you would need to have `pulumi-cli` installed and configured for GCP authentication. Then, you would typically run `pulumi up` to apply the program and create the resources. If you are new to Pulumi and would like to learn more about it, the [Pulumi Get Started](https://www.pulumi.com/docs/get-started/) guide is a great resource.