docs(topics): add key-value provider tutorial

Signed-off-by: Vaughn Dice <[email protected]>

content/en/docs/topics/using-a-key-value-store.md

@@ -0,0 +1,158 @@
+---
+title: Using a key value store
+description: Connect your Spin App to a key value store
+date: 2024-07-29
+categories: [Spin Operator]
+tags: [Tutorials]
+weight: 14
+---
+
+Spin applications can utilize a [standardized API for persisting data in a key value store](https://developer.fermyon.com/spin/v2/kv-store-api-guide). The default key value store in Spin is an SQLite database, which is great for quickly utilizing non-relational local storage without any infrastructure set-up. However, this solution may not be preferable for an app running in the context of SpinKube, where apps are often scaled beyond just one replica.
+
+Thankfully, Spin supports configuring an application with an [external key value provider](https://developer.fermyon.com/spin/v2/dynamic-configuration#key-value-store-runtime-configuration). External providers include [Redis](https://redis.io/) or [Valkey](https://valkey.io/) and [Azure Cosmos DB](https://azure.microsoft.com/en-us/products/cosmos-db).
+
+## Prerequisites
+
+To follow along with this tutorial, you'll need:
+
+- A Kubernetes cluster running SpinKube. See the [Installation]({{< relref "install" >}}) guides for more information.
+- The [kubectl CLI](https://kubernetes.io/docs/tasks/tools/#kubectl)
+- The [spin CLI](https://developer.fermyon.com/spin/v2/install )
+
+## Build and publish the Spin application
+
+For this tutorial, we'll use a [Spin key/value application](https://github.com/fermyon/spin-go-sdk/tree/main/examples/key-value) written with the Go SDK. The application serves a CRUD (Create, Read, Update, Delete) API for managing key/value pairs.
+
+First, clone the repository locally and navigate to the `examples/key-value` directory:
+
+```bash
+git clone [email protected]:fermyon/spin-go-sdk.git
+cd examples/key-value
+```
+
+Now, build and push the application to a registry you have access to. Here we'll use [ttl.sh](https://ttl.sh):
+
+```bash
+export IMAGE_NAME=ttl.sh/$(uuidgen):1h
+spin build
+spin registry push ${IMAGE_NAME}
+```
+
+## Configure an external key value provider
+
+Since we have access to a Kubernetes cluster already running SpinKube, we'll choose [Valkey](https://valkey.io/) for our key value provider and install this provider via Bitnami's [Valkey Helm chart](https://github.com/bitnami/charts/tree/main/bitnami/valkey). Valkey is swappable for Redis in Spin, though note we do need to supply a URL using the `redis://` protocol rather than `valkey://`.
+
+```bash
+helm install valkey --namespace valkey --create-namespace oci://registry-1.docker.io/bitnamicharts/valkey
+```
+
+As mentioned in the notes shown after successful installation, be sure to capture the valkey password for use later:
+
+```bash
+export VALKEY_PASSWORD=$(kubectl get secret --namespace valkey valkey -o jsonpath="{.data.valkey-password}" | base64 -d)
+```
+
+## Create a Kubernetes Secret for the Valkey URL
+
+The runtime configuration will require the Valkey URL so that it can connect to this provider. As this URL contains the sensitive password string, we will create it as a Secret resource in Kubernetes:
+
+```bash
+kubectl create secret generic kv-secret --from-literal=valkey-url="redis://:${VALKEY_PASSWORD}@valkey-master.valkey.svc.cluster.local:6379"
+```
+
+## Prepare the SpinApp manifest
+
+You're now ready to assemble the SpinApp custom resource manifest for this application.
+
+- All of the key value config is set under `spec.runtimeConfig.keyValueStores`. See the [keyValueStores reference guide]({{< ref "docs/reference/spin-app#spinappspecruntimeconfigkeyvaluestoresindex" >}}) for more details.
+- Here we configure the `default` store to use the `redis` provider type and under `options` supply the Valkey URL (via its Kubernetes secret)
+
+Plug the `$IMAGE_NAME` and `$DB_URL` values into the manifest below and save as `spinapp.yaml`:
+
+```yaml
+apiVersion: core.spinoperator.dev/v1alpha1
+kind: SpinApp
+metadata:
+  name: kv-app
+spec:
+  image: "$IMAGE_NAME"
+  replicas: 1
+  executor: containerd-shim-spin
+  runtimeConfig:
+    keyValueStores:
+      - name: "default"
+        type: "redis"
+        options:
+          - name: "url"
+            valueFrom:
+              secretKeyRef:
+                name: "kv-secret"
+                key: "valkey-url"
+```
+
+## Create the SpinApp
+
+Apply the resource manifest to your Kubernetes cluster:
+
+```bash
+kubectl apply -f spinapp.yaml
+```
+
+The Spin Operator will handle the creation of the underlying Kubernetes resources on your behalf.
+
+## Test the application
+
+Now you are ready to test the application and verify connectivity and key value storage to the configured provider.
+
+Configure port forwarding from your local machine to the corresponding Kubernetes `Service`:
+
+```bash
+kubectl port-forward services/kv-app 8080:80
+
+Forwarding from 127.0.0.1:8080 -> 80
+Forwarding from [::1]:8080 -> 80
+```
+
+When port forwarding is established, you can send HTTP requests to the application from within an additional terminal session. Here are a few examples to get you started.
+
+Create a `test` key with value `ok!`:
+
+```bash
+$ curl -i -X POST -d "ok!" localhost:8080/test
+HTTP/1.1 200 OK
+content-length: 0
+date: Mon, 29 Jul 2024 19:58:14 GMT
+```
+
+Get the value for the `test` key:
+
+```bash
+$ curl -i -X GET localhost:8080/test
+HTTP/1.1 200 OK
+content-length: 3
+date: Mon, 29 Jul 2024 19:58:39 GMT
+
+ok!
+```
+
+Delete the value for the `test` key:
+
+```bash
+$ curl -i -X DELETE localhost:8080/test
+HTTP/1.1 200 OK
+content-length: 0
+date: Mon, 29 Jul 2024 19:59:18 GMT
+```
+
+Attempt to get the value for the `test` key:
+
+```bash
+$ curl -i -X GET localhost:8080/test
+HTTP/1.1 500 Internal Server Error
+content-type: text/plain; charset=utf-8
+x-content-type-options: nosniff
+content-length: 12
+date: Mon, 29 Jul 2024 19:59:44 GMT
+
+no such key
+```