add support for developing in-cluster with Skaffold (#27)

README.md

@@ -161,6 +161,19 @@ docker run -it --rm \
   go build ./cmd/mc-router
 ```
 
+## Skaffold
+
+For "in-cluster development" it's convenient to use https://skaffold.dev. Any changes to Go source code
+will trigger a go build, new container image pushed to registry with a new tag, and refresh in Kubernetes
+with the image tag used in the deployment transparently updated to the new tag and thus new pod created pulling new images:
+
+    skaffold dev
+
+When using Google Cloud (GCP), first create a _Docker Artifact Registry_,
+then add the _Artifact Registry Reader_ Role to the _Compute Engine default service account_ of your GKE clusterService Account_ (to avoid error like "container mc-router is waiting to start: ...-docker.pkg.dev/... can't be pulled"),
+then use e.g. `gcloud auth configure-docker europe-docker.pkg.dev` or equivalent one time (to create a `~/.docker/config.json`),
+and then use e.g. `--default-repo=europe-docker.pkg.dev/YOUR-PROJECT/YOUR-ARTIFACT-REGISTRY` option for `skaffold dev`.
+
 ## Performing snapshot release with Docker
 
 ```bash

docs/k8s-deployment.yaml

@@ -0,0 +1,35 @@
+# used by ../skaffold.yaml
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  labels:
+    run: mc-router
+  name: mc-router
+spec:
+  selector:
+    matchLabels:
+      run: mc-router
+  strategy:
+    type: Recreate
+  template:
+    metadata:
+      labels:
+        run: mc-router
+    spec:
+      serviceAccountName: mc-router
+      containers:
+      - image: itzg/mc-router:latest
+        name: mc-router
+        args: ["--api-binding", ":8080", "--in-kube-cluster"]
+        ports:
+        - name: proxy
+          containerPort: 25565
+        - name: web
+          containerPort: 8080
+        resources:
+          requests:
+            memory: 50Mi
+            cpu: "100m"
+          limits:
+            memory: 100Mi
+            cpu: "250m"

skaffold.yaml

@@ -0,0 +1,14 @@
+apiVersion: skaffold/v2beta26
+kind: Config
+metadata:
+  name: mc-router
+build:
+  artifacts:
+  - image: itzg/mc-router
+    # https://skaffold.dev/docs/pipeline-stages/builders/ko/
+    ko:
+      main: ./cmd/mc-router/
+deploy:
+  kubectl:
+    manifests:
+    - docs/k8s-deployment.yaml