[deployment] feat: add deployment readiness tutorial.

Author: guangzhengli

deployment/readiness/Dockerfile

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+# Dockerfile
+FROM golang:1.16-buster AS builder
+RUN mkdir /src
+ADD . /src
+WORKDIR /src
+
+RUN go env -w GO111MODULE=auto
+RUN go build -o main .
+
+FROM gcr.io/distroless/base-debian10
+
+WORKDIR /
+
+COPY --from=builder /src/main /main
+EXPOSE 3000
+ENTRYPOINT ["/main"]

deployment/readiness/deployment.yaml

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+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: hellok8s-deployment
+spec:
+  strategy:
+     rollingUpdate:
+      maxSurge: 1
+      maxUnavailable: 1
+  replicas: 3
+  selector:
+    matchLabels:
+      app: hellok8s
+  template:
+    metadata:
+      labels:
+        app: hellok8s
+    spec:
+      containers:
+        - image: guangzhengli/hellok8s:bad
+          name: hellok8s-container
+          readinessProbe:
+            httpGet:
+              path: /healthz
+              port: 3000
+            initialDelaySeconds: 1
+            successThreshold: 5

deployment/readiness/main.go

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+package main
+
+import (
+	"io"
+	"net/http"
+)
+
+func hello(w http.ResponseWriter, r *http.Request) {
+	io.WriteString(w, "[v2] Hello, Kubernetes!")
+}
+
+func main() {
+	http.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+			w.WriteHeader(500)
+	})
+
+	http.HandleFunc("/", hello)
+	http.ListenAndServe(":3000", nil)
+}