keepalive

Author: mike-callahan

Dockerfile

@@ -0,0 +1,13 @@
+FROM golang:1.21.12
+
+WORKDIR /usr/src/app
+
+# pre-copy/cache go.mod for pre-downloading dependencies and only redownloading them in subsequent builds if they change
+COPY go.mod ./
+
+COPY . .
+RUN go build -v -o /usr/bin/k8s-keepalive ./...
+
+EXPOSE 5000
+
+CMD ["/usr/bin/k8s-keepalive"]

go.mod

@@ -0,0 +1,3 @@
+module github.com/mike-callahan/k8s-keepalive
+
+go 1.21.12

k8s-keepalive.go

@@ -0,0 +1,40 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"log"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+)
+
+func main() {
+	log.Println("Starting keepalive service...")
+	handler := http.HandlerFunc(HTTPProbe)
+	server := &http.Server{
+		Addr:    ":5000",
+		Handler: handler,
+	}
+
+	go func() {
+		if err := server.ListenAndServe(); !errors.Is(err, http.ErrServerClosed) {
+			log.Fatalf("HTTP server error: %v", err)
+		}
+		log.Println("Stopped serving new connections.")
+	}()
+
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, syscall.SIGINT, syscall.SIGTERM)
+	<-sigChan
+
+	shutdownCtx, shutdownRelease := context.WithTimeout(context.Background(), 10*time.Second)
+	defer shutdownRelease()
+
+	if err := server.Shutdown(shutdownCtx); err != nil {
+		log.Fatalf("HTTP shutdown error: %v", err)
+	}
+	log.Println("Graceful shutdown complete.")
+}

web.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// Check if the status code passed by the user is valid
+func IsValidHTTPStatusCode(code int) bool {
+	return code >= 100 && code <= 599
+}
+
+// Respond to k8s health probes
+// Additional functionality of allowing user to pass arbitrary status codes for testing
+func HTTPProbe(w http.ResponseWriter, r *http.Request) {
+	// Error if the request isn't Get or Post
+	if r.Method != http.MethodGet && r.Method != http.MethodPost {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintln(w, "Only GET and POST requests are allowed")
+		return
+	}
+
+	// Send 200 for /
+	path := strings.TrimPrefix(r.URL.Path, "/")
+	if path == "" || path == "healthz" {
+		// Default response
+		w.WriteHeader(http.StatusOK)
+		fmt.Fprintln(w, "Hello! Pass a status code in the URL path (e.g., /200 or /404)")
+		return
+	}
+
+	statusCode, _ := strconv.Atoi(path)
+	_, err := strconv.Atoi(path)
+
+	// Error if string can't be converted to integer
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintln(w, "That is not a valid status code or integer.")
+		return
+	}
+
+	// Error if integer is out of validity range
+	err = nil
+	if IsValidHTTPStatusCode(statusCode) == false {
+		err = errors.New("That integer is not a valid status code")
+	}
+
+	if err != nil {
+		w.WriteHeader(http.StatusBadRequest)
+		fmt.Fprintln(w, fmt.Errorf("Error processing data: %w", err))
+		return
+	}
+
+	// Write value back to header and body
+	w.WriteHeader(statusCode)
+	fmt.Fprintf(w, "%d", statusCode)
+}

web_test.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestHTTPProbe(t *testing.T) {
+	t.Run("Return default status", func(t *testing.T) {
+		request, _ := http.NewRequest(http.MethodGet, "/", nil)
+		response := httptest.NewRecorder()
+
+		HTTPProbe(response, request)
+
+		got := response.Result().StatusCode
+		want := 200
+
+		if got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+
+	})
+	t.Run("Return status 200", func(t *testing.T) {
+		request, _ := http.NewRequest(http.MethodGet, "/200", nil)
+		response := httptest.NewRecorder()
+
+		HTTPProbe(response, request)
+
+		got := response.Result().StatusCode
+		want := 200
+
+		if got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+
+	})
+
+	t.Run("Return status 404", func(t *testing.T) {
+		request, _ := http.NewRequest(http.MethodGet, "/404", nil)
+		response := httptest.NewRecorder()
+
+		HTTPProbe(response, request)
+
+		got := response.Result().StatusCode
+		want := 404
+
+		if got != want {
+			t.Errorf("got %q, want %q", got, want)
+		}
+
+	})
+
+	t.Run("Return status non-status", func(t *testing.T) {
+		request, _ := http.NewRequest(http.MethodGet, "/asdf", nil)
+		response := httptest.NewRecorder()
+
+		HTTPProbe(response, request)
+
+		got := response.Result().StatusCode
+		want := 400
+
+		if got != want {
+			t.Errorf("got %d, want %d", got, want)
+		}
+
+	})
+
+	t.Run("PATCH method", func(t *testing.T) {
+		request, _ := http.NewRequest(http.MethodPatch, "/asdf", nil)
+		response := httptest.NewRecorder()
+
+		HTTPProbe(response, request)
+
+		got := response.Result().StatusCode
+		want := 400
+
+		if got != want {
+			t.Errorf("got %d, want %d", got, want)
+		}
+
+	})
+}