新增learn-kubernetes（https://github.com/yyong-brs/learn-kubernetes）相关文件

learn/learn-kubernetes-master/kiamol/ch14/docker-images/image-gallery/main.go

@@ -0,0 +1,78 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"html/template"
+	"io/ioutil"	
+	"math/rand"
+	"net/http"
+	"os"
+	"time"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type Image struct {
+	Url       string `json:"url"`
+	Caption   string `json:"caption"`
+	Copyright string `json:"copyright"`
+}
+
+type AccessLog struct {
+	ClientIP  string `json:"clientIp"`
+}
+
+func main() {
+	tmpl := template.Must(template.ParseFiles("index.html"))
+	imageApiUrl :=  os.Getenv("IMAGE_API_URL")
+	logApiUrl := os.Getenv("ACCESS_API_URL")
+
+	//re-use HTTP client with minimal keep-alive
+	tr := &http.Transport{
+		MaxIdleConns: 1,
+	    IdleConnTimeout: 1 * time.Second,
+	}
+	client := &http.Client{Transport: tr}
+
+	//create Prometheus metrics
+	inFlightGauge := prometheus.NewGauge(prometheus.GaugeOpts{
+		Name: "image_gallery_in_flight_requests",
+		Help: "Image Gallery - in-flight requests",
+	})
+	requestCounter := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "image_gallery_requests_total",
+			Help: "Image Gallery - total requests",
+		},
+		[]string{"code", "method"},
+	)
+
+	prometheus.MustRegister(inFlightGauge, requestCounter)
+
+	rand.Seed(time.Now().UnixNano())
+
+	indexHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		response,_ := client.Get(imageApiUrl)
+		defer response.Body.Close()
+		data,_ := ioutil.ReadAll(response.Body)
+		image := Image{}
+		json.Unmarshal([]byte(data), &image)	
+		tmpl.Execute(w, image)
+		log := AccessLog{
+			ClientIP: r.RemoteAddr,
+		}
+		jsonLog,_ := json.Marshal(log)
+		response,_ = client.Post(logApiUrl, "application/json", bytes.NewBuffer(jsonLog))
+		defer response.Body.Close()
+
+	})
+
+	wrappedIndexHandler := promhttp.InstrumentHandlerInFlight(inFlightGauge,
+						    promhttp.InstrumentHandlerCounter(requestCounter, indexHandler))
+	
+	http.Handle("/", wrappedIndexHandler)
+	http.Handle("/metrics", promhttp.Handler())
+	
+	http.ListenAndServe(":80", nil)
+}