package main
import (
"bytes"
"encoding/json"
"errors"
"fmt"
"github.com/gorilla/handlers"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/promauto"
"github.com/prometheus/client_golang/prometheus/promhttp"
"io"
"log"
"net/http"
"os"
"strconv"
)
func getenv(key, fallback string) string {
value := os.Getenv(key)
if len(value) == 0 {
return fallback
}
return value
}
type Comment struct {
Comment string `json:"comment"`
}
type EngineError struct {
Message string `json:"message"`
AdditionalInfo string `json:"additionalInfo"`
}
var comments_engine_endpoint string
var (
httpHits = promauto.NewCounterVec(prometheus.CounterOpts{
Name: "comments_interactor_http_hits_total",
Help: "The total number of hits on a given route",
}, []string{"route", "method"})
commentsReceived = promauto.NewCounter(prometheus.CounterOpts{
Name: "comments_interactor_comments_received_total",
Help: "The total number of comments received (successfully posted or not)",
})
commentsPosted = promauto.NewCounter(prometheus.CounterOpts{
Name: "comments_interactor_comments_posted_total",
Help: "The total number of comments posted (successfully posted)",
})
)
func sendComment(w http.ResponseWriter, r *http.Request) {
commentsReceived.Inc()
if err := r.ParseForm(); err != nil {
fmt.Fprintf(w, "error
ParseForm() err: %v
", err)
return
}
var comment Comment
comment.Comment = r.FormValue("comment")
if comment.Comment == "" {
fmt.Fprintf(w, "error
Empty comment or malformed
")
return
}
obj, err := json.Marshal(comment)
if err != nil {
fmt.Fprintf(w, "error
Empty comment or malformed
")
return
}
_, err = http.Post("http://"+comments_engine_endpoint+"/comment", "application/json", bytes.NewReader(obj))
if err == nil {
fmt.Fprintf(w, "Success !
Comment posted
")
commentsPosted.Inc()
} else {
fmt.Fprintf(w, "Error
Error while trying to send a comment: %s", err)
}
}
func showDashboard(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "
Latest comments
")
io.WriteString(w, "")
resp, err := http.Get("http://" + comments_engine_endpoint + "/latest")
if err != nil {
log.Printf("Could not HTTP get on CommentsEngine: %s", err)
io.WriteString(w, fmt.Sprintf("Error contacting the backend, %s", err))
} else {
defer resp.Body.Close()
body, err := io.ReadAll(resp.Body)
var comments []string
err = json.Unmarshal(body, &comments)
if err != nil {
var engineError EngineError
err = json.Unmarshal(body, &engineError)
if err != nil {
log.Printf("CommentsEngine returned unexpected value: %s", err)
io.WriteString(w, fmt.Sprintf("CommentsEngine returned badly formated values, %s", err))
} else {
io.WriteString(w, fmt.Sprintf("CommentsEngine returned an error: %s
Additional info: %s", engineError.Message, engineError.AdditionalInfo))
}
} else {
for i, comment := range comments {
io.WriteString(w, "
comment "+strconv.Itoa(i)+"
"+comment+"
Send comment
")
io.WriteString(w, "")
}
func getRoot(w http.ResponseWriter, r *http.Request) {
httpHits.With(prometheus.Labels{"route": "/", "method": r.Method}).Inc()
io.WriteString(w, "CommentsInteractor")
if r.Method == http.MethodPost {
sendComment(w, r)
}
showDashboard(w, r)
io.WriteString(w, "")
}
func sendError(w http.ResponseWriter, err error, additionalInfo string) {
w.WriteHeader(http.StatusInternalServerError)
resp := make(map[string]string)
resp["message"] = fmt.Sprint(err)
resp["additionalInfo"] = additionalInfo
jsonResp, err := json.Marshal(resp)
if err != nil {
log.Fatalf("Error happened in JSON marshal. Err: %s", err)
}
w.Write(jsonResp)
}
func main() {
http.HandleFunc("/", getRoot)
prometheus.Unregister(prometheus.NewGoCollector())
http.Handle("/metrics", promhttp.Handler())
listeningHostPort := getenv("HOST", "127.0.0.1") + ":" + getenv("PORT", "9000")
comments_engine_endpoint = getenv("COMMENTS_ENGINE_ENDPOINT", "127.0.0.1:8000")
fmt.Printf("Starting the server on %s\n", listeningHostPort)
err := http.ListenAndServe(listeningHostPort, handlers.LoggingHandler(os.Stdout, http.DefaultServeMux))
if errors.Is(err, http.ErrServerClosed) {
fmt.Printf("server closed\n")
} else if err != nil {
fmt.Printf("error starting server: %s\n", err)
os.Exit(1)
}
}