mock API infrastructure

docker-compose.yml

version: '3.5'

services:
  api:
    build: /Users/maurorappa/mockapi
    restart: always
    ports:
      - 8081:8081
    environment:
      PORT: 8081
      BACKEND1: 172.17.0.1:8082
      BACKEND2: 172.17.0.1:8083
    healthcheck:
      test: ["CMD", "wget" ,"-q", "-O", "/dev/null", "http://localhost:8081/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 60s
  api2:
    build: /Users/maurorappa/mockapi
    restart: always
    ports:
      - 8082:8082
    environment:
      PORT: 8082
      BACKEND1: 172.17.0.1:8084
    healthcheck:
      test: ["CMD", "wget" ,"-q", "-O", "/dev/null", "http://localhost:8082/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 60s
  api3:
    build: /Users/maurorappa/mockapi
    restart: always
    ports:
      - 8083:8083
    environment:
      PORT: 8083
      BACKEND1: 172.17.0.1:8084
      BACKEND2: 172.17.0.1:8085
    healthcheck:
      test: ["CMD", "wget" ,"-q", "-O", "/dev/null", "http://localhost:8083/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 60s
  api4:
    build: /Users/maurorappa/mockapi
    restart: always
    ports:
      - 8084:8084
    environment:
      PORT: 8084
    healthcheck:
      test: ["CMD", "wget" ,"-q", "-O", "/dev/null", "http://localhost:8084/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 60s
  api5:
    build: /Users/maurorappa/mockapi
    restart: always
    ports:
      - 8085:8085
    environment:
      PORT: 8085
      BACKEND1: 172.17.0.1:8083
    healthcheck:
      test: ["CMD", "wget" ,"-q", "-O", "/dev/null", "http://localhost:8085/health"]
      interval: 30s
      timeout: 10s
      retries: 3
      start_period: 60s

Dockerfile

FROM golang:buster as builder
WORKDIR /go/src/mockApi
COPY . /go/src/mockApi
RUN go get github.com/gorilla/mux
RUN CGO_ENABLED=0 GOOS=linux go build -o mock_api *.go

FROM busybox:latest
COPY --from=builder /go/src/mockApi/mock_api /bin/mock_api
RUN chmod +x /bin/mock_api

ENTRYPOINT [ "/bin/mock_api" ]

mock_api.go

package main

import (
	"crypto/ecdsa"
	"crypto/elliptic"
	cr "crypto/rand"
	"crypto/sha256"
	"fmt"
	"github.com/gorilla/mux"
	"io/ioutil"
	"log"
	"math/rand"
	"net/http"
	"os"
	"strconv"
	"time"
)

var (
	listenPort string
	serverA    string
	serverB    string
)

func init() {
	rand.Seed(time.Now().UTC().UnixNano())
	listenPort = os.Getenv("PORT")
	serverA = os.Getenv("BACKEND1")
	serverB = os.Getenv("BACKEND2")
}

func home(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "Welcome to the Test API server")
}

func health(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
}

func number(w http.ResponseWriter, r *http.Request) {
	rnd := rand.Intn(1000)
	log.Println("generated ", rnd)
	fmt.Fprintf(w, "%d", rnd)
}

func callremote(server string) (number string) {
	res, err := http.Get("http://" + server + "/number")
	if err != nil {
		log.Println(err)
	}
	remote, err := ioutil.ReadAll(res.Body)
	res.Body.Close()
	return string(remote)
}

func callbckend1(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "%s", callremote(serverA))
}

func callbckend2(w http.ResponseWriter, r *http.Request) {
	fmt.Fprintf(w, "%s", callremote(serverB))
}

func sumbckends(w http.ResponseWriter, r *http.Request) {
	a, _ := strconv.Atoi(callremote(serverA))
	b, _ := strconv.Atoi(callremote(serverB))
	c := a + b
	log.Println("sum: ", c)
	fmt.Fprintf(w, "%s", strconv.Itoa(c))
}

func crypt(w http.ResponseWriter, r *http.Request) {
	privateKey, _ := ecdsa.GenerateKey(elliptic.P521(), cr.Reader)
	msg := "hello, world"
	hash := sha256.Sum256([]byte(msg))

	rnd, bigint, _ := ecdsa.Sign(cr.Reader, privateKey, hash[:])
	signature := fmt.Sprintf("0x%x, 0x%x", rnd, bigint)
	fmt.Fprintln(w, signature)
	valid := ecdsa.Verify(&privateKey.PublicKey, hash[:], rnd, bigint)
	fmt.Fprintln(w, "signature verified:", valid)

}
func main() {
	log.Println("listening to " + listenPort + "...")
	router := mux.NewRouter().StrictSlash(true)
	router.HandleFunc("/", home)
	router.HandleFunc("/health", health)
	router.HandleFunc("/number", number)
	router.HandleFunc("/callbackend1", callbckend1)
	router.HandleFunc("/callbackend2", callbckend2)
	router.HandleFunc("/sumbackends", sumbckends)
	router.HandleFunc("/crypt", crypt)
	log.Fatal(http.ListenAndServe(":"+listenPort, router))
}