Created
April 5, 2018 21:53
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package main | |
import ( | |
"net/http" | |
"fmt" | |
"io/ioutil" | |
"math/rand" | |
) | |
var letters = []byte("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ") | |
const HEADER_CORRELATION_ID = "correlationId" | |
type Frontend struct { | |
client *http.Client | |
} | |
func NewFrontend() *Frontend { | |
return &Frontend{client: &http.Client{}} | |
} | |
func (f *Frontend) ServeHTTP(w http.ResponseWriter, r *http.Request) { | |
var correlationId = r.Header.Get(HEADER_CORRELATION_ID) | |
if correlationId == "" { | |
correlationId = newCorrelationId() | |
} | |
request, err := http.NewRequest("GET", "http://localhost:8082/url", nil) | |
request.Header.Set(HEADER_CORRELATION_ID, correlationId) | |
//resp, err := http.Get("http://localhost:8082/url") | |
resp, err := f.client.Do(request) | |
if err != nil { | |
panic(err) | |
} | |
defer resp.Body.Close() | |
body, err := ioutil.ReadAll(resp.Body) | |
if err != nil { | |
panic(err) | |
} | |
fmt.Fprint(w, "Hello (frontend)\n") | |
w.Write(body) | |
} | |
func randSeq(n int) string { | |
b := make([]byte, n) | |
for i := range b { | |
b[i] = letters[rand.Intn(len(letters))] | |
} | |
return string(b) | |
} | |
func newCorrelationId() string { | |
return randSeq(16) | |
} | |
func backendHandler(w http.ResponseWriter, r *http.Request) { | |
var correlationId = r.Header.Get(HEADER_CORRELATION_ID) | |
fmt.Fprint(w, "Hello (backend)\n") | |
fmt.Fprintf(w, "Correlation ID: %s\n", correlationId) | |
} | |
func main() { | |
// backend service | |
var backendService *http.ServeMux = http.NewServeMux() | |
backendService .HandleFunc("/", backendHandler) | |
go http.ListenAndServe(":8082", backendService) | |
// frontend service | |
var frontendService = http.NewServeMux() | |
frontendService.Handle("/", NewFrontend()) | |
http.ListenAndServe(":8081", frontendService) | |
} |
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