x @ da217b4426264b3ac4861ce9411bcff61cb3426b

M readme

@@ -5,5 +5,6 @@ Set of packages that I often copy-paste into my new projects.
 
 - is - simple assertion library for tests
 - envy - type-safe os.Getenv with default values
+- reqid - http middleware that add request id header and sets it in context
 
 This repo is MIT Licensed

A reqid/reqid.go

@@ -0,0 +1,63 @@
+package reqid
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"net/http"
+)
+
+type requestIDKey string
+
+const (
+	RequestID requestIDKey = "request-id"
+
+	Header = "X-Request-ID"
+)
+
+// Middleware http middleware that sets random generated request id to each
+// request it get fed.
+func Middleware(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		rid := r.Header.Get(Header)
+		if rid == "" {
+			rid = generateRequestID()
+			r.Header.Set(Header, rid)
+		}
+
+		ctx := SetContext(r.Context(), rid)
+		r = r.WithContext(ctx)
+
+		w.Header().Add(Header, rid)
+		next.ServeHTTP(w, r)
+	})
+}
+
+// Get returns the request ID of http request (looks up from headers)
+func Get(r *http.Request) string {
+	return r.Header.Get(Header)
+}
+
+// GetContext returns the request ID from context.
+func GetContext(ctx context.Context) string {
+	rid, ok := ctx.Value(RequestID).(string)
+	if !ok {
+		return ""
+	}
+	return rid
+}
+
+// SetContext gets a parent context and returns a child context with the set
+// provided request ID
+func SetContext(ctx context.Context, reqID string) context.Context {
+	return context.WithValue(ctx, RequestID, reqID)
+}
+
+func generateRequestID() string {
+	b := make([]byte, 13)
+	_, err := rand.Read(b)
+	if err != nil {
+		return "unknown"
+	}
+	return hex.EncodeToString(b)
+}

A reqid/reqid_test.go

@@ -0,0 +1,39 @@
+package reqid
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"olexsmir.xyz/x/is"
+)
+
+func TestMiddleware(t *testing.T) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /", testHandler)
+	hand := Middleware(mux)
+
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/", nil)
+	hand.ServeHTTP(w, req)
+
+	is.Equal(t, http.StatusOK, w.Code)
+	is.NotEqual(t, w.Header().Get(Header), "")
+}
+
+func BenchmarkMiddleware(b *testing.B) {
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /", testHandler)
+	hand := Middleware(mux)
+
+	w := httptest.NewRecorder()
+	req, _ := http.NewRequest(http.MethodGet, "/", nil)
+
+	for b.Loop() {
+		hand.ServeHTTP(w, req)
+	}
+}
+
+func testHandler(w http.ResponseWriter, _ *http.Request) {
+	w.WriteHeader(http.StatusOK)
+}