client id middleware

http/middleware/response_header.go

@@ -0,0 +1,112 @@
+// Copyright © 2021 by PACE Telematics GmbH. All rights reserved.
+// Created at 2021/05/10 by Alessandro Miceli
+
+
+package middleware
+
+import (
+	"context"
+	"net/http"
+	"strings"
+	"sync"
+
+	"github.com/pace/bricks/maintenance/log"
+)
+
+// ClientIDHeaderName name of the HTTP header that is used for reporting
+const ClientIDHeaderName = "Client-ID"
+
+// ResponseClientID middleware to report client ID
+func ResponseClientID(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var rcc ResponseClientIDContext
+		rcw := responseClientIDWriter{
+			ResponseWriter: w,
+			rcc:            &rcc,
+		}
+
+		r = r.WithContext(ContextWithResponseClientID(r.Context(), &rcc))
+		next.ServeHTTP(&rcw, r)
+	})
+}
+
+func AddResponseClientID(ctx context.Context, clientID string) {
+	cIDc := ResponseClientIDContextFromContext(ctx)
+	if cIDc == nil {
+		log.Ctx(ctx).Warn().Msgf("can't add client %s, because context is missing", clientID)
+		return
+	}
+	cIDc.AddResponseClientID(clientID)
+}
+
+type responseClientIDWriter struct {
+	http.ResponseWriter
+	header bool
+	rcc    *ResponseClientIDContext
+}
+
+// addHeader adds the clientID header if not done already
+func (w *responseClientIDWriter) addHeader() {
+	if len(w.rcc.clientIDs) > 0 {
+		w.ResponseWriter.Header().Add(ClientIDHeaderName, w.rcc.String())
+	}
+	w.header = true
+}
+
+func (w *responseClientIDWriter) Write(data []byte) (int, error) {
+	w.addHeader()
+	return w.ResponseWriter.Write(data)
+}
+
+// ContextWithResponseClientID creates a contex with the provided client ID
+func ContextWithResponseClientID(ctx context.Context, rcc *ResponseClientIDContext) context.Context {
+	return context.WithValue(ctx, (*ResponseClientIDContext)(nil), rcc)
+}
+
+// ResponseClientIDContextFromContext returns the client ID context or nil
+func ResponseClientIDContextFromContext(ctx context.Context) *ResponseClientIDContext {
+	if v := ctx.Value((*ResponseClientIDContext)(nil)); v != nil {
+		return v.(*ResponseClientIDContext)
+	}
+	return nil
+}
+
+// ResponseClientIDContext contains all client IDs that were seen
+// during the request livecycle
+type ResponseClientIDContext struct {
+	mu        sync.RWMutex
+	clientIDs []responseClientID
+}
+
+func (rcc *ResponseClientIDContext) AddResponseClientID(clientID string) {
+	rcc.mu.Lock()
+	rcc.clientIDs = append(rcc.clientIDs, responseClientID{
+		ClientID: clientID,
+	})
+	rcc.mu.Unlock()
+}
+
+// String formats all client IDs
+func (rcc *ResponseClientIDContext) String() string {
+	var b strings.Builder
+	sep := len(rcc.clientIDs) - 1
+	for _, dep := range rcc.clientIDs {
+		b.WriteString(dep.String())
+		if sep > 0 {
+			b.WriteByte(',')
+			sep--
+		}
+	}
+	return b.String()
+}
+
+// responseClientID represents the client ID that
+// was sent in the request
+type responseClientID struct {
+	ClientID string //client ID name
+}
+
+// String return a client ID
+func (rcc responseClientID) String() string {
+	return rcc.ClientID
+}

http/middleware/response_header_test.go

@@ -0,0 +1,58 @@
+// Copyright © 2021 by PACE Telematics GmbH. All rights reserved.
+// Created at 2021/05/10 by Alessandro Miceli
+
+package middleware
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_ResponseClientID_Middleare(t *testing.T) {
+	AddResponseClientID(context.TODO(), "test") // should not fail
+	t.Run("empty set", func(t *testing.T) {
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/", nil)
+
+		h := ResponseClientID(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		}))
+		h.ServeHTTP(rec, req)
+		assert.Nil(t, rec.Result().Header[http.CanonicalHeaderKey(ClientIDHeaderName)])
+	})
+	t.Run("one client set", func(t *testing.T) {
+		rec := httptest.NewRecorder()
+		req := httptest.NewRequest(http.MethodGet, "/", nil)
+
+		h := ResponseClientID(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			AddResponseClientID(r.Context(), "test")
+			w.Write(nil) // nolint: errcheck
+		}))
+		h.ServeHTTP(rec, req)
+		assert.Equal(t, rec.Result().Header[http.CanonicalHeaderKey(ClientIDHeaderName)][0], "test")
+	})
+}
+
+func Test_ResponseClientIDContext_String(t *testing.T) {
+	var rcc ResponseClientIDContext
+
+	// empty
+	assert.Empty(t, rcc.String())
+
+	// one dependency
+	rcc.AddResponseClientID("test1")
+	assert.EqualValues(t, "test1", rcc.String())
+
+	// multiple dependencies
+	rcc.AddResponseClientID("test2")
+	assert.EqualValues(t, "test1,test2", rcc.String())
+
+	rcc.AddResponseClientID("test3")
+	assert.EqualValues(t, "test1,test2,test3", rcc.String())
+
+	rcc.AddResponseClientID("test4")
+	assert.EqualValues(t, "test1,test2,test3,test4", rcc.String())
+}