feat: use uuids for request ids to guarantee uniqueness

middleware.go

@@ -1,9 +1,10 @@
 package main
 
 import (
-	"math/rand"
 	"net/http"
 	"time"
+
+	"github.com/google/uuid"
 )
 
 // Middleware wraps an http.Handler with additional functionality
@@ -27,13 +28,18 @@ func setResponseHeaders() Middleware {
 func setRequestID() Middleware {
 	return func(h http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			rid := make([]rune, 16)
-			letters := []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
-			for i := range rid {
-				rid[i] = letters[rand.Intn(len(letters))]
+			// NewV7 is used instead of New because the latter will panic
+			// if can't generate a UUID. It's preferably for us to have
+			// worse request ids than panic.
+			uuid, err := uuid.NewV7()
+			var rid string
+			if err != nil {
+				rid = "-"
+			} else {
+				rid = uuid.String()
 			}
 
-			h.ServeHTTP(w, addToContext(r, contextKeyRequestID, string(rid)))
+			h.ServeHTTP(w, addToContext(r, contextKeyRequestID, rid))
 		})
 	}
 }

middleware_test.go

@@ -0,0 +1,30 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+package main
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+func TestRequestIDWellFormed(t *testing.T) {
+	// This method of testing middleware is cribbed from
+	// https://stackoverflow.com/questions/51201056/testing-golang-middleware-that-modifies-the-request
+	nextHandler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		val := r.Context().Value(contextKeyRequestID).(string)
+		if uuid.Validate(val) != nil {
+			t.Errorf("requestID is not a valid uuid! %v", val)
+		}
+	})
+
+	handlerToTest := setRequestID()(nextHandler)
+
+	req := httptest.NewRequest("GET", "http://foo.bar/", nil)
+
+	handlerToTest.ServeHTTP(httptest.NewRecorder(), req)
+}