Add caching to static files based on etag

cmd/server/main.go

@@ -6,8 +6,10 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"time"
 
 	"forgejo.gwairfelin.com/max/gonotes/internal/conf"
+	"forgejo.gwairfelin.com/max/gonotes/internal/middleware"
 	"forgejo.gwairfelin.com/max/gonotes/internal/notes/views"
 )
 
@@ -24,12 +26,22 @@ func main() {
 	router := http.NewServeMux()
 	notesRouter := views.GetRoutes("/notes")
 
+	cacheExpiration, err := time.ParseDuration("24h")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	etag := middleware.NewETag("static", cacheExpiration)
+
 	router.Handle("/", logger(http.RedirectHandler("/notes/", http.StatusFound)))
 	router.Handle("/notes/", logger(http.StripPrefix("/notes", notesRouter)))
 	router.Handle(
 		"/static/",
 		logger(
-			http.FileServer(http.FS(conf.Static)),
+			middleware.StaticEtagMiddleware(
+				*etag,
+				http.FileServer(http.FS(conf.Static)),
+			),
 		),
 	)
 

internal/middleware/etag_cache.go

@@ -2,7 +2,6 @@ package middleware
 
 import (
 	"fmt"
-	"hash/crc64"
 	"log"
 	"net/http"
 	"strings"
@@ -13,11 +12,8 @@ type ETag struct {
 	Name       string
 	Value      string
 	Expiration time.Duration
-	HashTime   time.Duration
 }
 
-var etags = make([]*ETag, 0)
-
 func (etag *ETag) Header() string {
 	return fmt.Sprintf("\"pb-%s-%s\"", etag.Name, etag.Value)
 }
@@ -46,21 +42,10 @@ func StaticEtagMiddleware(etag ETag, next http.Handler) http.Handler {
 }
 
 // GenerateETagFromBuffer calculates etag value from one or more buffers (e.g. embedded files)
-func GenerateETagFromBuffer(name string, expiration time.Duration, buffers ...[]byte) (*ETag, error) {
+func NewETag(name string, expiration time.Duration) *ETag {
-	start := time.Now()
+	return &ETag{
-	hash := crc64.New(crc64.MakeTable(crc64.ECMA))
-	for _, buffer := range buffers {
-		_, err := hash.Write(buffer)
-		if err != nil {
-			return nil, fmt.Errorf("unable to generate etag from buffer: %w", err)
-		}
-	}
-	etag := &ETag{
 		Name:       name,
 		Expiration: expiration,
-		Value:      fmt.Sprintf("%x", hash.Sum64()),
+		Value:      fmt.Sprintf("%d", time.Now().Unix()),
-		HashTime:   time.Since(start),
 	}
-	etags = append(etags, etag)
-	return etag, nil
 }