Add caching for static web assets

ocis-pkg/middleware/static.go

@@ -1,13 +1,16 @@
 package middleware
 
 import (
+	"fmt"
 	"net/http"
 	"path"
+	"strconv"
 	"strings"
+	"time"
 )
 
 // Static is a middleware that serves static assets.
-func Static(root string, fs http.FileSystem) func(http.Handler) http.Handler {
+func Static(root string, fs http.FileSystem, ttl int) func(http.Handler) http.Handler {
 	if !strings.HasSuffix(root, "/") {
 		root = root + "/"
 	}
@@ -19,6 +22,9 @@ func Static(root string, fs http.FileSystem) func(http.Handler) http.Handler {
 		),
 	)
 
+	// we don't have a last modification date of the static assets, so we use the service start date
+	lastModified := time.Now().UTC().Format(http.TimeFormat)
+
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if strings.HasPrefix(r.URL.Path, path.Join(root, "api")) {
@@ -27,6 +33,9 @@ func Static(root string, fs http.FileSystem) func(http.Handler) http.Handler {
 				if strings.HasSuffix(r.URL.Path, "/") {
 					http.NotFound(w, r)
 				} else {
+					w.Header().Set("Cache-Control", fmt.Sprintf("max-age=%s", strconv.Itoa(ttl)))
+					w.Header().Set("Last-Modified", lastModified)
+					w.Header().Del("Expires")
 					static.ServeHTTP(w, r)
 				}
 			}