cache: Don't store post data once HTML is generated

cache/getters.go

@@ -42,7 +42,7 @@ func getData(s *store, f FrontEnd) (
 	data interface{}, json []byte, ctr uint64, fresh bool, err error,
 ) {
 	// Have cached data
-	if s.data != nil {
+	if s.json != nil {
 		if s.isFresh() {
 			// No freshness check needed yet
 			return s.data, s.json, s.updateCounter, false, nil
@@ -92,7 +92,7 @@ func GetHTML(k Key, f FrontEnd) ([]byte, uint64, error) {
 	var html []byte
 	genHTML := func() {
 		html = []byte(f.RenderHTML(data, json))
-		s.update(data, json, html)
+		s.update(nil, json, html)
 	}
 	if !fresh {
 		// If the cache has been filled with a JSON request, it will not have

cache/main.go

@@ -98,7 +98,10 @@ func (s *store) update(data interface{}, json, html []byte) {
 	// Calculating the actual memory footprint of the stored post data is
 	// expensive. Assume it is as big as the JSON. Most probably it's far less
 	// than that.
-	newSize := len(json)*2 + len(html)
+	newSize := len(json) + len(html)
+	if data != nil {
+		newSize += len(json)
+	}
 
 	s.data = data
 	s.json = json