sends default trailers only for http2 requests

src/clj/qbits/jet/servlet.clj

@@ -283,7 +283,9 @@
           ^Request servlet-request (:servlet-request request-map)
           servlet-response  (.getServletResponse servlet-request)]
       (when (and trailers (instance? Response servlet-response))
-        (.setTrailers ^Response servlet-response (util/trailers-ch->supplier trailers)))
+        (let [request-protocol (some-> servlet-request .getProtocol)
+              http2? (util/http2-request? request-protocol)]
+          (.setTrailers ^Response servlet-response (util/trailers-ch->supplier trailers http2?))))
       (set-status+headers! servlet-response request-map status headers)
       (set-body! servlet-response request-map body)))
 

src/clj/qbits/jet/util.clj

@@ -51,19 +51,16 @@
         (when-let [trailers (trailers-fn)]
           (map->http-fields trailers))))))
 
-(defn- map->non-empty-http-fields
-  "Ensures that we return on-empty http fields as trailers in responses.
-   This is to prevent issues while using clients who do not accept empty trailers in responses."
-  ;; TODO remove when https://github.com/eclipse/jetty.project/issues/3829 is fixed and empty trailer frames are not sent.
-  [trailers-map]
-  (if (seq trailers-map)
-    (map->http-fields trailers-map)
-    (map->http-fields {"x-waiter-trailer-reason" "ensures-non-empty-trailers"})))
-
 (defn trailers-ch->supplier
-  [trailers-ch]
+  [trailers-ch http2?]
   (when trailers-ch
     (reify Supplier
       (get [_]
-        (map->non-empty-http-fields (async/<!! trailers-ch))))))
-
+        (let [trailers-map (async/<!! trailers-ch)]
+          (if (seq trailers-map)
+            (map->http-fields trailers-map)
+            (when http2?
+              ;; Ensures that we return on-empty http fields as trailers in responses.
+              ;; This is to prevent issues while using http2 clients who do not accept empty trailers in responses.
+              ;; TODO remove when https://github.com/eclipse/jetty.project/issues/3829 is fixed and empty trailer frames are not sent.
+              (map->http-fields {"x-waiter-trailer-reason" "ensures-non-empty-trailers"}))))))))