public void receive(Client.ResponseOrError<ProtobufResponse> response, List<FastHit> hitsContext) {
        responses.add(new ResponseAndHits(response, hitsContext));
    }
Called by a thread belonging to the client when a valid response becomes available
container-search/src/main/java/com/yahoo/search/dispatch/rpc/RpcProtobufFillInvoker.java