nghttpx: Read from backend eagerly in all upstreams

src/shrpx_http2_upstream.cc

@@ -1006,7 +1006,8 @@ ssize_t downstream_data_read_callback(nghttp2_session *session,
 
   auto dconn = downstream->get_downstream_connection();
 
-  if (body->rleft() == 0 && dconn) {
+  if (body->rleft() == 0 && dconn &&
+      downstream->get_response_state() != Downstream::MSG_COMPLETE) {
     // Try to read more if buffer is empty.  This will help small
     // buffer and make priority handling a bit better.
     if (upstream->downstream_read(dconn) != 0) {

src/shrpx_https_upstream.cc

@@ -391,7 +391,14 @@ int HttpsUpstream::on_write() {
   if (!downstream) {
     return 0;
   }
+  auto dconn = downstream->get_downstream_connection();
   auto wb = handler_->get_wb();
+  if (wb->rleft() == 0 && dconn &&
+      downstream->get_response_state() != Downstream::MSG_COMPLETE) {
+    if (downstream_read(dconn) != 0) {
+      return -1;
+    }
+  }
   struct iovec iov[2];
   auto iovcnt = wb->wiovec(iov);
   if (iovcnt == 0) {

src/shrpx_spdy_upstream.cc

@@ -704,6 +704,17 @@ ssize_t spdy_data_read_callback(spdylay_session *session, int32_t stream_id,
   auto body = downstream->get_response_buf();
   assert(body);
 
+  auto dconn = downstream->get_downstream_connection();
+
+  if (body->rleft() == 0 && dconn &&
+      downstream->get_response_state() != Downstream::MSG_COMPLETE) {
+    // Try to read more if buffer is empty.  This will help small
+    // buffer and make priority handling a bit better.
+    if (upstream->downstream_read(dconn) != 0) {
+      return SPDYLAY_ERR_CALLBACK_FAILURE;
+    }
+  }
+
   auto nread = body->remove(buf, length);
   auto body_empty = body->rleft() == 0;