nghttpx: Send GOAWAY for retired h2 backend connection

src/shrpx_http2_session.cc

@@ -171,6 +171,13 @@ void initiate_connection_cb(struct ev_loop *loop, ev_timer *w, int revents) {
 }
 } // namespace
 
+namespace {
+void prepare_cb(struct ev_loop *loop, ev_prepare *w, int revents) {
+  auto http2session = static_cast<Http2Session *>(w->data);
+  http2session->check_retire();
+}
+} // namespace
+
 Http2Session::Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx,
                            Worker *worker,
                            const std::shared_ptr<DownstreamAddrGroup> &group,
@@ -211,6 +218,10 @@ Http2Session::Http2Session(struct ev_loop *loop, SSL_CTX *ssl_ctx,
 
   ev_timer_init(&initiate_connection_timer_, initiate_connection_cb, 0., 0.);
   initiate_connection_timer_.data = this;
+
+  ev_prepare_init(&prep_, prepare_cb);
+  prep_.data = this;
+  ev_prepare_start(loop, &prep_);
 }
 
 Http2Session::~Http2Session() {
@@ -230,6 +241,8 @@ int Http2Session::disconnect(bool hard) {
   conn_.rlimit.stopw();
   conn_.wlimit.stopw();
 
+  ev_prepare_stop(conn_.loop, &prep_);
+
   ev_timer_stop(conn_.loop, &initiate_connection_timer_);
   ev_timer_stop(conn_.loop, &settings_timer_);
   ev_timer_stop(conn_.loop, &connchk_timer_);
@@ -2195,4 +2208,18 @@ void Http2Session::on_timeout() {
   }
 }
 
+void Http2Session::check_retire() {
+  if (!group_->retired) {
+    return;
+  }
+
+  ev_prepare_stop(conn_.loop, &prep_);
+
+  auto last_stream_id = nghttp2_session_get_last_proc_stream_id(session_);
+  nghttp2_submit_goaway(session_, NGHTTP2_FLAG_NONE, last_stream_id,
+                        NGHTTP2_NO_ERROR, nullptr, 0);
+
+  signal_write();
+}
+
 } // namespace shrpx

src/shrpx_http2_session.h

@@ -200,6 +200,11 @@ public:
 
   void on_timeout();
 
+  // This is called periodically using ev_prepare watcher, and if
+  // group_ is retired (backend has been replaced), send GOAWAY to
+  // shutdown the connection.
+  void check_retire();
+
   enum {
     // Disconnected
     DISCONNECTED,
@@ -241,6 +246,7 @@ private:
   ev_timer connchk_timer_;
   // timer to initiate connection.  usually, this fires immediately.
   ev_timer initiate_connection_timer_;
+  ev_prepare prep_;
   DList<Http2DownstreamConnection> dconns_;
   DList<StreamData> streams_;
   std::function<int(Http2Session &)> read_, write_;