nghttpx: Don't write again after failure

Plain write(2) is OK, but SSL_write requires same arguments on retry.
It would be better to avoid calling them again.

src/shrpx_http2_session.cc

@@ -2026,7 +2026,7 @@ int Http2Session::write_clear() {
         // contain part of response body.  So keep reading.  Invoke
         // read event to get read(2) error just in case.
         ev_feed_event(conn_.loop, &conn_.rev, EV_READ);
-        wb_.drain(wb_.rleft());
+        write_ = &Http2Session::write_void;
         break;
       }
 
@@ -2141,7 +2141,7 @@ int Http2Session::write_tls() {
         // contain part of response body.  So keep reading.  Invoke
         // read event to get read(2) error just in case.
         ev_feed_event(conn_.loop, &conn_.rev, EV_READ);
-        wb_.drain(wb_.rleft());
+        write_ = &Http2Session::write_void;
         break;
       }
 
@@ -2165,6 +2165,11 @@ int Http2Session::write_tls() {
   return 0;
 }
 
+int Http2Session::write_void() {
+  conn_.wlimit.stopw();
+  return 0;
+}
+
 bool Http2Session::should_hard_fail() const {
   switch (state_) {
   case PROXY_CONNECTING:

src/shrpx_http2_session.h

@@ -114,6 +114,9 @@ public:
   int tls_handshake();
   int read_tls();
   int write_tls();
+  // This is a special write function which just stop write event
+  // watcher.
+  int write_void();
 
   int downstream_read_proxy(const uint8_t *data, size_t datalen);
   int downstream_connect_proxy();

src/shrpx_http_downstream_connection.cc

@@ -200,7 +200,8 @@ HttpDownstreamConnection::HttpDownstreamConnection(
       ioctrl_(&conn_.rlimit),
       response_htp_{0},
       initial_addr_idx_(initial_addr_idx),
-      reuse_first_write_done_(true) {}
+      reuse_first_write_done_(true),
+      reusable_(true) {}
 
 HttpDownstreamConnection::~HttpDownstreamConnection() {
   if (LOG_ENABLED(INFO)) {
@@ -1157,7 +1158,8 @@ int HttpDownstreamConnection::write_clear() {
       // part of response body.  So keep reading.  Invoke read event
       // to get read(2) error just in case.
       ev_feed_event(conn_.loop, &conn_.rev, EV_READ);
-      input->drain(input->rleft());
+      do_write_ = &HttpDownstreamConnection::noop;
+      reusable_ = false;
       break;
     }
 
@@ -1285,7 +1287,8 @@ int HttpDownstreamConnection::write_tls() {
       // part of response body.  So keep reading.  Invoke read event
       // to get read(2) error just in case.
       ev_feed_event(conn_.loop, &conn_.rev, EV_READ);
-      input->drain(input->rleft());
+      do_write_ = &HttpDownstreamConnection::noop;
+      reusable_ = false;
       break;
     }
 
@@ -1445,7 +1448,9 @@ HttpDownstreamConnection::get_downstream_addr_group() const {
 
 DownstreamAddr *HttpDownstreamConnection::get_addr() const { return addr_; }
 
-bool HttpDownstreamConnection::poolable() const { return !group_->retired; }
+bool HttpDownstreamConnection::poolable() const {
+  return !group_->retired && reusable_;
+}
 
 const Address *HttpDownstreamConnection::get_raddr() const { return raddr_; }
 

src/shrpx_http_downstream_connection.h

@@ -112,6 +112,8 @@ private:
   // true if first write of reused connection succeeded.  For
   // convenience, this is initialized as true.
   bool reuse_first_write_done_;
+  // true if this object can be reused
+  bool reusable_;
 };
 
 } // namespace shrpx