[GitHub] [trafficserver] maskit commented on a change in pull request #7622: HTTP/2 to origin

[GitBox <gi...@apache.org>]

maskit commented on a change in pull request #7622:
URL: https://github.com/apache/trafficserver/pull/7622#discussion_r677061238



##########
File path: proxy/http/HttpSM.cc
##########
@@ -289,6 +277,160 @@ HttpVCTable::cleanup_all()
   }
 }
 
+class ConnectingEntry : public Continuation
+{
+public:
+  std::set<HttpSM *> _connect_sms;
+  NetVConnection *_netvc        = nullptr;
+  IOBufferReader *_netvc_reader = nullptr;
+  MIOBuffer *_netvc_read_buffer = nullptr;
+  std::string sni;
+  std::string cert_name;
+  IpEndpoint _ipaddr;
+  std::string hostname;
+  Action *_pending_action = nullptr;
+  NetVCOptions opt;
+
+  void remove_entry();
+  int state_http_server_open(int event, void *data);
+  static PoolableSession *create_server_session(HttpSM *root_sm, NetVConnection *netvc, MIOBuffer *netvc_read_buffer,
+                                                IOBufferReader *netvc_reader);
+};
+
+struct IpHelper {
+  size_t
+  operator()(IpEndpoint const &arg) const
+  {
+    return IpAddr{&arg.sa}.hash();
+  }
+  bool
+  operator()(IpEndpoint const &arg1, IpEndpoint const &arg2) const
+  {
+    return ats_ip_addr_port_eq(&arg1.sa, &arg2.sa);
+  }
+};
+using ConnectingIpPool = std::unordered_multimap<IpEndpoint, ConnectingEntry *, IpHelper>;
+
+class ConnectingPool
+{
+public:
+  ConnectingPool() {}
+  ConnectingIpPool m_ip_pool;
+};
+
+void
+initialize_thread_for_connecting_pools(EThread *thread)
+{
+  if (thread->connecting_pool == nullptr) {
+    thread->connecting_pool = new ConnectingPool();
+  }
+}
+
+int
+ConnectingEntry::state_http_server_open(int event, void *data)
+{
+  Debug("http_connect", "entered inside ConnectingEntry::state_http_server_open");
+
+  switch (event) {
+  case NET_EVENT_OPEN: {
+    _netvc                 = static_cast<NetVConnection *>(data);
+    UnixNetVConnection *vc = static_cast<UnixNetVConnection *>(_netvc);
+    ink_release_assert(_pending_action == nullptr || _pending_action->continuation == vc->get_action()->continuation);
+    _pending_action = nullptr;
+    Debug("http_connect", "ConnectingEntrysetting handler for TCP handshake");
+    // Just want to get a write-ready event so we know that the TCP handshake is complete.
+    // The buffer we create will be handed over to the eventually created server session
+    _netvc_read_buffer = new_MIOBuffer(HTTP_SERVER_RESP_HDR_BUFFER_INDEX);
+    _netvc_reader      = _netvc_read_buffer->alloc_reader();
+    _netvc->do_io_write(this, 1, _netvc_reader);
+    ink_release_assert(!_connect_sms.empty());
+    if (!_connect_sms.empty()) {
+      HttpSM *prime_connect_sm = *(_connect_sms.begin());
+      _netvc->set_inactivity_timeout(prime_connect_sm->get_server_connect_timeout());
+    }
+    ink_release_assert(_pending_action == nullptr);
+    return 0;
+  }
+  case VC_EVENT_READ_COMPLETE:
+  case VC_EVENT_WRITE_READY:
+  case VC_EVENT_WRITE_COMPLETE: {
+    Debug("http_connect", "Kick off %" PRId64 " state machines waiting for origin", _connect_sms.size());
+    this->remove_entry();
+    _netvc->do_io_write(nullptr, 0, nullptr);
+    if (!_connect_sms.empty()) {
+      auto prime_iter = _connect_sms.rbegin();
+      ink_release_assert(prime_iter != _connect_sms.rend());
+      PoolableSession *new_session = (*prime_iter)->create_server_session(_netvc, _netvc_read_buffer, _netvc_reader);
+      _netvc                       = nullptr;
+
+      // Did we end up with a multiplexing session?
+      int count = 0;
+      if (new_session->is_multiplexing()) {
+        // Hand off to all queued up ConnectSM's.

Review comment:
       > Actually, I think the code will pull new transactions under the reported max_concurrent_streams setting.
   
   I don't really understand this part. On the example above, the origin server tells us "max_concurrent_streams is 2" on the first connection. The origin server doesn't want to take the third request until either of the first two transactions ends. But we exploit a loophole and start third request by opening a new connection. I think this is the scenario that the paragraph on RFC7540 tries to avoid.




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