Use a timer to try reconnecting to the XMPP server only each 2 seconds

When the connection is lost, immediately try to reconnect, then try to
reconnect every 2 seconds.  This is much better than the previous “Try to
re-connect as fast as possible”.

src/main.cpp

@@ -108,6 +108,8 @@ int main(int ac, char** av)
       exiting = true;
       stop.store(false);
       xmpp_component->shutdown();
+      // Cancel the timer for an potential reconnection
+      TimedEventsManager::instance().cancel("XMPP reconnection");
     }
     if (reload)
     {
@@ -127,17 +129,34 @@ int main(int ac, char** av)
     if (!exiting && xmpp_component->ever_auth &&
         !xmpp_component->is_connected() &&
         !xmpp_component->is_connecting())
-      {
+    {
+      if (xmpp_component->first_connection_try == true)
+      { // immediately re-try to connect
         xmpp_component->reset();
         xmpp_component->start();
       }
+      else
+      { // Re-connecting failed, we now try only each few seconds
+        auto reconnect_later = [xmpp_component]()
+        {
+          xmpp_component->reset();
+          xmpp_component->start();
+        };
+        TimedEvent event(std::chrono::steady_clock::now() + 2s,
+                         reconnect_later, "XMPP reconnection");
+        TimedEventsManager::instance().add_event(std::move(event));
+      }
+    }
     // If the only existing connection is the one to the XMPP component:
     // close the XMPP stream.
     if (exiting && xmpp_component->is_connecting())
       xmpp_component->close();
     if (exiting && p->size() == 1 && xmpp_component->is_document_open())
       xmpp_component->close_document();
-    timeout = TimedEventsManager::instance().get_timeout();
+    if (exiting) // If we are exiting, do not wait for any timed event
+      timeout = utils::no_timeout;
+    else
+      timeout = TimedEventsManager::instance().get_timeout();
   }
   log_info("All connections cleanly closed, have a nice day.");
   return 0;

src/network/poller.cpp

@@ -1,5 +1,6 @@
 #include <network/poller.hpp>
 #include <logger/logger.hpp>
+#include <utils/timed_events.hpp>
 
 #include <assert.h>
 #include <errno.h>
@@ -133,7 +134,7 @@ void Poller::stop_watching_send_events(SocketHandler* socket_handler)
 
 int Poller::poll(const std::chrono::milliseconds& timeout)
 {
-  if (this->socket_handlers.empty())
+  if (this->socket_handlers.empty() && timeout == utils::no_timeout)
     return -1;
 #if POLLER == POLL
   int nb_events = ::poll(this->fds, this->nfds, timeout.count());

src/network/tcp_socket_handler.cpp

@@ -213,8 +213,11 @@ ssize_t TCPSocketHandler::do_recv(void* recv_buf, const size_t buf_size)
   else if (-1 == size)
     {
       log_warning("Error while reading from socket: " << strerror(errno));
+      // Remember if we were connecting, or already connected when this
+      // happened, because close() sets this->connecting to false
+      const auto were_connecting = this->connecting;
       this->close();
-      if (this->connecting)
+      if (were_connecting)
         this->on_connection_failed(strerror(errno));
       else
         this->on_connection_close(strerror(errno));

src/xmpp/xmpp_component.cpp

@@ -39,6 +39,7 @@ static std::set<std::string> kickable_errors{
 XmppComponent::XmppComponent(std::shared_ptr<Poller> poller, const std::string& hostname, const std::string& secret):
   TCPSocketHandler(poller),
   ever_auth(false),
+  first_connection_try(true),
   served_hostname(hostname),
   secret(secret),
   authenticated(false),
@@ -86,6 +87,7 @@ void XmppComponent::send_stanza(const Stanza& stanza)
 
 void XmppComponent::on_connection_failed(const std::string& reason)
 {
+  this->first_connection_try = false;
   log_error("Failed to connect to the XMPP server: " << reason);
 #ifdef SYSTEMDDAEMON_FOUND
   sd_notifyf(0, "STATUS=Failed to connect to the XMPP server: %s", reason.data());
@@ -95,6 +97,7 @@ void XmppComponent::on_connection_failed(const std::string& reason)
 void XmppComponent::on_connected()
 {
   log_info("connected to XMPP server");
+  this->first_connection_try = true;
   XmlNode node("", nullptr);
   node.set_name("stream:stream");
   node["xmlns"] = COMPONENT_NS;

src/xmpp/xmpp_component.hpp

@@ -241,6 +241,12 @@ public:
    * Whether or not we ever succeeded our authentication to the XMPP server
    */
   bool ever_auth;
+  /**
+   * Whether or not this is the first consecutive try on connecting to the
+   * XMPP server.  We use this to delay the connection attempt for a few
+   * seconds, if it is not the first try.
+   */
+  bool first_connection_try;
 
 private:
   /**