MDEV-33990: SHOW STATUS counts ER_CON_COUNT_ERROR as Connection_errors_internal

Bring info about cause of closing connection in the place where we increment
statistics to do it correctly.

mysql-test/main/connect.result

@@ -444,3 +444,33 @@ FOUND 2 /This connection closed normally without authentication/ in mysqld.1.err
 SET GLOBAL log_warnings=default;
 SET GLOBAL connect_timeout= @save_connect_timeout;
 # End of 10.4 tests
+#
+# MDEV-33990: SHOW STATUS counts ER_CON_COUNT_ERROR as
+# Connection_errors_internal
+#
+flush status;
+show global status like 'Connection_errors%';
+Variable_name	Value
+Connection_errors_accept	0
+Connection_errors_internal	0
+Connection_errors_max_connections	0
+Connection_errors_peer_address	0
+Connection_errors_select	0
+Connection_errors_tcpwrap	0
+set @max_con.save= @@max_connections;
+set global max_connections= 10;
+# ERROR 1040
+# ERROR 1040
+connection default;
+show global status like 'Connection_errors%';
+Variable_name	Value
+Connection_errors_accept	0
+Connection_errors_internal	0
+Connection_errors_max_connections	2
+Connection_errors_peer_address	0
+Connection_errors_select	0
+Connection_errors_tcpwrap	0
+set global max_connections= @max_con.save;
+#
+# End of 10.5 tests
+#

mysql-test/main/connect.test

@@ -508,3 +508,38 @@ SET GLOBAL log_warnings=default;
 SET GLOBAL connect_timeout= @save_connect_timeout;
 
 --echo # End of 10.4 tests
+
+--echo #
+--echo # MDEV-33990: SHOW STATUS counts ER_CON_COUNT_ERROR as
+--echo # Connection_errors_internal
+--echo #
+
+flush status;
+
+show global status like 'Connection_errors%';
+
+set @max_con.save= @@max_connections;
+set global max_connections= 10;
+
+--disable_result_log
+--disable_query_log
+--let $n= 12
+while ($n)
+{
+  --error 0,ER_CON_COUNT_ERROR
+  --connect (con$n,localhost,root)
+  if ($mysql_errno) {
+    --echo # ERROR $mysql_errno
+  }
+  --dec $n
+}
+
+--enable_result_log
+--enable_query_log
+--connection default
+show global status like 'Connection_errors%';
+set global max_connections= @max_con.save;
+
+--echo #
+--echo # End of 10.5 tests
+--echo #

sql/sql_connect.cc

@@ -1362,7 +1362,7 @@ void do_handle_one_connection(CONNECT *connect, bool put_in_cache)
   THD *thd;
   if (!(thd= connect->create_thd(NULL)))
   {
-    connect->close_and_delete();
+    connect->close_and_delete(0);
     return;
   }
 
@@ -1437,7 +1437,7 @@ void do_handle_one_connection(CONNECT *connect, bool put_in_cache)
     if (!(connect->create_thd(thd)))
     {
       /* Out of resources. Free thread to get more resources */
-      connect->close_and_delete();
+      connect->close_and_delete(0);
       break;
     }
     delete connect;
@@ -1466,9 +1466,11 @@ void do_handle_one_connection(CONNECT *connect, bool put_in_cache)
   Close connection without error and delete the connect object
   This and close_with_error are only called if we didn't manage to
   create a new thd object.
+
+  Note: err can be 0 if unknown/not inportant
 */
 
-void CONNECT::close_and_delete()
+void CONNECT::close_and_delete(uint err)
 {
   DBUG_ENTER("close_and_delete");
 
@@ -1482,6 +1484,10 @@ void CONNECT::close_and_delete()
   vio_type= VIO_CLOSED;
 
   --*scheduler->connection_count;
+
+  if (err == ER_CON_COUNT_ERROR)
+    statistic_increment(connection_errors_max_connection, &LOCK_status);
+  else
     statistic_increment(connection_errors_internal, &LOCK_status);
   statistic_increment(aborted_connects,&LOCK_status);
 
@@ -1506,7 +1512,7 @@ void CONNECT::close_with_error(uint sql_errno,
     delete thd;
     set_current_thd(0);
   }
-  close_and_delete();
+  close_and_delete(close_error);
 }
 
 

sql/sql_connect.h

@@ -61,7 +61,7 @@ class CONNECT : public ilink {
     count--;
     DBUG_ASSERT(vio_type == VIO_CLOSED);
   }
-  void close_and_delete();
+  void close_and_delete(uint err);
   void close_with_error(uint sql_errno,
                         const char *message, uint close_error);
   THD *create_thd(THD *thd);

sql/threadpool_common.cc

@@ -241,7 +241,7 @@ static THD* threadpool_add_connection(CONNECT *connect, void *scheduler_data)
   if (!mysys_var ||!(thd= connect->create_thd(NULL)))
   {
     /* Out of memory? */
-    connect->close_and_delete();
+    connect->close_and_delete(0);
     if (mysys_var)
       my_thread_end();
     return NULL;
@@ -417,7 +417,7 @@ static void tp_add_connection(CONNECT *connect)
   if (c)
     pool->add(c);
   else
-    connect->close_and_delete();
+    connect->close_and_delete(0);
 }
 
 int tp_get_idle_thread_count()