MDEV-7500 thread_handling option in my.cnf is not passing "connect events" to audit plugin.

  The MYSQL_AUDIT_NOTIFY_CONNECTION_CONNECT() call moved to the login_connection()
  function. So that it'll be invoked in any thread handling mode.

mysql-test/suite/plugins/t/thread_pool_server_audit.opt

+--thread_handling=pool-of-threads
+

mysql-test/suite/plugins/t/thread_pool_server_audit.test

+--source include/not_embedded.inc
+--source include/have_pool_of_threads.inc
+
+if (!$SERVER_AUDIT_SO) {
+  skip No SERVER_AUDIT plugin;
+}
+
+install plugin server_audit soname 'server_audit';
+
+show variables like 'server_audit%';
+set global server_audit_file_path=null;
+set global server_audit_incl_users=null;
+set global server_audit_file_path='server_audit.log';
+set global server_audit_output_type=file;
+set global server_audit_logging=on;
+connect (con1,localhost,root,,mysql);
+connection default;
+disconnect con1;
+--sleep 2
+--sleep 2
+--replace_result $MASTER_MYSOCK MASTER_SOCKET $MASTER_MYPORT MASTER_PORT
+--error ER_ACCESS_DENIED_ERROR
+connect (con1,localhost,no_such_user,,mysql);
+connection default;
+--sleep 2
+set global server_audit_incl_users='odin, dva, tri';
+create table t1 (id int);
+set global server_audit_incl_users='odin, root, dva, tri';
+create table t2 (id int);
+set global server_audit_excl_users='odin, dva, tri';
+insert into t1 values (1), (2);
+select * from t1;
+set global server_audit_incl_users='odin, root, dva, tri';
+insert into t2 values (1), (2);
+select * from t2;
+alter table t1 rename renamed_t1;
+set global server_audit_events='connect,query';
+select 1,
+        2,
+        3;
+insert into t2 values (1), (2);
+select * from t2;
+--error ER_NO_SUCH_TABLE
+select * from t_doesnt_exist;
+--error 1064
+syntax_error_query;
+drop table renamed_t1, t2;
+show variables like 'server_audit%';
+set global server_audit_mode=1;
+set global server_audit_events='';
+create database sa_db;
+connect (con1,localhost,root,,test);
+connection con1;
+--sleep 2
+--sleep 2
+create table t1 (id2 int);
+insert into t1 values (1), (2);
+select * from t1;
+drop table t1;
+use sa_db;
+create table sa_t1(id int);
+insert into sa_t1 values (1), (2);
+drop table sa_t1;
+drop database sa_db;
+connection default;
+disconnect con1;
+--sleep 2
+--sleep 2
+create database sa_db;
+use sa_db;
+CREATE USER u1 IDENTIFIED BY 'pwd-123';
+GRANT ALL ON sa_db TO u2 IDENTIFIED BY "pwd-321";
+SET PASSWORD FOR u1 = PASSWORD('pwd 098');
+CREATE USER u3 IDENTIFIED BY '';
+drop user u1, u2, u3;
+
+set global server_audit_events='query_ddl';
+create table t1(id int);
+insert into t1 values (1), (2);
+select * from t1;
+select 2;
+(select 2);
+/*! select 2*/;
+/*comment*/ select 2;
+drop table t1;
+set global server_audit_events='query_ddl,query_dml';
+create table t1(id int);
+insert into t1 values (1), (2);
+select * from t1;
+select 2;
+drop table t1;
+set global server_audit_events='query_dml';
+create table t1(id int);
+insert into t1 values (1), (2);
+select * from t1;
+select 2;
+(select 2);
+/*! select 2*/;
+/*comment*/ select 2;
+drop table t1;
+set global server_audit_events='query_dcl';
+create table t1(id int);
+insert into t1 values (1), (2);
+select * from t1;
+CREATE USER u1 IDENTIFIED BY 'pwd-123';
+GRANT ALL ON sa_db TO u2 IDENTIFIED BY "pwd-321";
+SET PASSWORD FOR u1 = PASSWORD('pwd 098');
+--error 1064
+SET PASSWORD FOR u1=<secret>;
+CREATE USER u3 IDENTIFIED BY '';
+drop user u1, u2, u3;
+select 2;
+(select 2);
+/*! select 2*/;
+/*comment*/ select 2;
+drop table t1;
+set global server_audit_events='';
+
+set global server_audit_query_log_limit= 15;
+select (1), (2), (3), (4);
+select 'A', 'B', 'C', 'D';
+set global server_audit_query_log_limit= 1024;
+drop database sa_db;
+
+set global server_audit_file_path='.';
+--replace_regex /\.[\\\/]/HOME_DIR\//
+show status like 'server_audit_current_log';
+set global server_audit_file_path='';
+show status like 'server_audit_current_log';
+set global server_audit_file_path='  ';
+show status like 'server_audit_current_log';
+set global server_audit_file_path='nonexisting_dir/';
+show status like 'server_audit_current_log';
+show variables like 'server_audit%';
+uninstall plugin server_audit;
+
+let $MYSQLD_DATADIR= `SELECT @@datadir`;
+# replace the timestamp and the hostname with constant values
+--replace_regex /[0-9]* [0-9][0-9]:[0-9][0-9]:[0-9][0-9]\,[^,]*\,/TIME,HOSTNAME,/ /\,[1-9][0-9]*\,/,1,/ /\,[1-9][0-9]*/,ID/
+cat_file $MYSQLD_DATADIR/server_audit.log;
+remove_file $MYSQLD_DATADIR/server_audit.log;
+

sql/sql_connect.cc

@@ -1017,7 +1017,7 @@ bool setup_connection_thread_globals(THD *thd)
 bool login_connection(THD *thd)
 {
   NET *net= &thd->net;
-  int error;
+  int error= 0;
   DBUG_ENTER("login_connection");
   DBUG_PRINT("info", ("login_connection called by thread %lu",
                       thd->thread_id));
@@ -1036,7 +1036,8 @@ bool login_connection(THD *thd)
       my_sleep(1000);				/* must wait after eof() */
 #endif
     statistic_increment(aborted_connects,&LOCK_status);
-    DBUG_RETURN(1);
+    error=1;
+    goto exit;
   }
   /* Connect completed, set read/write timeouts back to default */
   my_net_set_read_timeout(net, thd->variables.net_read_timeout);
@@ -1046,10 +1047,13 @@ bool login_connection(THD *thd)
   if (increment_connection_count(thd, TRUE))
   {
     my_error(ER_OUTOFMEMORY, MYF(0), 2*sizeof(USER_STATS));
-    DBUG_RETURN(1);
+    error= 1;
+    goto exit;
   }
 
-  DBUG_RETURN(0);
+exit:
+  MYSQL_AUDIT_NOTIFY_CONNECTION_CONNECT(thd);
+  DBUG_RETURN(error);
 }
 
 
@@ -1187,7 +1191,6 @@ bool thd_prepare_connection(THD *thd)
   bool rc;
   lex_start(thd);
   rc= login_connection(thd);
-  MYSQL_AUDIT_NOTIFY_CONNECTION_CONNECT(thd);
   if (rc)
     return rc;