Gtid_log_event thread_id missing in binlog when pseudo_thread_id is set to 0 or negative

If pseudo_thread_id is set to 0 (or implicitly set to 0 because
it was attempted to be set to a negative value), then the
thread_id attribute of the Gtid_log_event will not be written
at all, whereas the Query_log_event still will write
thread_id=0.  The underlying problem was that the
FL_EXTRA_THREAD_ID would only be added if thread_id was greater
than 0.

This patch fixes this by changing the condition to mark the
FL_EXTRA_THREAD_ID when generating a GTID log event, such that
it will always be written on the primary, and if on the slave,
the rpl_group_info's gtid_ev_flags_extra is checked to see if
the flag was present when reading it in.

Reviewed By:
============
Andrei Elkin <andrei.elkin@mariadb.com>

mysql-test/suite/rpl/r/rpl_gtid_thread_id.result

@@ -43,6 +43,18 @@ include/stop_slave.inc
 SET @@GLOBAL.slave_parallel_threads=0;
 include/start_slave.inc
 #
+# MDEV-33924: If psuedo_thread_id is set to 0, this should still be
+# written and propagated to slaves
+connection master;
+set @@pseudo_thread_id=0;
+insert into t1 values(33924);
+# MYSQL_BINLOG local > primary_outfile
+include/assert_grep.inc [GTID event's thread_id should write pseudo_thread_id value of 0]
+connection slave;
+connection slave;
+# MYSQL_BINLOG local > replica_outfile
+include/assert_grep.inc [A 0 value for GTID event's thread_id should be propagated on replicas]
+#
 # Cleanup
 connection master;
 drop table t1;

mysql-test/suite/rpl/t/rpl_gtid_thread_id.test

@@ -116,6 +116,43 @@ insert into t1 values(4);
 --source include/start_slave.inc
 
 
+--echo #
+--echo # MDEV-33924: If psuedo_thread_id is set to 0, this should still be
+--echo # written and propagated to slaves
+--connection master
+--let datadir= `select @@datadir`
+--let filename= query_get_value(SHOW MASTER STATUS, File, 1)
+--let local=$datadir/$filename
+--let $old_pseudo_id= `SELECT @@SESSION.pseudo_thread_id`
+set @@pseudo_thread_id=0;
+insert into t1 values(33924);
+--echo # MYSQL_BINLOG local > primary_outfile
+--exec $MYSQL_BINLOG $local > $primary_outfile
+
+--let $assert_count= 1
+--let $assert_text= GTID event's thread_id should write pseudo_thread_id value of 0
+--let $assert_select=GTID [0-9]-[0-9]-[0-9].*thread_id=0\$
+--let $assert_file= $primary_outfile
+--source include/assert_grep.inc
+
+--sync_slave_with_master
+--connection slave
+--let datadir= `select @@datadir`
+--let filename= query_get_value(SHOW MASTER STATUS, File, 1)
+--let local=$datadir/$filename
+--echo # MYSQL_BINLOG local > replica_outfile
+--exec $MYSQL_BINLOG $local > $replica_outfile
+
+--let $assert_text= A 0 value for GTID event's thread_id should be propagated on replicas
+--let $assert_select=GTID [0-9]-[0-9]-[0-9].*thread_id=0\$
+--let $assert_file= $replica_outfile
+--source include/assert_grep.inc
+
+--disable_query_log
+--connection master
+--eval set @@pseudo_thread_id=$old_pseudo_id
+--enable_query_log
+
 
 --echo #
 --echo # Cleanup

sql/log_event.cc

@@ -2462,8 +2462,6 @@ Gtid_log_event::Gtid_log_event(const uchar *buf, uint event_len,
     {
       thread_id= uint8korr(buf);
       buf+= 8;
-
-      DBUG_ASSERT(thread_id > 0);
     }
   }
   /*

sql/log_event_server.cc

@@ -2841,7 +2841,8 @@ Gtid_log_event::Gtid_log_event(THD *thd_arg, uint64 seq_no_arg,
   /* Preserve any DDL or WAITED flag in the slave's binlog. */
   if (thd_arg->rgi_slave)
     flags2|= (thd_arg->rgi_slave->gtid_ev_flags2 & (FL_DDL|FL_WAITED));
-  if (thread_id > 0)
+  if (!thd->rgi_slave ||
+      thd_arg->rgi_slave->gtid_ev_flags_extra & FL_EXTRA_THREAD_ID)
     flags_extra|= FL_EXTRA_THREAD_ID;
 
   XID_STATE &xid_state= thd->transaction->xid_state;