MDEV-20215: binlog.show_concurrent_rotate failed in buildbot with wrong result10.4-MDEV-20215

Problem:
=======
A race condition exists between two connections to
get the binary logs lock, where the first connection
tries to SHOW BINARY LOGS and uses the lock to
obtain all logs, and the second connection uses the
lock in RESET MASTER to purge the logs and restart
the rotation.

Solution:
=======
Where it is expected to have some amount of stale data
in the SHOW BINARY LOGS call, limit it to only the most
current binary log file size. More specifically, after going
through the cached file list (which can take up to 20
seconds), check to see if any new files have been created
in the directory. If so, analyze each new created file.
Additionally, the check for purged files only checks file
name, so to enhance the logic here, additionally
consider timestamp to reduce wasted time on file stats.

1 files changed, 3 insertions, 0 deletions

diff --git a/sql/sql_reload.cc b/sql/sql_reload.cc
index 76fb9819fd5..d57db51a5f6 100644
--- a/sql/sql_reload.cc
+++ b/sql/sql_reload.cc
@@ -150,6 +150,9 @@ bool reload_acl_and_cache(THD *thd, unsigned long long options,
       DYNAMIC_ARRAY *drop_gtid_domain=
         (thd && (thd->lex->delete_gtid_domain.elements > 0)) ?
         &thd->lex->delete_gtid_domain : NULL;
+
+      DEBUG_SYNC(thd, "at_flush_pre_rotate_and_purge");
+
       if (mysql_bin_log.rotate_and_purge(true, drop_gtid_domain))
         *write_to_binlog= -1;