Flushing engine logs when switching from primary to secondary

Summary:
We need to make sure that we flush the engine logs (aka sync the engines)
before we switch from binlog to apply log (i.e. switch from primary to
secondary) to recover correctly in host restart case. Otherwise if host
restarts after apply log has been created and the engine goes back in
time on recovery, we'll use the apply log for recovery and assume that
engine is caught up.

Differential Revision: D50385170

Author: abhinav04sharma

sql/binlog.cc

@@ -12372,6 +12372,10 @@ int binlog_change_to_apply() {
     DBUG_RETURN(0);
   }
 
+  if (ha_flush_logs()) {
+    DBUG_RETURN(1);
+  }
+
   int error = 0;
   LOG_INFO linfo;
   mysql_mutex_lock(mysql_bin_log.get_log_lock());
@@ -12456,7 +12460,9 @@ int binlog_change_to_binlog(THD *thd) {
   // batch of transactions. This is important because the act of switching trx
   // logs from "apply-logs-*" to "binary-logs-*" looks like a rotation to other
   // parts of the system and rotation is always a 'sync' point
-  ha_flush_logs(NULL);
+  if (ha_flush_logs()) {
+    DBUG_RETURN(1);
+  }
 
   mysql_mutex_lock(mysql_bin_log.get_log_lock());
   const bool is_locked = dump_log.lock();