问题背景：
有两台mysql，一主一从，开发在代码里面连MySQL集群，发现有报错。连主库单点OK，连从库单点报错：
Table 'performance_schema.session_variables' doesn't exist
Could not create connection to database server. Attempted reconnect 3 times. Giving up.在数据库从库执行mysql> show global status like "%abort%";，报如下错误：
mysql> show global status like "%abort%";
ERROR 1146 (42S02): Table 'performance_schema.global_status' doesn't exist解决方法：
参考网上的解决文档，在mysql从库命令行执行命令：
sudo mysql_upgrade -u root -p –force执行结果如下：
[root@slave-2 mysql]# mysql_upgrade -u root -p –force
Enter password: #这里输入数据库root用户的密码
Checking if update is needed.
Checking server version.
Running queries to upgrade MySQL server.
Checking system database.
mysql.columns_priv OK
mysql.db OK
mysql.engine_cost OK
mysql.event OK
mysql.func OK
mysql.general_log OK
mysql.gtid_executed OK
mysql.help_category OK
mysql.help_keyword OK
mysql.help_relation OK
mysql.help_topic OK
mysql.innodb_index_stats OK
mysql.innodb_table_stats OK
mysql.ndb_binlog_index OK
mysql.plugin OK
mysql.proc OK
mysql.procs_priv OK
mysql.proxies_priv OK
mysql.server_cost OK
mysql.servers OK
mysql.slave_master_info OK
mysql.slave_relay_log_info OK
mysql.slave_worker_info OK
mysql.slow_log OK
mysql.tables_priv OK
mysql.time_zone OK
mysql.time_zone_leap_second OK
mysql.time_zone_name OK
mysql.time_zone_transition OK
mysql.time_zone_transition_type OK
mysql.user OK
Upgrading the sys schema.
Checking databases.
ApolloConfigDB.App OK
ApolloConfigDB.AppNamespace OK
ApolloConfigDB.Audit OK
#中间省略若干业务库和表
locman.process_node_person OK
locman.process_type_base OK
monitor.dubbo_invoke OK
operations.app_install OK
operations.app_install_status OK
operations.auth_group OK
operations.auth_group_permissions OK
operations.auth_permission OK
operations.auth_user OK
operations.auth_user_groups OK
operations.auth_user_user_permissions OK
operations.business_admin OK
operations.celery_taskmeta OK
operations.celery_tasksetmeta OK
operations.cluster OK
operations.django_admin_log OK
operations.django_content_type OK
operations.django_migrations OK
operations.django_session OK
operations.djcelery_crontabschedule OK
operations.djcelery_intervalschedule OK
operations.djcelery_periodictask OK
operations.djcelery_periodictasks OK
operations.djcelery_taskstate OK
operations.djcelery_workerstate OK
operations.host_ps OK
operations.jenkins_jobs OK
operations.module OK
operations.operation_log OK
operations.project_center OK
operations.project_center_deploy_salt_minion OK
operations.project_deploy_info OK
operations.project_docker_info OK
operations.project_image_save OK
operations.receiver_hooks OK
operations.salt_master OK
operations.salt_minion OK
operations.salt_minion_module OK
sys.sys_config OK
Upgrade process completed successfully.
Checking if update is needed.然后再重启数据库从库：
[root@slave-2 ~]# systemctl restart mysqld然后开发再用代码重新连MySQL，就可以正常连了。从库执行show global status like "%abort%";也没有报错了
mysql> show global status like "%abort%";
+------------------+-------+
| Variable_name | Value |
+------------------+-------+
| Aborted_clients | 1 |
| Aborted_connects | 0 |
+------------------+-------+
2 rows in set (0.00 sec)
mysql> 然后从库检查主从复制情况，一切正常
参考文档：
https://stackoverflow.com/questions/31967527/table-performance-schema-session-variables-doesnt-exist