How to implement MySQL bidirectional backup

[mysqld]
# Server unique identifier server-id=1
# Binary log file name log-bin=mysql-bin

# Databases that need to be backed up, multiple databases are separated by , binlog-do-db=piumnl
# Databases that need to be replicated, multiple databases are separated by replicate-do-db=piumnl
# Relay log file name relay_log=mysqld-relay-bin
# Manually start the synchronization service to avoid data log asynchronization caused by sudden downtime skip-slave-start=ON
# For mutual master-slave, you need to add this line log-slave-updates=ON
# Disable symbolic links to prevent security risks. You don't need to add symbolic-links=0

# Optional# resolve - [Warning] Slave SQL: If a crash happens this configuration does not guarantee that the relay log info will be consistent, Error_code: 0
master-info-repository=table
relay-log-info-repository=table
relay-log-recovery=1

#Optional# Disabling DNS resolution will invalidate the domain name used during authorization skip-host-cache
skip-name-resolve

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

# No longer explain each configuration item [mysqld]
server-id=2
log-bin=mysql-bin

binlog-do-db=piumnl
replicate-do-db=piumnl
relay_log=mysql-relay-bin
skip-slave-start=ON
log-slave-updates=ON
symbolic-links=0

# resolve - [Warning] Slave SQL: If a crash happens this configuration does not guarantee that the relay log info will be consistent, Error_code: 0
master-info-repository=table
relay-log-info-repository=table
relay-log-recovery=1

skip-host-cache
skip-name-resolve

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES

create user 'rep'@'%' identified by 'rep'; # Create an account grant replication slave on *.* to 'rep'@'%'; # Grant the account master-slave backup permissions for any table in any database

show master status\G;
# Here you need to pay attention to the File and Position values

# master_log_file is the File value of the first step operation # master_log_pos is the Position value of the first step operation change master to master_host=<master_hostname>, master_user=<rep_username>, master_port=<master_port>, master_password=<rep_password>, master_log_file='mysql-log.000003', master_log_pos=154;
start slave;

show slave status\G;
# Check the two most important items. Both must be Yes. If one is No, check the error log file to see where the problem is. # Slave_IO_Running: Yes
# Slave_SQL_Running: Yes

stop slave;
flush logs;
start slave;

# Perform the following operations to reset # If the binary log or relay log has other functions, do not perform the following operations reset master;
reset slave;
flush logs;