The salve replication thread stops, and an error 1872 is reported when trying to start slave

mysql> system perror 1872  
MySQL error code 1872 (ER_SLAVE_RLI_INIT_REPOSITORY): Slave failed to initialize relay log info structure from the repository

Solution process
1. It seems that the warehouse of relay log cannot be found, but the location of relay log is set

mysql> show variables like 'relay%';
+---------------------------+---------------------------------------------------+
| Variable_name             | Value                                             |
+---------------------------+---------------------------------------------------+
| relay_log                 | relay-log                                         |
| relay_log_basename        | /datadir/relay-log       |
| relay_log_index           | /datadir/relay-log.index |
| relay_log_info_file       | relay-log.info

2. Log related information is also recorded in master.infor, and no exception is found after viewing
3. Reset the replication information

mysql> reset master;
Query OK, 0 rows affected (0.00 sec)
mysql> show slave status\G
**************************\* 1. row ***************************
               Slave_IO_State: 
                  Master_Host: *******
                  Master_User: repl
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: 
          Read_Master_Log_Pos: 4
               Relay_Log_File: relay-log.000001
                Relay_Log_Pos: 4

Note: There is still a copy message

After that, proceed to
set global gtid_purged=’*******’;
change master to …… ;
The error is still reported when starting the slave
4. MySQL DOC description of start slave:
RESET SLAVE does not change any replication connection parameters such as master host, master port, master user, or master password, which are retained in memory. This means that START SLAVE can be issued without requiring a CHANGE MASTER TO statement following RESET SLAVE.

Connection parameters are reset by RESET SLAVE ALL.

5. Use reset slave all to clear all replication information, then reset gtid_purged and master.infor
After start slave, replication is normal