xtrabackup --slave-info does not handle multi-master replication

[Johan Nilsson]

When running Percona Xtrabackup 2.4.1, the option --slave-info does not include channel name.
And as far as I can understand when reviewing the code, multiple channels will not work correctly...

# xtrabackup --version
xtrabackup version 2.4.1 based on MySQL server 5.7.10 Linux (x86_64) (revision id: a2dc9d4)

# mysql -e "select @@version
+------------+
| @@version |
+------------+
| 5.7.11-log |
+------------+
# mysql -e "show slave status\G"
*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: <host>
                  Master_User: <user>
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: mysql-bin.000003
          Read_Master_Log_Pos: 151
               Relay_Log_File: mysql-relay-<host>.000011
                Relay_Log_Pos: 364
        Relay_Master_Log_File: mysql-bin.000003
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB:
           Replicate_Do_Table:
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table:
  Replicate_Wild_Ignore_Table: mysql.%
                   Last_Errno: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 151
              Relay_Log_Space: 747
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 972
                  Master_UUID: 7095dd7c-d634-11e5-8252-6cae8b52a7ba
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 86400
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set:
            Executed_Gtid_Set:
                Auto_Position: 0
         Replicate_Rewrite_DB:
                 Channel_Name: <channel>
           Master_TLS_Version:

# cat xtrabackup_slave_info
CHANGE MASTER TO MASTER_LOG_FILE='mysql-bin.000003', MASTER_LOG_POS=151

Looking at storage/innobase/xtrabackup/innobackupex, it seems like the info for xtrabackup_slave_info is fetched from 'SHOW SLAVE STATUS', when I guess that the correct way should be to select information from mysql.slave_master_info, mysql.slave_relay_log_info and mysql.gtid_executed.
An alternative solution whould be to get configured channel names from mysql.slave_master_info, and then do 'SHOW SLAVE STATUS FOR CHANNEL $channel_name'

[Sergei Glushchenko (sergei.glushchenko)]

Thank you for the bug report

[Vasily Nemkov (vasily.nemkov)]

PR: https://github.com/percona/percona-xtrabackup/pull/362

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXB-1022