mysql collector: slave_status charts per replication channel

[ilyam8]

Summary

Fixes: #6353

Ref: https://dev.mysql.com/doc/refman/8.0/en/replication-channels.html

To provide compatibility with previous versions, the MySQL server automatically creates on startup a default channel whose name is the empty string (""). This channel is always present; it cannot be created or destroyed by the user. If no other channels (having nonempty names) have been created, replication statements act on the default channel only, so that all replication statements from older slaves function as expected

SHOW SLAVE STATUS reports the status for all channels, except the group_replication_applier channel.

---

As we can see in #6353 (comment)

SHOW SLAVE STATUS returns several rows, one row per replication channel.

Before this PR:

• slave status charts only for the first channel.

After this PR:

• slave status charts for every channel.

Component Name

/collectors/python.d.plugin/mysql

Additional Information

Tests:

• i tested PR with 1 replication channel, works ok
• i didnt test the PR with n replication channels (@vpapas will do i hope)

@vpapas could you test the PR?

---

SHOW SLAVE STATUS reports the status for all channels, except the group_replication_applier channel.

From what i understand the only way to monitor replication metrics if instance in replication group is to execute SHOW SLAVE STATUS CHANNEL <NAME> for every channel. SHOW SLAVE STATUS returns nothing in that case.

[ilyam8]

ok, i tested the PR, it works ok if show slave status returns several rows and there is Channel_Name in the row.

show slave status

mysql> show slave status\G
*************************** 1. row ***************************
Slave_IO_State:
Master_Host: xxxxxxxxxxx
Master_User: user
Master_Port: 3306
Connect_Retry: 60
Master_Log_File:
Read_Master_Log_Pos: 4
Relay_Log_File: xxxxx@[email protected]
Relay_Log_Pos: 4
Relay_Master_Log_File:
Slave_IO_Running: No
Slave_SQL_Running: No
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 0
Relay_Log_Space: 154
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: NULL
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: 0
Master_UUID:
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
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: 64485c6f-334c-11e8-b1d8-0050569d2e3c:1-19159184
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name: channel01
Master_TLS_Version:
*************************** 2. row ***************************
Slave_IO_State:
Master_Host: xxxxxxxxxxx
Master_User: user
Master_Port: 3306
Connect_Retry: 60
Master_Log_File:
Read_Master_Log_Pos: 4
Relay_Log_File: xxxx@[email protected]
Relay_Log_Pos: 4
Relay_Master_Log_File:
Slave_IO_Running: No
Slave_SQL_Running: No
Replicate_Do_DB:
Replicate_Ignore_DB:
Replicate_Do_Table:
Replicate_Ignore_Table:
Replicate_Wild_Do_Table:
Replicate_Wild_Ignore_Table:
Last_Errno: 0
Last_Error:
Skip_Counter: 0
Exec_Master_Log_Pos: 0
Relay_Log_Space: 154
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: NULL
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: 0
Master_UUID:
Master_Info_File: mysql.slave_master_info
SQL_Delay: 0
SQL_Remaining_Delay: NULL
Slave_SQL_Running_State:
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: 64485c6f-334c-11e8-b1d8-0050569d2e3c:1-19159184
Auto_Position: 1
Replicate_Rewrite_DB:
Channel_Name: channel02
Master_TLS_Version:
2 rows in set (0.00 sec)