Adjust the distribution of replicas

This topic describes how to modify the locality of a tenant in a cluster to adjust the distribution of log stream replicas in the tenant.

For more information about how to modify the locality, see Modify locality.

Prerequisites

Before you modify the locality of a tenant, verify the resource information of each node in the target zone. If OBServer nodes in the target zone do not have sufficient resources to accommodate the new resource units of the tenant, the locality cannot be changed.

For more information about how to view the resource information of each node in a zone, see View tenant and resource information.

Considerations

• The locality of the tenant must be specified.

• When the locality of a tenant changes, the distribution of table replicas in the tenant also changes.

• Before you change the locality of a tenant, make sure that the previous locality change is completed.

• You can perform only one action at a time when you modify the locality. For example, if you want to replace zone3 with zone4, you must add zone4 and then remove zone3.

• After you add a replica to a tenant, the locality of the tenant does not match the primary zone setting of the tenant. If the new zone is involved in leader switchover, you must modify the primary zone setting. If the new zone is not involved in leader switchover, you do not need to modify the primary zone setting.

Procedure

The following example describes how to modify the locality of the mysql001 tenant from FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 to FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4.

1. Log in to the sys tenant of the cluster as the root user.

   obclient -h172.30.xxx.xxx -P2883 -uroot@sys#obdemo -pxxxx -A
   

2. Access the database named oceanbase.

   obclient>use oceanbase; 
   

3. Query the locality of the mysql001 tenant.

   obclient> SELECT TENANT_ID,TENANT_NAME,TENANT_TYPE,PRIMARY_ZONE,LOCALITY FROM oceanbase.DBA_OB_TENANTS;
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   | TENANT_ID | TENANT_NAME | TENANT_TYPE | PRIMARY_ZONE      | LOCALITY                                    |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   |         1 | sys         | SYS         | zone1;zone2;zone3 | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 |
   |      1001 | META$1002   | META        | zone1;zone2;zone3 | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 |
   |      1002 | mysql001    | USER        | zone1;zone2;zone3 | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   

   The query result shows that the mysql001 tenant has a full-featured replica in each of zone 1, zone 2, and zone 3.

4. Modify the locality of the mysql001 tenant to add a replica in zone 4.

   obclient>ALTER TENANT mysql001 locality="FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3, FULL{1}@zone4";
   

5. Query the execution status of the locality modification job.

    obclient>SELECT * FROM oceanbase.DBA_OB_TENANT_JOBS WHERE JOB_TYPE = 'ALTER_TENANT_LOCALITY';
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
    | JOB_ID | JOB_TYPE              | JOB_STATUS | RESULT_CODE | PROGRESS | START_TIME                 | MODIFY_TIME                | TENANT_ID | SQL_TEXT                                                                     | EXTRA_INFO                                  | RS_SVR_IP      | RS_SVR_PORT |
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
    |      1 | ALTER_TENANT_LOCALITY | SUCCESS    |        NULL |        0 | 2023-01-05 19:38:38.416011 | 2023-01-05 19:38:38.416011 |      1002 | ALTER TENANT mysql001 locality='FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3, FULL{1}@zone4' | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 | xx.xx.xx.237 |        2882 |
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
   

   If the value of JOB_STATUS is SUCCESS, the locality modification job is successful.

6. Modify the locality of the mysql001 tenant to remove the replica in zone 3.

   obclient>ALTER TENANT mysql001 locality="FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4";
   

7. Query the execution status of the locality modification job.

    obclient>SELECT * FROM oceanbase.DBA_OB_TENANT_JOBS WHERE JOB_TYPE = 'ALTER_TENANT_LOCALITY';
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
    | JOB_ID | JOB_TYPE              | JOB_STATUS | RESULT_CODE | PROGRESS | START_TIME                 | MODIFY_TIME                | TENANT_ID | SQL_TEXT                                                                     | EXTRA_INFO                                  | RS_SVR_IP      | RS_SVR_PORT |
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
    |      1 | ALTER_TENANT_LOCALITY | SUCCESS    |        NULL |        0 | 2023-01-05 19:38:38.416011 | 2023-01-05 19:38:38.416011 |      1002 | ALTER TENANT mysql001 locality='FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4' | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3, FULL{1}@zone4 | xx.xx.xx.237 |        2882 |
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
   

   If the value of JOB_STATUS is SUCCESS, the locality modification job is successful.

8. Query the modified locality of the mysql001 tenant.

   obclient> SELECT TENANT_ID,TENANT_NAME,TENANT_TYPE,PRIMARY_ZONE,LOCALITY FROM oceanbase.DBA_OB_TENANTS;
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   | TENANT_ID | TENANT_NAME | TENANT_TYPE | PRIMARY_ZONE      | LOCALITY                                    |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   |         1 | sys         | SYS         | zone1;zone2;zone3 | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 |
   |      1001 | META$1002   | META        | zone1;zone2       | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4 |
   |      1002 | mysql001    | USER        | zone1;zone2       | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4 |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   

The query results in step 3 and step 8 show that the locality of the mysql001 tenant is changed from FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 to FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone4, and the mysql001 tenant has a full-featured replica in each of zone1, zone2, and zone4.

After you add a replica to a tenant, the locality of the tenant does not match the primary zone setting of the tenant. If the new zone is involved in leader switchover, you must modify the primary zone setting. For more information about how to modify the primary zone setting, see Modify the primary zone setting. If the new zone is not involved in leader switchover, you do not need to modify the primary zone setting.

References

• Locality

• Modify locality

• View locality

• Add replicas

• Remove replicas

• Modify the primary zone setting