Add replicas

This topic describes how to add log stream replicas to a tenant in a cluster by modifying the locality of the tenant.

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

Prerequisites

Before you add a replica, check whether the tenant has a resource pool in the target zone. If not, modify the zone list of the existing resource pool of the tenant or add a resource pool to the tenant. When you add a resource pool, the number of units in the resource pool must be the same as that in the existing resource pool of the tenant. For more information, see Modify attributes of a resource pool or Create a resource pool.

You must also check 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.

• When a tenant locality modification is not finished, the next tenant locality modification cannot be performed.

• 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 first and then remove zone3.

• We recommend that you modify the primary zone before you modify the locality.

  Here are some examples:

  1. Assume that zone3 is a primary zone with the highest priority. When you remove zone3, read and write services of the tenant are affected during locality modification.

  2. Assume that the primary zone is set to RANDOM when you add zone4. After zone4 is added, it also provides read and write services.

Procedure

The following example describes how to modify the locality of tenant mysql001 from FULL{1}@zone1, FULL{1}@zone2 to FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3, and add a replica to the tenant in zone3.

1. Log on 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. View 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       | FULL{1}@zone1, FULL{1}@zone2                |
   |      1002 | mysql001    | USER        | zone1;zone2       | FULL{1}@zone1, FULL{1}@zone2                |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   

   The query result shows that the mysql001 tenant has a full-featured replica in both zone1 and zone2.

4. Modify the locality of the mysql001 tenant.

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

5. View the execution status of the locality change 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}@zone1, FULL{1}@zone2                | xx.xx.xx.237 |        2882 |
    +--------+-----------------------+------------+-------------+----------+----------------------------+----------------------------+-----------+------------------------------------------------------------------------------+---------------------------------------------+----------------+-------------+
   

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

6. View 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}@zone3 |
   |      1002 | mysql001    | USER        | zone1;zone2       | FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3 |
   +-----------+-------------+-------------+-------------------+---------------------------------------------+
   

The query results in step 3 and step 6 show that the locality of the mysql001 tenant is changed from FULL{1}@zone1, FULL{1}@zone2 to FULL{1}@zone1, FULL{1}@zone2, FULL{1}@zone3, and the mysql001 tenant has a full-featured replica in each of zone1, zone2, and zone3.

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

References

• Locality

• Modify locality

• View locality

• Remove replicas