Scale out or scale in tenant resources

You can scale out or scale in tenant resources by adjusting the UNIT_NUM parameter of resource pools. This allows you to dynamically change the number of units available to the tenant in each zone, thereby increasing or decreasing the tenant's service capacity in the corresponding zone.

OceanBase Database supports both homogeneous and heterogeneous zone modes for tenants:

• In homogeneous zone mode, all zones of the tenant must have the same UNIT_NUM.

• In heterogeneous zone mode, the UNIT_NUM can vary across zones, but a tenant can have at most two different UNIT_NUM values across all zones.

Changing the UNIT_NUM parameter can be categorized into two types: increasing and decreasing the value.

• For tenants in homogeneous zone mode:

  • If the resource pool is not granted to the tenant, you can independently increase or decrease the UNIT_NUM of the resource pool.

  • If the resource pool is granted to the tenant, you can only adjust the UNIT_NUM of all granted resource pools simultaneously, not individually.

• For tenants in heterogeneous zone mode, you can adjust the UNIT_NUM of resource pools whether or not they are granted to the tenant. This means you can either adjust the UNIT_NUM of all granted resource pools simultaneously or independently adjust the UNIT_NUM of individual resource pools.

Increasing or decreasing the UNIT_NUM essentially involves adding or removing units. Here are some example statements for adjusting the UNIT_NUM of a resource pool:

1. For a resource pool in heterogeneous zone mode, or for an ungranted resource pool in homogeneous zone mode, you can independently adjust the UNIT_NUM of the resource pool.

   Assume the following resource pool information:

   obclient> CREATE RESOURCE POOL rp1 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2');
   

   Here are some adjustment examples:

   obclient> ALTER RESOURCE POOL rp1 UNIT_NUM 3; // Increase UNIT_NUM
   

   obclient> ALTER RESOURCE POOL rp1 UNIT_NUM 2; // Decrease UNIT_NUM
   

   obclient> ALTER RESOURCE POOL rp1 UNIT_NUM 1 DELETE UNIT = (1001, 1003); // Specify units to decrease UNIT_NUM
   

2. Adjust the UNIT_NUM of all resource pools for the tenant simultaneously.

   Assume the following resource pool information for the tenant:

   obclient> CREATE RESOURCE POOL rp2 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2');
   

   obclient> CREATE RESOURCE POOL rp3 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone3');
   

   obclient> CREATE TENANT tt RESOURCE_POOL_LIST = ('rp2', 'rp3');
   

   Here are some adjustment examples:

   obclient> ALTER RESOURCE TENANT tt UNIT_NUM = 3; // Increase UNIT_NUM for both resource pools
   

   obclient> ALTER RESOURCE TENANT tt UNIT_NUM = 1; // Decrease UNIT_NUM for both resource pools
   

Increase UNIT_NUM

• Example 1: Increase UNIT_NUM for a single resource pool

  After you create a resource pool, you can increase the UNIT_NUM of a single resource pool.

  Assume that the information of the resource pool to be adjusted is as follows:

  obclient> CREATE RESOURCE POOL r_p0 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2', 'zone3');
  

  For a resource pool in a heterogeneous zone mode or a resource pool not granted to a tenant in a homogeneous zone mode, you can increase the UNIT_NUM of the resource pool by using the following statement:

  obclient> ALTER RESOURCE POOL r_p0 UNIT_NUM 3;
  

• Example 2: Increase UNIT_NUM for a tenant

  Usually, you increase the UNIT_NUM of a tenant when you scale out the tenant. For example, for a resource pool granted to a tenant:

  obclient> CREATE RESOURCE POOL r_p0 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2', 'zone3');
  

  obclient> CREATE TENANT tt RESOURCE_POOL_LIST = ('r_p0');
  

  In the preceding example, the tenant tt uses the resource pool r_p0. Each zone (zone1, zone2, and zone3) has 2 units. As the business volume increases, the 2 units in each zone cannot meet the business requirements. Therefore, you need to increase the UNIT_NUM to improve the service capability of the tenant to meet the new business requirements.

  You can execute the following statement to increase the number of units of the tenant in the resource pool r_p0 to 3 to improve the service capability of the tenant.

  obclient> ALTER RESOURCE TENANT tt UNIT_NUM = 3;
  

Decrease UNIT_NUM

• Example 1: Decrease UNIT_NUM for a single resource pool

  After you create a resource pool, you can decrease the UNIT_NUM of a single resource pool. Assume that the information of the resource pool to be adjusted is as follows.

  obclient> CREATE RESOURCE POOL r_p0 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2', 'zone3');
  

  For a resource pool in a heterogeneous zone mode or a resource pool not granted to a tenant in a homogeneous zone mode, you can decrease the UNIT_NUM of the resource pool by using the following statement:

  obclient> ALTER RESOURCE POOL r_p0 UNIT_NUM 1;
  

  You can also decrease the UNIT_NUM of a single resource pool by deleting specified units. The statement is as follows:

  obclient> ALTER RESOURCE POOL r_p0 UNIT_NUM 1 DELETE UNIT=(1001,1002,1003);
  

• Example 2: Decrease UNIT_NUM for a tenant

  Usually, you decrease the UNIT_NUM of a tenant when you scale in the tenant. For example, for a resource pool granted to a tenant:

  obclient> CREATE RESOURCE POOL r_p0 UNIT 'uc1', UNIT_NUM 2, ZONE_LIST ('zone1', 'zone2', 'zone3');
  

  obclient> CREATE TENANT tt RESOURCE_POOL_LIST = ('r_p0');
  

  In the preceding example, the tenant tt uses the resource pool r_p0. Each zone (zone1, zone2, and zone3) has 2 units. As the business requirements change, the 2 units in each zone are no longer needed. Therefore, you need to decrease the UNIT_NUM to meet the new business requirements.

  You can execute the following statement to decrease the number of units of the tenant in the resource pool r_p0 to 1 to reduce the service capability of the tenant.

  obclient> ALTER RESOURCE TENANT tt UNIT_NUM = 1;
  

  In a homogeneous zone mode, you can also decrease the UNIT_NUM by deleting specified UNIT_GROUP.

  obclient> ALTER RESOURCE TENANT tt  UNIT_NUM = 1 DELETE UNIT_GROUP =(1001);
  

References

• View tenant and resource information

• Scale in and out a tenant by adjusting the unit number