Configure global CPU resource isolation for foreground and background tasks

OceanBase Database supports global CPU resource isolation for foreground and background tasks in all tenants.

Overview

In a high-performance computing environment, reasonable resource allocation and isolation are decisive in ensuring system stability and improving efficiency. An effective resource isolation strategy can prevent resource contention and interference between tasks, thereby improving the resource utilization efficiency and overall service quality. At present, OceanBase Database allows you to configure different unit configs for tenants to implement resource isolation between the tenants, and use the DBMS_RESOURCE_MANAGER system package to configure resource isolation within a tenant.

Before you enable global CPU resource isolation for foreground and background tasks on an OBServer node, the OBServer node supports CPU resource isolation between tenants and within a tenant, as shown in the following figure:

The isolation hierarchy is shown as a tree structure. The strategies of resource isolation between tenants depend on the unit configs of the tenants. The strategies of resource isolation between tasks within a tenant are determined by the DBMS_RESOURCE_MANAGER system package.

After you enable global CPU resource isolation for foreground and background tasks, the system creates a tenant-level sub-control group (cgroup) based on background tasks. The background sub-cgroup can be understood as a virtual tenant. The MAX_CPU value of the virtual tenant is the same as the value of the global_background_cpu_quota parameter, and the MIN_CPU value of the virtual tenant is 1. The following figure shows the isolation hierarchy after global CPU resource isolation is enabled for foreground and background tasks.

After you enable global CPU resource isolation for foreground and background tasks, the maximum CPU resources available to all background tasks are limited by the global_background_cpu_quota parameter even if you do not specify strategies of resource isolation within a tenant. This prevents background tasks from affecting foreground tasks.

Scenarios

We recommend that you enable global CPU resource isolation for foreground and background tasks in the following scenarios:

• You expect global resource isolation for background tasks to prevent them from affecting foreground tasks.

• You want to avoid calculation or configuration of complex strategies of resource isolation between tenants and within a tenant, especially when a large number of tenants are deployed.

Prerequisites

You have configured the cgroup directory and enabled the cgroup feature on the OBServer node. For more information, see Configure cgroups.

Considerations

• CPU resources can be isolated between tenants. After you enable global CPU resource isolation for foreground and background tasks, the maximum CPU resources available to background tasks of each tenant are limited by the global_background_cpu_quota parameter and are equal to min(MAX_CPU of the tenant, global_background_cpu_quota).

  Notice

  In OceanBase Database V4.2.1 and later, CPU resources for the `sys` tenant are not limited, to avoid impact on requests from the `sys` tenant.

• CPU resources can be isolated within a tenant. After you enable global CPU resource isolation for foreground and background tasks, you can use the DBMS_RESOURCE_MANAGER system package to configure resource isolation within a tenant. The maximum CPU resources available to each background task of the tenant are calculated based on the maximum CPU resources available to all background tasks of the tenant and are equal to min(global_background_cpu_quota, MAX_CPU of the tenant) * UTILIZATION_LIMIT within the resource group.

Enable global CPU resource isolation for foreground and background tasks

In OceanBase Database, global CPU resource isolation for foreground and background tasks is controlled by the following two parameters:

• enable_global_background_resource_isolation

  This parameter specifies whether to enable global CPU resource isolation for foreground and background tasks. It is a cluster-level parameter. The default value is False, which specifies to disable global CPU resource isolation for foreground and background tasks. In this case, CPU resources for foreground and background tasks are isolated within a tenant. The setting takes effect only after you restart the OBServer node.

  The value True specifies to enable global CPU resource isolation for foreground and background tasks. In this case, CPU resources for background tasks are limited independently of tenants.

  For more information about the enable_global_background_resource_isolation parameter, see enable_global_background_resource_isolation.

• global_background_cpu_quota

  This parameter specifies the CPU quota available to background tasks. It is a cluster-level parameter. The default value is -1, which specifies that the CPU resources available to background tasks are limited by the cgroup.

  For more information about the global_background_cpu_quota parameter, see global_background_cpu_quota.

To enable global CPU resource isolation for foreground and background tasks, perform the following steps:

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

2. Execute the following statement to enable global CPU resource isolation for foreground and background tasks.

   obclient> ALTER SYSTEM SET enable_global_background_resource_isolation = True;
   

3. Specify the CPU quota available to background tasks based on your business needs.

   The value must be less than the CPU quota available to the current OBServer node.

   obclient> ALTER SYSTEM SET global_background_cpu_quota = 3;
   

4. Restart the OBServer node for the setting to take effect.

   After the setting takes effect, the system creates a background directory at the same level as all tenants in the original cgroup directory structure. The background directory acts as a cgroup directory for background tasks. The system also creates cgroup directories corresponding to all tenants in the background directory.

What to do next

Global CPU resource isolation for foreground and background tasks limits the CPU resources for background tasks from a global perspective. If you expect finer-grained resource isolation for background tasks, you can use the DBMS_RESOURCE_MANAGER system package to configure resource isolation within a tenant. For more information, see Configure resource isolation within a tenant.

References

• Configure cgroups

• Configure resource isolation within a tenant