Description
ha_low_thread_score specifies the current number of high-availability low-priority worker threads.
Note
This parameter is available since OceanBase Database V4.0.0.
Related parameters
ha_high_thread_scoreha_mid_thread_score
Attributes
Attribute |
Description |
|---|---|
| Type | Integer |
| Default value | 0 |
| Value range | [0, 100] |
| Effective upon OBServer node restart | No |
Considerations
In OceanBase Database V4.x, each priority queue contains a specific type of DAG tasks, and uses the first in, first out (FIFO) strategy to schedule the time slices of the threads for DAG tasks. Each priority queue is assigned a weight when it is initialized. A processor sharing algorithm similar to CGroup is used to allocate DagScheduler resources between priority queues. A queue with a greater weight is more likely to be scheduled. You can increase the concurrency of threads of a priority queue by modifying the weight of the queue to meet a specific need, such as accelerating the minor or major compactions.
In OceanBase Database V4.x, tasks related to high reliability (HA), such as migration, replication, backup, and restore, are scheduled by the tenant-level DagScheduler. Considering the limited thread resources of each tenant, parameters are no longer provided based on the specific task type. Instead, OceanBase Database provides the following three HA parameters based on the task type, priority, and significance:
ha_high_thread_score: specifies the number of concurrent threads for high-priority and high-reliability task queues, such as replication, rebuilding, and restore tasks.ha_mid_thread_score: specifies the number of concurrent threads for medium-priority and high-reliability task queues such as migration tasks.ha_low_thread_score: specifies the number of concurrent threads for low-priority and high-reliability task queues, such as backup, second backup, and backup cleanup tasks.