Information Schema THREAD_POOL_QUEUES Table
MariaDB starting with 10.5
The Information Schema THREAD_POOL_QUEUES table was introduced in MariaDB 10.5.0.
The table provides information about thread pool queues, and contains the following columns:
| Column | Description |
|---|---|
GROUP_ID | the thread group this row is showing data for |
POSITION | position in the groups queue |
PRIORITY | request priority, see priority scheduling |
CONNECTION_ID | ID of the client connection that submitted the queued request |
QUEUEING_TIME_MICROSECONDS | how long the request has already been waiting in the queue in microseconds |
Setting thread_poll_exact_stats will provides better queueing time statistics by using a high precision timestamp, at a small performance cost, for the time when the connection was added to the queue. This timestamp helps calculate the queuing time shown in the table.
Setting thread_pool_dedicated_listener will give each group its own dedicated listener, and the listener thread will not pick up work items. As a result, the queueing time in the table will be more exact, since IO requests are immediately dequeued from poll, without delay.
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