Database Autonomy Service:SQL throttling

Scenarios

Throttling modes

Procedure

1. Log on to the DAS console.

2. In the left-side navigation pane, click Instance Monitoring.

3. On the page that appears, find the database instance that you want to manage and click the instance ID. The instance details page appears.

4. In the left-side navigation pane, click Instance Sessions.

5. On the Session Management tab, click SQL Throttling in the Instance Sessions section.

   

6. In the SQL Throttling dialog box, configure the parameters described in the following table.

   Parameter	Description
   Throttling Mode	The mode that you want to use to throttle SQL statements. Select a throttling mode based on your business requirements. For more information, see the Throttling modes section of this topic.
   SQL Type	The type of SQL statements that you want to throttle. Valid values: SELECT, UPDATE, DELETE, and INSERT. Note The INSERT SQL statements can be throttled on one of the following database engines: ApsaraDB RDS for MySQL 8.0 PolarDB for MySQL 5.7 and 8.0 PolarDB-X 2.0 SQL statements that are in the INSERT...SELECT... format cannot be throttled.
   Maximum Concurrency	The maximum number of concurrent SQL statements. The minimum value of this parameter is 1. Throttling is triggered when the number of SQL statements that are concurrently executed and meet the throttling policy reaches the maximum value.
   Throttling Duration	The duration during which the SQL throttling rule takes effect. The throttling feature is intended only for emergency use. We recommend that you specify the throttling duration based on your business requirements and disable throttling when it is no longer needed.
   SQL Keywords	The keywords that are used to identify the SQL statements that need to be throttled. Note This parameter takes effect only when the Throttling Mode parameter is set to Throttled by Keywords. If you specify multiple keywords, throttling is triggered only if an SQL statement contains all of the specified keywords. Multiple keywords are separated by tildes (~) with no sequential restriction. The SQL Keywords parameter cannot be set only to SELECT, UPDATE, or DELETE. The keywords are case-sensitive for instances except for the instances of some earlier versions. For example, if the original SQL statement to be throttled is SELECT min(id), max(id) FROM task_event WHERE gmt_modified < '2020-06-21' AND begin_time > '2020-07-09' AND source IN (527) AND id >= 15673 AND id <= 8015673, set this parameter to SELECT~min~id~max~id~FROM~task_event~WHERE~gmt_modified~AND~begin_time~AND~source~IN~AND~id~AND~id.
   Template ID	The ID of an SQL template used by an SQL statement that you want to throttle. Separate multiple IDs with commas (,). Note This parameter takes effect only when the Throttling Mode parameter is set to Throttled by SQL Template ID.
   Executed At	The threshold value of the execution duration. If the execution duration of an SQL statement exceeds the specified threshold value, the system fetches the ID of the SQL template used by the SQL statement and adds the ID to the throttling rule. Note This parameter takes effect only when the Throttling Mode parameter is set to Throttled by Execution Duration.
   Maximum Number of Throttled Queries	The maximum number of IDs of SQL templates used by SQL statements throttled by execution duration. After the number of SQL template IDs added to the throttling rule reaches the upper limit, the system stops fetching IDs of SQL templates used by SQL statements whose execution duration exceeds the specified threshold value. Note This parameter takes effect only when the Throttling Mode parameter is set to Throttled by Execution Duration.
   Database Account with Throttled Queries	The database account to which the throttled SQL statement belongs. Note This parameter takes effect only when the database instance for which you want to enable SQL throttling is a PolarDB-X 2.0 instance and the Throttling Mode parameter is set to Throttled by Keywords or Throttled by SQL Template ID.

   Note

   After the SQL throttling rule is created, different types of database services behave in different manners when they respond to requests sent for SQL statements that contain all specified keywords.

   • For an ApsaraDB RDS for MySQL instance that runs MySQL 5.6 or 5.7 or a PolarDB for MySQL cluster that runs MySQL 5.6, the corresponding database system returns error code 1317 and the "query execution was interrupted" error message.

   • For an ApsaraDB RDS for MySQL instance that runs MySQL 8.0 or a PolarDB for MySQL cluster that runs MySQL 5.7 or 8.0, the SQL statements enter the Concurrency control waiting state. If the version of your database instance supports the ccl_max_waiting_count parameter, the corresponding database system returns one of the following error codes and the "Concurrency control waiting count exceed max waiting count" error message when the number of SQL statements in the Concurrency control waiting state exceeds the threshold specified by the ccl_max_waiting_count parameter:

     • ERROR 7534 (HY000) for an ApsaraDB RDS for MySQL instance that runs MySQL 8.0

     • ERROR 3277 (HY000) for a PolarDB for MySQL cluster that runs MySQL 5.7

     • ERROR 7533 (HY000) for a PolarDB for MySQL cluster that runs MySQL 8.0

     If the ccl_max_waiting_count parameter is set to the default value 0, all throttled SQL statements are in the Concurrency control waiting state and no error code is returned. When DAS performs SQL throttling, DAS sets the ccl_max_waiting_count parameter to the default value that is defined in DAS if the value of the ccl_max_waiting_count parameter is 0 or directly uses the value of the ccl_max_waiting_count parameter if the value is greater than 0.

7. Click Create.

   After the SQL throttling rule is created, you can view the information about the rule on the Running tab.

   To disable or modify a throttling rule, click Disable or Edit in the Actions column.

References

Configure automatic SQL throttling

Related API operations