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. 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	Select the SQL throttling mode based on your business requirements. For more information, see Throttling modes.
   SQL Type	Select 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 Throttling Mode 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 Throttling Mode is set to Throttled by SQL Template ID.
   Execution Duration	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 Throttling Mode 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 Throttling Mode 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 Throttling Mode 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 respond to requests sent for SQL statements that contain all specified keywords in a different manner.

   • For an ApsaraDB RDS for MySQL instance that runs MySQL 5.6 or V5.7 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 MySQL 8.0, the SQL statements enter the Concurrency control waiting state. After the number of SQL statements that are in the Concurrency control waiting state exceeds the threshold specified by the ccl_max_waiting_count parameter if the version of your instance supports the ccl_max_waiting_count parameter, the corresponding database system returns the following error code together with the "Concurrency control waiting count exceed max waiting count" error message:
     • ERROR 7534 (HY000) for ApsaraDB RDS for MySQL 8.0
     • ERROR 3277 (HY000) for PolarDB for MySQL 5.7
     • ERROR 7533 (HY000) for PolarDB for MySQL 8.0

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

7. Click Create.
   After the SQL throttling rule is created, you can view the status of the rule in the list of throttling rules.

   If you want to disable or modify a throttling rule before the specified throttling duration expires, click Disable or Edit in the Actions column corresponding to the throttling rule.

References

Automatic SQL throttling

Related API operations

• EnableSqlConcurrencyControl
• DisableSqlConcurrencyControl
• DisableAllSqlConcurrencyControlRules
• GetRunningSqlConcurrencyControlRules
• GetSqlConcurrencyControlRulesHistory
• GetSqlConcurrencyControlKeywordsFromSqlText