resource control: support more mode for BURSTABLE

information-schema/information-schema-resource-groups.md

@@ -17,15 +17,17 @@ DESC resource_groups;
 ```
 
 ```sql
-+------------+-------------+------+------+---------+-------+
-| Field      | Type        | Null | Key  | Default | Extra |
-+------------+-------------+------+------+---------+-------+
-| NAME       | varchar(32) | NO   |      | NULL    |       |
-| RU_PER_SEC | bigint(21)  | YES  |      | NULL    |       |
-| PRIORITY   | varchar(6)  | YES  |      | NULL    |       |
-| BURSTABLE  | varchar(3)  | YES  |      | NULL    |       |
-+------------+-------------+------+------+---------+-------+
-3 rows in set (0.00 sec)
++-------------+--------------+------+------+---------+-------+
+| Field       | Type         | Null | Key  | Default | Extra |
++-------------+--------------+------+------+---------+-------+
+| NAME        | varchar(32)  | NO   |      | NULL    |       |
+| RU_PER_SEC  | varchar(21)  | YES  |      | NULL    |       |
+| PRIORITY    | varchar(6)   | YES  |      | NULL    |       |
+| BURSTABLE   | varchar(3)   | YES  |      | NULL    |       |
+| QUERY_LIMIT | varchar(256) | YES  |      | NULL    |       |
+| BACKGROUND  | varchar(256) | YES  |      | NULL    |       |
++-------------+--------------+------+------+---------+-------+
+6 rows in set (0.00 sec)
 ```
 
 ## Examples
@@ -35,11 +37,11 @@ SELECT * FROM information_schema.resource_groups; -- View all resource groups. T
 ```
 
 ```sql
-+---------+------------+----------+-----------+
-| NAME    | RU_PER_SEC | PRIORITY | BURSTABLE |
-+---------+------------+----------+-----------+
-| default | UNLIMITED  | MEDIUM   | YES       |
-+---------+------------+----------+-----------+
++---------+------------+----------+----------------+-------------+------------+
+| NAME    | RU_PER_SEC | PRIORITY | BURSTABLE      | QUERY_LIMIT | BACKGROUND |
++---------+------------+----------+----------------+-------------+------------+
+| default | UNLIMITED  | MEDIUM   | YES(UNLIMITED) | NULL        | NULL       |
++---------+------------+----------+----------------+-------------+------------+
 ```
 
 ```sql
@@ -68,11 +70,11 @@ SELECT * FROM information_schema.resource_groups WHERE NAME = 'rg1'; -- View the
 ```
 
 ```sql
-+------+------------+----------+-----------+-------------+
-| NAME | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT |
-+------+------------+----------+-----------+-------------+
-| rg1  | 1000       | MEDIUM   | NO        | NULL        |
-+------+------------+----------+-----------+-------------+
++------+------------+----------+-----------+-------------+------------+
+| NAME | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT | BACKGROUND |
++------+------------+----------+-----------+-------------+------------+
+| rg1  | 1000       | MEDIUM   | NO        | NULL        | NULL       |
++------+------------+----------+-----------+-------------+------------+
 1 row in set (0.00 sec)
 ```
 
@@ -81,8 +83,12 @@ The descriptions of the columns in the `RESOURCE_GROUPS` table are as follows:
 * `NAME`: the name of the resource group.
 * `RU_PER_SEC`: the backfilling speed of the resource group. The unit is RU/second, in which RU means [Request Unit](/tidb-resource-control-ru-groups.md#what-is-request-unit-ru).
 * `PRIORITY`: the absolute priority of tasks to be processed on TiKV. Different resources are scheduled according to the `PRIORITY` setting. Tasks with high `PRIORITY` are scheduled first. For resource groups with the same `PRIORITY`, tasks will be scheduled proportionally according to the `RU_PER_SEC` configuration. If `PRIORITY` is not specified, the default priority is `MEDIUM`.
-* `BURSTABLE`: whether to allow the resource group to overuse the available system resources.
+* `BURSTABLE`: whether to allow the resource group to overuse the available remaining system resources. The following three modes are supported. If no value is specified for `BURSTABLE`, the `MODERATED` mode is enabled by default.
+
+    - `OFF`: indicates that the resource group is not allowed to overuse any remaining system resources.
+    - `MODERATED`: indicates that the resource group is allowed to overuse remaining system resources to a limited extent, with priority given to allocated resources within its quota.
+    - `UNLIMITED`: indicates that the resource group can overuse remaining system resources without limitation, and the excess system resources are treated as equal to the resources within the quota during allocation.
 
 > **Note:**
 >
-> TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and it is in `BURSTABLE` mode. All requests that are not bound to any resource group are automatically bound to this `default` resource group. When you create a new configuration for another resource group, it is recommended to modify the `default` resource group configuration as needed.
+> TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and its `BURSTABLE` mode is `UNLIMITED`. All requests that are not bound to any resource group are automatically bound to this `default` resource group. You cannot delete the `default` resource group, but can modify its RU configuration.

sql-statements/sql-statement-alter-resource-group.md

@@ -33,7 +33,9 @@ DirectResourceGroupOption ::=
     "RU_PER_SEC" EqOpt LengthNum
 |   "PRIORITY" EqOpt ResourceGroupPriorityOption
 |   "BURSTABLE"
-|   "BURSTABLE" EqOpt Boolean
+|   "BURSTABLE" EqOpt "MODERATED"
+|   "BURSTABLE" EqOpt "UNLIMITED"
+|   "BURSTABLE" EqOpt "OFF"
 |   "QUERY_LIMIT" EqOpt '(' ResourceGroupRunawayOptionList ')'
 |   "QUERY_LIMIT" EqOpt '(' ')'
 |   "QUERY_LIMIT" EqOpt "NULL"
@@ -84,7 +86,7 @@ TiDB supports the following `DirectResourceGroupOption`, where [Request Unit (RU
 |---------------|-------------------------------------|------------------------|
 | `RU_PER_SEC` | Rate of RU backfilling per second | `RU_PER_SEC = 500` indicates that this resource group is backfilled with 500 RUs per second |
 | `PRIORITY`    | The absolute priority of tasks to be processed on TiKV  | `PRIORITY = HIGH` indicates that the priority is high. If not specified, the default value is `MEDIUM`. |
-| `BURSTABLE`   | If the `BURSTABLE` attribute is set, TiDB allows the corresponding resource group to use the available system resources when the quota is exceeded. |
+| `BURSTABLE`   | Whether to allow the resource group to overuse the available remaining system resources | Three modes are supported. `OFF` indicates that the resource group is not allowed to overuse any remaining system resources. `MODERATED` indicates that the resource group is allowed to overuse remaining system resources to a limited extent. `UNLIMITED` indicates that the resource group can overuse remaining system resources without limitation. If no value is specified for `BURSTABLE`, the `MODERATED` mode is enabled by default. |
 | `QUERY_LIMIT` | When the query execution meets this condition, the query is identified as a runaway query and the corresponding action is executed. | `QUERY_LIMIT=(EXEC_ELAPSED='60s', ACTION=KILL, WATCH=EXACT DURATION='10m')` indicates that the query is identified as a runaway query when the execution time exceeds 60 seconds. The query is terminated. All SQL statements with the same SQL text will be terminated immediately in the coming 10 minutes. `QUERY_LIMIT=()` or `QUERY_LIMIT=NULL` means that runaway control is not enabled. See [Runaway Queries](/tidb-resource-control-runaway-queries.md). |
 | `BACKGROUND`  | Configure the background tasks. For more details, see [Manage background tasks](/tidb-resource-control-background-tasks.md). | `BACKGROUND=(TASK_TYPES="br,stats", UTILIZATION_LIMIT=30)` indicates that the backup and restore and statistics collection related tasks are scheduled as background tasks, and background tasks can consume 30% of the TiKV resources at most. |
 
@@ -168,11 +170,11 @@ SELECT * FROM information_schema.resource_groups WHERE NAME ='default';
 ```
 
 ```sql
-+---------+------------+----------+-----------+-------------+-------------------------------------------+
-| NAME    | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT | BACKGROUND                                |
-+---------+------------+----------+-----------+-------------+-------------------------------------------+
-| default | UNLIMITED  | MEDIUM   | YES       | NULL        | TASK_TYPES='br,ddl', UTILIZATION_LIMIT=30 |
-+---------+------------+----------+-----------+-------------+-------------------------------------------+
++---------+------------+----------+----------------------+-------------+-------------------------------------------+
+| NAME    | RU_PER_SEC | PRIORITY | BURSTABLE            | QUERY_LIMIT | BACKGROUND                                |
++---------+------------+----------+----------------------+-------------+-------------------------------------------+
+| default | UNLIMITED  | MEDIUM   | YES(UNLIMITED)       | NULL        | TASK_TYPES='br,ddl', UTILIZATION_LIMIT=30 |
++---------+------------+----------+----------------------+-------------+-------------------------------------------+
 1 rows in set (1.30 sec)
 ```
 

sql-statements/sql-statement-create-resource-group.md

@@ -33,7 +33,9 @@ DirectResourceGroupOption ::=
     "RU_PER_SEC" EqOpt stringLit
 |   "PRIORITY" EqOpt ResourceGroupPriorityOption
 |   "BURSTABLE"
-|   "BURSTABLE" EqOpt Boolean
+|   "BURSTABLE" EqOpt "MODERATED"
+|   "BURSTABLE" EqOpt "UNLIMITED"
+|   "BURSTABLE" EqOpt "OFF"
 |   "QUERY_LIMIT" EqOpt '(' ResourceGroupRunawayOptionList ')'
 |   "QUERY_LIMIT" EqOpt '(' ')'
 |   "QUERY_LIMIT" EqOpt "NULL"
@@ -81,13 +83,13 @@ TiDB supports the following `DirectResourceGroupOption`, where [Request Unit (RU
 |---------------|-------------------------------------|------------------------|
 | `RU_PER_SEC`  | Rate of RU backfilling per second   | `RU_PER_SEC = 500` indicates that this resource group is backfilled with 500 RUs per second    |
 | `PRIORITY`    | The absolute priority of tasks to be processed on TiKV  | `PRIORITY = HIGH` indicates that the priority is high. If not specified, the default value is `MEDIUM`. |
-| `BURSTABLE`   | If the `BURSTABLE` attribute is set, TiDB allows the corresponding resource group to use the available system resources when the quota is exceeded. |
+| `BURSTABLE`   | Whether to allow the resource group to overuse the available remaining system resources | Three modes are supported. `OFF` indicates that the resource group is not allowed to overuse any remaining system resources. `MODERATED` indicates that the resource group is allowed to overuse remaining system resources to a limited extent. `UNLIMITED` indicates that the resource group can overuse remaining system resources without limitation. If no value is specified for `BURSTABLE`, the `MODERATED` mode is enabled by default. |
 | `QUERY_LIMIT` | When the query execution meets this condition, the query is identified as a runaway query and the corresponding action is executed. | `QUERY_LIMIT=(EXEC_ELAPSED='60s', ACTION=KILL, WATCH=EXACT DURATION='10m')` indicates that the query is identified as a runaway query when the execution time exceeds 60 seconds. The query is terminated. All SQL statements with the same SQL text will be terminated immediately in the coming 10 minutes. `QUERY_LIMIT=()` or `QUERY_LIMIT=NULL` means that runaway control is not enabled. See [Runaway Queries](/tidb-resource-control-runaway-queries.md). |
 
 > **Note:**
 >
 > - The `CREATE RESOURCE GROUP` statement can only be executed when the global variable [`tidb_enable_resource_control`](/system-variables.md#tidb_enable_resource_control-new-in-v660) is set to `ON`.
-> TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and it is in `BURSTABLE` mode. All requests that are not bound to any resource group are automatically bound to this `default` resource group. When you create a new configuration for another resource group, it is recommended to modify the `default` resource group configuration as needed.
+> TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and its `BURSTABLE` mode is `UNLIMTED`. All requests that are not bound to any resource group are automatically bound to this `default` resource group. You cannot delete the `default` resource group, but can modify its RU configuration.
 > - Currently, only the `default` resource group supports modifying the `BACKGROUND` configuration.
 
 ## Examples
@@ -127,12 +129,12 @@ SELECT * FROM information_schema.resource_groups WHERE NAME ='rg1' or NAME = 'rg
 ```
 
 ```sql
-+------+------------+----------+-----------+---------------------------------+
-| NAME | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT                     |
-+------+------------+----------+-----------+---------------------------------+
-| rg1  | 100        | HIGH     | YES       | NULL                            |
-| rg2  | 200        | MEDIUM   | NO        | EXEC_ELAPSED=100ms, ACTION=KILL |
-+------+------------+----------+-----------+---------------------------------+
++------+------------+----------+----------------------+---------------------------------+
+| NAME | RU_PER_SEC | PRIORITY | BURSTABLE            | QUERY_LIMIT                     |
++------+------------+----------+----------------------+---------------------------------+
+| rg1  | 100        | HIGH     | YES(MODERATED)       | NULL                            |
+| rg2  | 200        | MEDIUM   | NO                   | EXEC_ELAPSED=100ms, ACTION=KILL |
++------+------------+----------+----------------------+---------------------------------+
 2 rows in set (1.30 sec)
 ```
 

sql-statements/sql-statement-drop-resource-group.md

@@ -55,11 +55,11 @@ SELECT * FROM information_schema.resource_groups WHERE NAME ='rg1';
 ```
 
 ```sql
-+------+------------+----------+-----------+-------------+
-| NAME | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT |
-+------+------------+----------+-----------+-------------+
-| rg1  | 500        | MEDIUM   | YES       | NULL        |
-+------+------------+----------+-----------+-------------+
++------+------------+----------+----------------------+-------------+
+| NAME | RU_PER_SEC | PRIORITY | BURSTABLE            | QUERY_LIMIT |
++------+------------+----------+----------------------+-------------+
+| rg1  | 500        | MEDIUM   | YES(MODERATED)       | NULL        |
++------+------------+----------+----------------------+-------------+
 1 row in set (0.01 sec)
 ```
 

tidb-resource-control-background-tasks.md

@@ -77,11 +77,11 @@ By default, the task types that are marked as background tasks are `""`, and the
     The output is as follows:
 
     ```
-    +---------+------------+----------+-----------+-------------+-------------------------------------------+
-    | NAME    | RU_PER_SEC | PRIORITY | BURSTABLE | QUERY_LIMIT | BACKGROUND                                |
-    +---------+------------+----------+-----------+-------------+-------------------------------------------+
-    | default | UNLIMITED  | MEDIUM   | YES       | NULL        | TASK_TYPES='br,ddl', UTILIZATION_LIMIT=30 |
-    +---------+------------+----------+-----------+-------------+-------------------------------------------+
+    +---------+------------+----------+----------------------+-------------+-------------------------------------------+
+    | NAME    | RU_PER_SEC | PRIORITY | BURSTABLE            | QUERY_LIMIT | BACKGROUND                                |
+    +---------+------------+----------+----------------------+-------------+-------------------------------------------+
+    | default | UNLIMITED  | MEDIUM   | YES(UNLIMITED)       | NULL        | TASK_TYPES='br,ddl', UTILIZATION_LIMIT=30 |
+    +---------+------------+----------+----------------------+-------------+-------------------------------------------+
     ```
 
 5. To explicitly mark tasks in the current session as the background type, you can use `tidb_request_source_type` to explicitly specify the task type. The following is an example:

tidb-resource-control-ru-groups.md

@@ -185,7 +185,7 @@ You can delete a resource group by using [`DROP RESOURCE GROUP`](/sql-statements
 
 The following is an example of how to create a resource group.
 
-1. Create a resource group `rg1`. The resource limit is 500 RUs per second and allows applications in this resource group to overrun resources.
+1. Create a resource group `rg1`. The resource limit is 500 RUs per second and allows applications in this resource group to overrun resources. If no value is specified for `BURSTABLE`, the `MODERATED` mode is enabled by default.
 
     ```sql
     CREATE RESOURCE GROUP IF NOT EXISTS rg1 RU_PER_SEC = 500 BURSTABLE;
@@ -203,6 +203,12 @@ The following is an example of how to create a resource group.
     CREATE RESOURCE GROUP IF NOT EXISTS rg3 RU_PER_SEC = 100 PRIORITY = HIGH;
     ```
 
+4. Create a `rg4` resource group with a quota of 500 RUs per second, and allow applications in this group to use additional resources beyond the quota by setting the `BURSTABLE` mode to `UNLIMITED`.
+
+    ```sql 
+    CREATE RESOURCE GROUP IF NOT EXISTS rg4 RU_PER_SEC = 500 BURSTABLE=UNLIMITED; 
+    ```
+
 ### Bind resource groups
 
 TiDB supports three levels of resource group settings as follows.
@@ -232,7 +238,7 @@ If there are too many requests that result in insufficient resources for the res
 > **Note:**
 >
 > - When you bind a user to a resource group by using `CREATE USER` or `ALTER USER`, it will not take effect for the user's existing sessions, but only for the user's new sessions.
-> - TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and it is in `BURSTABLE` mode. Statements that are not bound to a resource group are automatically bound to this resource group. This resource group does not support deletion, but you can modify the configuration of its RU.
+> - TiDB automatically creates a `default` resource group during cluster initialization. For this resource group, the default value of `RU_PER_SEC` is `UNLIMITED` (equivalent to the maximum value of the `INT` type, that is, `2147483647`) and its `BURSTABLE` is `UNLIMITED` mode. All requests that are not bound to any resource group are automatically bound to this `default` resource group. You cannot delete the `default` resource group, but can modify its RU configuration.
 
 To unbind users from a resource group, you can simply bind them to the `default` group again as follows: