resource control: support more mode for BURSTABLE #21138
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Signed-off-by: lhy1024 <[email protected]>
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Hello @lhy1024, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!
Summary of Changes
Hello! I'm gemini-code-assist, here to provide a summary of this pull request. This PR primarily focuses on updating the documentation related to TiDB's resource control feature. Specifically, it introduces and documents the support for more granular modes for the BURSTABLE option within resource groups. The changes involve updating the syntax descriptions for CREATE RESOURCE GROUP and ALTER RESOURCE GROUP statements, as well as clarifying the behavior and available modes (OFF, MODERATED, UNLIMITED) for BURSTABLE in the documentation for the INFORMATION_SCHEMA.RESOURCE_GROUPS table. Several examples showing the output of querying INFORMATION_SCHEMA.RESOURCE_GROUPS are also updated to reflect the new BURSTABLE output format and include columns for QUERY_LIMIT and BACKGROUND.
Highlights
- Documentation Updates: Documentation for
CREATE RESOURCE GROUP,ALTER RESOURCE GROUP, andINFORMATION_SCHEMA.RESOURCE_GROUPSis modified to include the newBURSTABLEmodes and their descriptions. - Example Updates: Examples showing the output of
SELECT * FROM information_schema.resource_groupsare updated to display the newBURSTABLEformat (e.g.,YES(UNLIMITED)) and include theQUERY_LIMITandBACKGROUNDcolumns.
Changelog
Click here to see the changelog
- information-schema/information-schema-resource-groups.md
- Updated example output for
DESC resource_groups;to includeQUERY_LIMITandBACKGROUNDcolumns and changeRU_PER_SECtype display frombigint(21)tovarchar(21)(lines 20-29). - Updated example output for
SELECT * FROM information_schema.resource_groups;to includeQUERY_LIMITandBACKGROUNDcolumns and showBURSTABLEasYES(UNLIMITED)for the default group (lines 40-44). - Updated example output for
SELECT * FROM information_schema.resource_groups WHERE NAME = 'rg1';to includeQUERY_LIMITandBACKGROUNDcolumns (lines 73-77). - Updated the description of the
BURSTABLEcolumn to explain theOFF,MODERATED, andUNLIMITEDmodes and clarify the default mode for thedefaultresource group (lines 86-90).
- Updated example output for
- sql-statements/sql-statement-alter-resource-group.md
- Updated the grammar definition for
ALTER RESOURCE GROUPto explicitly listMODERATED,UNLIMITED, andOFFas valid options forBURSTABLE(lines 36-38). - Updated the description table for
DirectResourceGroupOptionto explain the threeBURSTABLEmodes and the default behavior (lines 89). - Updated example output for
SELECT * FROM information_schema.resource_groups WHERE NAME ='default';to showBURSTABLEasYES(UNLIMITED)(lines 173-177).
- Updated the grammar definition for
- sql-statements/sql-statement-create-resource-group.md
- Updated the grammar definition for
CREATE RESOURCE GROUPto explicitly listMODERATED,UNLIMITED, andOFFas valid options forBURSTABLE(lines 36-38). - Updated the description table for
DirectResourceGroupOptionto explain the threeBURSTABLEmodes and the default behavior (lines 86). - Clarified the default
BURSTABLEmode for thedefaultresource group isUNLIMITEDin the note section (line 92). - Added a new example for creating a resource group with
BURSTABLE=UNLIMITED(lines 206-210). - Updated example output for
SELECT * FROM information_schema.resource_groups WHERE NAME ='rg1' or NAME = 'rg2';to showBURSTABLEasYES(MODERATED)forrg1andNOforrg2(lines 132-137).
- Updated the grammar definition for
- sql-statements/sql-statement-drop-resource-group.md
- Updated example output for
SELECT * FROM information_schema.resource_groups WHERE NAME ='rg1';to showBURSTABLEasYES(MODERATED)(lines 58-62).
- Updated example output for
- tidb-resource-control-background-tasks.md
- Updated example output for
SELECT * FROM information_schema.resource_groups;to showBURSTABLEasYES(UNLIMITED)for the default group (lines 80-84).
- Updated example output for
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Code Review
This pull request updates the documentation to reflect the new modes available for the BURSTABLE option in resource groups. The changes are mostly in table outputs and descriptions across several files. Overall, the updates clarify the new functionality. However, there are a few areas that need attention to ensure accuracy and consistency, primarily related to example outputs and a typo.
Summary of Findings
- Documentation Accuracy: There's an incorrect row count in the
DESC resource_groups;output ininformation-schema/information-schema-resource-groups.md. - Spelling Error: A typo "UNLIMTED" was found in
sql-statements/sql-statement-create-resource-group.md. It should be "UNLIMITED". - Example Consistency: In
tidb-resource-control-ru-groups.md, an example description refers torg1while the SQL code createsrg4. - Readability: The description of the
BURSTABLEoption is quite long in several files and could be broken down for better readability. - Formatting Consistency: EBNF diagrams in
sql-statement-alter-resource-group.mdandsql-statement-create-resource-group.mdhave inconsistent indentation for the newBURSTABLEoptions.
Merge Readiness
The pull request introduces important documentation updates for the BURSTABLE resource control option. While the changes are largely good, there are a few issues related to accuracy (incorrect command output, typo) and consistency (example naming) that should be addressed before merging. Addressing these will improve the clarity and correctness of the documentation. I am unable to approve pull requests, so please ensure these changes are reviewed and approved by a maintainer.
| | BURSTABLE | varchar(3) | YES | | NULL | | | ||
| | QUERY_LIMIT | varchar(256) | YES | | NULL | | | ||
| | BACKGROUND | varchar(256) | YES | | NULL | | | ||
| +-------------+--------------+------+------+---------+-------+ | ||
| 3 rows in set (0.00 sec) |
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The output of DESC resource_groups; indicates 3 rows in set, but the table now lists 6 fields (NAME, RU_PER_SEC, PRIORITY, BURSTABLE, QUERY_LIMIT, BACKGROUND). Shouldn't this be 6 rows in set to accurately reflect the number of fields described? 1
Style Guide References
| 3 rows in set (0.00 sec) | |
| 6 rows in set (0.00 sec) |
Footnotes
| | `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). | | ||
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| > **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. When you create a new configuration for another resource group, it is recommended to modify the `default` resource group configuration as needed. |
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There's a typo here: "UNLIMTED" should be "UNLIMITED". 1
Style Guide References
| > 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. 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. When you create a new configuration for another resource group, it is recommended to modify the `default` resource group configuration as needed. |
Footnotes
| @@ -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; | |||
| ``` | |||
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| 4. Create a resource group `rg1`. The resource limit is 500 RUs per second and allows applications in this resource group to overrun resources with `UNLIMITED` mode. | |||
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The description mentions creating a resource group rg1, but the SQL example creates rg4. To avoid confusion, should the description also refer to rg4? 1
Style Guide References
| 4. Create a resource group `rg1`. The resource limit is 500 RUs per second and allows applications in this resource group to overrun resources with `UNLIMITED` mode. | |
| 4. Create a resource group `rg4`. The resource limit is 500 RUs per second and allows applications in this resource group to overrun resources with `UNLIMITED` mode. |
Footnotes
| @@ -81,8 +83,8 @@ 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 system resources. There are three modes, `OFF`, which means this resource group is not allowed to overuse the remaining system resources; `MODERATED`, which means this resource group is allowed to overuse the remaining system resources in a limited way; and `UNLIMITED`, which means this resource group is allowed to overuse the remaining system resources in an unlimited way. If no target value is specified for `BURSTABLE`, `MODERATED` is enabled by default. | |||
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The description for BURSTABLE is quite long. For better readability 1, consider breaking it down. For example:
"* BURSTABLE: Specifies whether the resource group can overuse available system resources. It supports three modes:
* OFF: The resource group cannot overuse remaining system resources.
* MODERATED: The resource group can overuse remaining system resources in a limited way. This is the default mode if BURSTABLE is specified without a value.
* UNLIMITED: The resource group can overuse remaining system resources in an unlimited way."
Style Guide References
Footnotes
| | "BURSTABLE" | ||
| | "BURSTABLE" EqOpt "MODERATED" | ||
| | "BURSTABLE" EqOpt "UNLIMITED" | ||
| | "BURSTABLE" EqOpt "OFF" |
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The indentation for the new BURSTABLE options in the EBNF diagram uses tabs, while other options like RU_PER_SEC and PRIORITY use spaces. For consistency within the EBNF block, could these also use spaces for indentation? 1
Style Guide References
| | "BURSTABLE" | |
| | "BURSTABLE" EqOpt "MODERATED" | |
| | "BURSTABLE" EqOpt "UNLIMITED" | |
| | "BURSTABLE" EqOpt "OFF" | |
| | "BURSTABLE" | |
| | "BURSTABLE" EqOpt "MODERATED" | |
| | "BURSTABLE" EqOpt "UNLIMITED" | |
| | "BURSTABLE" EqOpt "OFF" |
Footnotes
| @@ -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` | TiDB allows the corresponding resource group to use the available system resources when the quota is exceeded. There are three modes, `OFF`, which means this resource group is not allowed to overuse the remaining system resources; `MODERATED`, which means this resource group is allowed to overuse the remaining system resources in a limited way; and `UNLIMITED`, which means this resource group is allowed to overuse the remaining system resources in an unlimited way. If no target value is specified for `BURSTABLE`, `MODERATED` is enabled by default. | | |||
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Similar to the comment in information-schema-resource-groups.md, this description for BURSTABLE is a bit long. Could it be broken down for improved readability? 1
For example:
"TiDB allows the corresponding resource group to use available system resources when the quota is exceeded. There are three modes:
OFF: This resource group is not allowed to overuse the remaining system resources.MODERATED: This resource group is allowed to overuse the remaining system resources in a limited way. If no target value is specified forBURSTABLE,MODERATEDis enabled by default.UNLIMITED: This resource group is allowed to overuse the remaining system resources in an unlimited way."
Style Guide References
Footnotes
| | "BURSTABLE" | ||
| | "BURSTABLE" EqOpt "MODERATED" | ||
| | "BURSTABLE" EqOpt "UNLIMITED" | ||
| | "BURSTABLE" EqOpt "OFF" |
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The indentation for the new BURSTABLE options in the EBNF diagram uses tabs, while other options use spaces. For consistency, could these also use spaces? 1
Style Guide References
| | "BURSTABLE" | |
| | "BURSTABLE" EqOpt "MODERATED" | |
| | "BURSTABLE" EqOpt "UNLIMITED" | |
| | "BURSTABLE" EqOpt "OFF" | |
| | "BURSTABLE" | |
| | "BURSTABLE" EqOpt "MODERATED" | |
| | "BURSTABLE" EqOpt "UNLIMITED" | |
| | "BURSTABLE" EqOpt "OFF" |
Footnotes
| @@ -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` | TiDB allows the corresponding resource group to use the available system resources when the quota is exceeded. There are three modes, `OFF`, which means this resource group is not allowed to overuse the remaining system resources; `MODERATED`, which means this resource group is allowed to overuse the remaining system resources in a limited way; and `UNLIMITED`, which means this resource group is allowed to overuse the remaining system resources in an unlimited way. If no target value is specified for `BURSTABLE`, `MODERATED` is enabled by default. | | |||
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