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E-MapReduce:ModifyNodeNumber

Last Updated:Aug 11, 2026

Modifies the number of nodes in a compute group of a Serverless StarRocks instance.

Operation description

Before using this operation, make sure that you fully understand the billing method and billable items of Serverless StarRocks. When calling this operation, note the following:

  • Only Standard Standard instances support modifying the number of compute group nodes. Basic Standard instances do not support this operation.

  • The instance must be in the Running state.

  • The number of FE nodes cannot be an even number, and FE nodes do not support scale-in.

After modifying the node count, billing changes are as follows:

  • Pay-as-you-go: Billed based on the new node count.

  • Subscription: Within the billing cycle, the additional fee is calculated based on the price difference between the old and new configurations and the remaining days (from 00:00 of the next day to the end of the validity period).

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RAM authorization

The table below describes the authorization required to call this API. You can define it in a Resource Access Management (RAM) policy. The table's columns are detailed below:

  • Action: The actions can be used in the Action element of RAM permission policy statements to grant permissions to perform the operation.

  • API: The API that you can call to perform the action.

  • Access level: The predefined level of access granted for each API. Valid values: create, list, get, update, and delete.

  • Resource type: The type of the resource that supports authorization to perform the action. It indicates if the action supports resource-level permission. The specified resource must be compatible with the action. Otherwise, the policy will be ineffective.

    • For APIs with resource-level permissions, required resource types are marked with an asterisk (*). Specify the corresponding Alibaba Cloud Resource Name (ARN) in the Resource element of the policy.

    • For APIs without resource-level permissions, it is shown as All Resources. Use an asterisk (*) in the Resource element of the policy.

  • Condition key: The condition keys defined by the service. The key allows for granular control, applying to either actions alone or actions associated with specific resources. In addition to service-specific condition keys, Alibaba Cloud provides a set of common condition keys applicable across all RAM-supported services.

  • Dependent action: The dependent actions required to run the action. To complete the action, the RAM user or the RAM role must have the permissions to perform all dependent actions.

Action

Access level

Resource type

Condition key

Dependent action

sr:ModifyNodeNumber

get

*Instance

acs:sr:{#regionId}:{#accountId}:instance/{#InstanceId}

None None

Request syntax

POST /webapi/resourceChange/modifyNodeNumber HTTP/1.1

Request parameters

Parameter

Type

Required

Description

Example

InstanceId

string

Yes

The instance ID.

c-b25e21e24388****

NodeGroupId

string

Yes

The compute group ID.

ng-3d5ce6454354****

Target

integer

Yes

The target number of nodes.

3

PromotionOptionNo

string

No

The coupon ID.

youhuiquan_promotion_option_id_for_blank

Parallelism

integer

No

The decommission concurrency for BE scale-in scenarios in compute-storage decoupled architecture. Default value: 1.

1

TerminationGracePeriodSeconds

integer

No

The duration to wait for running tasks to complete before dropping nodes during CN scale-in scenarios in storage-compute disaggregation architecture.

60

Response elements

Element

Type

Description

Example

object

HttpStatusCode

integer

The HTTP status code.

200

RequestId

string

The request ID.

32A44F0D-BFF6-5664-999A-218BBDE7****

Success

boolean

Indicates whether the request was successful.

false

ErrCode

string

The error code.

InvalidParams

ErrMessage

string

The error message.

Invalid params: [instance not exists].

Data

integer

The order ID.

24151320976****

AccessDeniedDetail

string

The details of the permission verification failure.

{ "PolicyType": "AccountLevelIdentityBasedPolicy", "AuthPrincipalOwnerId": "xxx", "EncodedDiagnosticMessage": "xxx", "AuthPrincipalType": "xxx", "AuthPrincipalDisplayName": "xxx", "NoPermissionType": "ImplicitDeny", "AuthAction": "sr:xxx" }

Examples

Success response

JSON format

{
  "HttpStatusCode": 200,
  "RequestId": "32A44F0D-BFF6-5664-999A-218BBDE7****",
  "Success": false,
  "ErrCode": "InvalidParams",
  "ErrMessage": "Invalid params: [instance not exists].",
  "Data": 0,
  "AccessDeniedDetail": "{     \"PolicyType\": \"AccountLevelIdentityBasedPolicy\",     \"AuthPrincipalOwnerId\": \"xxx\",     \"EncodedDiagnosticMessage\": \"xxx\",     \"AuthPrincipalType\": \"xxx\",     \"AuthPrincipalDisplayName\": \"xxx\",     \"NoPermissionType\": \"ImplicitDeny\",     \"AuthAction\": \"sr:xxx\"   }"
}

Error codes

See Error Codes for a complete list.

Release notes

See Release Notes for a complete list.