# Update the backend instance properties of the traditional load balancer - UpdateBackendAttribute

## Overview

Update the properties of CLB backend resource instances (service nodes)



 > ℹ️ The service node for message forwarding does not currently support modification of Port; BackendId corresponds to the BackendId returned by AllocateBackend or the BackendId in the ULBBackendSet structure returned by DescribeULB/DescribeVServer, which is the backend instance Id of the traditional load balancer.


## Definition

### Public Parameters

| Parameter Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **Action**     | string  | Corresponding API command name, the current API is `UpdateBackendAttribute`.                      | **Yes** |
| **PublicKey**  | string  | The user's public key can be obtained from [Console](https://console.scloudsg.com/uaccount/api_manage)                                             | **Yes** |
| **Signature**  | string  | User signature generated based on public key and API command, see [Signature Algorithm](/docs/api/summary/signature.md)  | **Yes** |

### Request Parameters

| Parameter Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **Region** | string | Region. See [List of Regions and Availability Zones](/docs/api/summary/regionlist) |**Yes**|
| **ProjectId** | string | Project ID. If not filled in, the default project is used, sub-accounts must be filled in. Please refer to the [GetProjectList interface](/docs/api/summary/get_project_list). |**Yes**|
| **ULBId** | string | Traditional Load Balancer Resource ID |**Yes**|
| **BackendId** | string | ID of the backend resource instance (CLB backend ID, not the resource's own ID) |**Yes**|
| **Port** | int | Backend resource service port, value range [1-65535] |No|
| **Weight** | int | The weight of the added backend RS (effective under the weighted round-robin algorithm), the value range is [1-100], the default is 1. |No|
| **Enabled** | int | Backend Instance Status Switch |No|
| **IsBackup** | int | Is it a backup?<br />0: Primary rs<br />1: Backup rs<br />Default is 0 |No|

### Response Field

| Field Name | Type | Description Information | Required |
|:---|:---|:---|:---|
| **RetCode** | int | Return status code. If it is 0, it means successful return. If it is not 0, it means failure. |**Yes**|
| **Action** | string | Operation command name. |**Yes**|
| **Message** | string | Returns an error message, providing detailed description when `RetCode` is non-zero. |No|




## Example

### Request Example
    
```
https://api.scloudsg.com/?Action=UpdateBackendAttribute
&Region=cn-bj2
&ProjectId=project-XXXX
&ULBId=ulb-XXXX
&BackendId=backend-XXXX
&Port=8080
&Enabled=0
&Weight=2
&IsBackup=0
```

### Response Example
    
```json
{
  "Action": "UpdateBackendAttributeResponse",
  "BackendSet": [
    {
      "BackendId": "VrjEOOfp",
      "SubMessage": "fHpUyKqK",
      "SubRetCode": 1
    }
  ],
  "RetCode": 0
}
```