• Elastic Load Balancing

elb
  1. Help Center
  2. Elastic Load Balancing
  3. API Reference
  4. Enhanced Load Balancer APIs
  5. Pool (Backend Server Group)
  6. Modifying a Backend Server Group

Modifying a Backend Server Group

Function

This API is used to modify a backend server group.

URI

PUT /v2.0/lbaas/pools/{pool_id}

Table 1 Parameter description

Parameter

Type

Mandatory

Description

pool_id

Uuid

Yes

Specifies the backend server group ID.

Constraints

If the provisioning status of the load balancer associated with a backend server group is not ACTIVE, the backend server group cannot be updated.

Request

Table 2 Parameter description

Parameter

Type

Mandatory

Description

pool

Dict

Yes

Specifies the backend server group. For details, see Table 3.

Table 3 pool field description

Parameter

Type

Mandatory

Description

name

String (255)

No

Specifies the backend server group name.

description

String (255)

No

Provides supplementary information about the backend server group.

lb_algorithm

String

No

Specifies the load balancing algorithm of the backend server group.

Optional values are as follows:
  • ROUND_ROBIN: indicates the weighted round robin algorithm.
  • LEAST_CONNECTIONS: indicates the weighted least connection algorithm.
  • SOURCE_IP: indicates the source IP hash algorithm.

When the value is SOURCE_IP, the weights of backend servers in the server group are invalid.

admin_state_up

Bool

No

Specifies the administrative status of the backend server group.

This parameter is reserved and has been not used. The default value is true.

session_persistence

Dict

No

Specifies whether to enable the sticky session feature. For details, see Table 7.

Once the sticky session feature is enabled, requests from the same client are sent to the same backend server within the specified period.

When this feature is disabled, the parameter value is null.

Table 4 session_persistence field description

Parameter

Type

Mandatory

Description

type

String

No

Specifies the sticky session type.

Optional values are as follows:
  • SOURCE_IP: Requests are distributed based on the source IP address. Requests from the same IP address are sent to the same backend server.
  • HTTP_COOKIE: When the client sends a request for the first time, the load balancer automatically generates a cookie and inserts the cookie into the response message. Subsequent requests are sent to the backend server that processes the first request.
  • APP_COOKIE: When the client sends a request for the first time, the backend server generates a cookie and inserts the cookie into the response message. Subsequent requests are sent to the backend server that processes the first request.
  • When the protocol of the backend server group is TCP, only SOURCE_IP takes effect. When the protocol of the backend server group is HTTP, HTTP_COOKIE and APP_COOKIE take effect.

cookie_name

String

No

Specifies the cookie name.

This parameter is mandatory and can be specified when the sticky session type is APP_COOKIE.

persistence_timeout

Int

No

Specifies the sticky session timeout duration.

This parameter is invalid when type is set to APP_COOKIE.

Optional value ranges are as follows:
  • When the protocol of the backend server is TCP or UDP, the value ranges from 1 to 60.
  • When the protocol of the backend server is HTTP, the value ranges from 1 to 1440.

Response

Table 5 Parameter description

Parameter

Type

Description

pool

Dict

Specifies the backend server group. For details, see Table 6.

Table 6 pools field description

Parameter

Type

Description

id

Uuid

Specifies the backend server group ID.

tenant_id

String (255)

Specifies the ID of the project where the backend server group is used.

name

String (255)

Specifies the backend server group name.

description

String (255)

Provides supplementary information about the backend server group.

protocol

String

Specifies the protocol that the backend server group uses to receive requests.

TCP, UDP, and HTTP are supported.

When a backend server group is added with the listener ID specified, the relationships between the backend server group protocol and the listener protocol are as follows:

  • When the listener protocol is UDP, the backend server group protocol must be UDP.
  • If the listener protocol is TCP, the backend server group protocol must be TCP.
  • If the listener protocol is HTTP or TERMINATED_HTTPS, the backend server group protocol must be HTTP.

lb_algorithm

String

Specifies the load balancing algorithm of the backend server group.

The value can be one of the following:
  • ROUND_ROBIN: indicates the weighted round robin algorithm.
  • LEAST_CONNECTIONS: indicates the weighted least connection algorithm.
  • SOURCE_IP: indicates the source IP hash algorithm. When the value is SOURCE_IP, the weights of backend servers in the server group are invalid.

members

List

Lists the IDs of backend servers in the backend server group.

healthmonitor_id

Uuid

Specifies the ID of the health check configured for the backend server group.

admin_state_up

Bool

Specifies the administrative status of the backend server group.

This parameter is reserved and has been not used. The default value is true.

listeners

List

Lists the IDs of listeners associated with the backend server group.

loadbalancers

List

Lists the IDs of load balancers associated with the backend server group.

session_persistence

Dict

Specifies whether to enable the sticky session feature. For details, see Table 6.

Once the sticky session feature is enabled, requests from the same client are sent to the same backend server within the specified period.

When this feature is disabled, the parameter value is null.

Table 7 session_persistence field description

Parameter

Type

Description

type

String

Specifies the sticky session type.

The value can be one of the following:
  • SOURCE_IP: Requests are distributed based on the source IP address. Requests from the same IP address are sent to the same backend server.
  • HTTP_COOKIE: When the client sends a request for the first time, the load balancer automatically generates a cookie and inserts the cookie into the response message. Subsequent requests are sent to the backend server that processes the first request.
  • APP_COOKIE: When the client sends a request for the first time, the backend server generates a cookie and inserts the cookie into the response message. Subsequent requests are sent to the backend server that processes the first request.

When the protocol of the backend server group is TCP, only SOURCE_IP takes effect. When the protocol of the backend server group is HTTP, HTTP_COOKIE and APP_COOKIE take effect.

cookie_name

String

Specifies the cookie name.

This parameter is mandatory when the sticky session type is APP_COOKIE.

persistence_timeout

Int

Specifies the sticky session timeout duration.

This parameter is invalid when type is set to APP_COOKIE.

  • Optional value ranges are as follows:
    • When the protocol of the backend server is TCP or UDP, the value ranges from 1 to 60.
    • When the protocol of the backend server is HTTP, the value ranges from 1 to 1440.

Example

  • Example request 1: Updating a backend server group
    PUT https://{Endpoint}/v2.0/lbaas/pools/12ff63af-4127-4074-a251-bcb2ecc53ebe 
    
    { 
        "pool": { 
            "name": "pool2", 
            "description": "pool two", 
            "lb_algorithm": "LEAST_CONNECTIONS" 
        } 
    }
  • Example response 1
    {
        "pool": {
            "lb_algorithm": "LEAST_CONNECTIONS",
            "protocol": "HTTP",
            "description": "pool two",
            "loadbalancers": [
                {
                    "id": "63ad9dfe-4750-479f-9630-ada43ccc8117"
                }
            ],
            "admin_state_up": true,
            "tenant_id": "1a3e005cf9ce40308c900bcb08e5320c",
            
            "session_persistence": {
                "cookie_name": null,
                "type": "HTTP_COOKIE",
                "persistence_timeout": 1
            },
            "healthmonitor_id": null,
            "listeners": [
                {
                    "id": "39de4d56-d663-46e5-85a1-5b9d5fa17829"
                }
            ],
            "members": [],
            "id": "12ff63af-4127-4074-a251-bcb2ecc53ebe",
            "name": "pool2"
        }
    }
  • Example request 2: Disabling the sticky session feature of a backend server group
    PUT https://{Endpoint}/v2.0/lbaas/pools/d46eab56-d76b-4cd3-8952-3c3c4cf113aa
    
    {
        "pool": {
            "session_persistence":null
        }
    }
  • Example response 2
    {
        "pool": {
            "lb_algorithm": "ROUND_ROBIN",
            "protocol": "HTTP",
            "description": "",
            "admin_state_up": true,
            "loadbalancers": [
                {
                    "id": "63ad9dfe-4750-479f-9630-ada43ccc8117"
                }
            ],
            "tenant_id": "601240b9c5c94059b63d484c92cfe308",
            
            "session_persistence": null,
            "healthmonitor_id": null,
            "listeners": [],
            "members": [],
            "id": "d46eab56-d76b-4cd3-8952-3c3c4cf113aa",
            "name": ""
        }
    }

Response Codes

For details, see HTTP Status Codes for Enhanced Load Balancers.