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ENS:DescribeLoadBalancerTCPListenerAttribute

Last Updated:Mar 27, 2026

Queries the configurations of a Transmission Control Protocol (TCP) listener.

Operation description

  • up to 100 times per second per account.

  • up to 10 times per second per user.

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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

ens:DescribeLoadBalancerTCPListenerAttribute

get

*All Resource

*

None None

Request parameters

Parameter

Type

Required

Description

Example

ListenerPort

integer

Yes

The listening port that you want to query. Valid values: 1 to 65535.

80

LoadBalancerId

string

Yes

The ID of the ELB instance.

lb-5snthcyu1x10g7tywj7iu****

Response elements

Element

Type

Description

Example

object

Schema of Response

RequestId

string

The ID of the request.

473469C7-AA6F-4DC5-B3DB-A3DC0DE3C83E

ListenerPort

integer

The frontend port that is used by the ELB instance.

80

Status

string

The status of the listener. Valid values:

  • Running

  • Stopped

  • Starting

  • Configuring

  • Stopping

Stopped

Bandwidth

integer

The peak bandwidth of the Edge Load Balancer (ELB) instance. The default value is -1, which indicates that the bandwidth is not limited.

-1

Scheduler

string

The routing algorithm. Valid values:

  • wrr: Backend servers with higher weights receive more requests than those with lower weights.

  • wlc: Requests are distributed based on the weight and load of each backend server. The load refers to the number of connections to a backend server. If two backend servers have the same weight, the backend server that has fewer connections receives more requests.

  • rr: Requests are distributed to backend servers in sequence.

  • sch: consistent hashing that is based on source IP addresses. Requests from the same source IP address are distributed to the same backend server.

  • qch: consistent hashing that is based on QUIC connection IDs. Requests that contain the same QUIC connection ID are distributed to the same backend server.

  • iqch: consistent hashing that is based on specific three bytes of the iQUIC CIDs. Requests whose second to fourth bytes are the same are distributed to the same backend server.

wrr

PersistenceTimeout

integer

The timeout period of session persistence.

  • Default value: 0. If the default value is used, the system disables session persistence.

  • Valid values: 0 to 3600.

  • Unit: seconds.

0

EstablishedTimeout

integer

The timeout period of a connection. Valid values: 10 to 900. Unit: seconds.

500

HealthCheck

string

Indicates whether the health check feature is enabled. Valid values:

  • on

  • off

on

HealthyThreshold

integer

The number of consecutive successful health checks that must occur before an unhealthy and inaccessible backend server is declared healthy and accessible. Valid values: 2 to 10.

Note

This parameter is returned only if you set HealthCheck to on.

4

UnhealthyThreshold

integer

The number of consecutive failed health checks that must occur before a healthy and accessible backend server is declared unhealthy and inaccessible. Valid values: 2 to 10.

Note

This parameter is returned only if you set HealthCheck to on.

4

HealthCheckConnectTimeout

integer

The timeout period for a health check response. If a backend server does not respond within the specified timeout period, the server fails the health check.

  • Default value: 5.

  • Valid values: 1 to 300.

  • Unit: seconds.

Note
  • This parameter takes effect only if the HealthCheck parameter is set to on.

  • If the value of the HealthCheckTimeout property is smaller than the value of the HealthCheckInterval property, the timeout period specified by the HealthCheckTimeout property becomes invalid and the value of the HealthCheckInterval property is used as the timeout period.

100

HealthCheckInterval

integer

The interval at which health checks are performed. Valid values: 1 to 50. Unit: seconds.

5

Description

string

The name of the listener.

example

HealthCheckHttpCode

string

The HTTP status codes for a successful health check. Valid values:

  • http_2xx (default)

  • http_3xx

  • http_4xx

  • http_5xx

Note

This parameter is returned only if you set HealthCheck to on.

http_2xx

HealthCheckDomain

string

The domain name that is used for health checks.

Note

This parameter is returned only if you set HealthCheck to on.

example.com

HealthCheckURI

string

The URI used for health checks. The URI must be 1 to 80 characters in length.

Note
  • A URL must start with a forward slash (/) but cannot contain only forward slashes (/).

  • This parameter takes effect only if the HealthCheck parameter is set to on.

/example/index.html

HealthCheckType

string

The type of health checks. Valid values:

  • tcp (default)

  • http

tcp

BackendServerPort

integer

The port used by the backend server of the ELB instance. Valid values: 1 to 65535.

8080

HealthCheckConnectPort

integer

The port that is used for health checks. Valid values: 1 to 65535. If an empty string is returned for this parameter, the port specified by BackendServerPort is used for health checks.

Note

This parameter is returned only if you set HealthCheck to on.

8000

EipTransmit

string

Indicates whether EIP pass-through is enabled. Valid values:

  • on

  • off (default)

on

Examples

Success response

JSON format

{
  "RequestId": "473469C7-AA6F-4DC5-B3DB-A3DC0DE3C83E",
  "ListenerPort": 80,
  "Status": "Stopped",
  "Bandwidth": -1,
  "Scheduler": "wrr",
  "PersistenceTimeout": 0,
  "EstablishedTimeout": 500,
  "HealthCheck": "on",
  "HealthyThreshold": 4,
  "UnhealthyThreshold": 4,
  "HealthCheckConnectTimeout": 100,
  "HealthCheckInterval": 5,
  "Description": "example",
  "HealthCheckHttpCode": "http_2xx",
  "HealthCheckDomain": "example.com",
  "HealthCheckURI": "/example/index.html",
  "HealthCheckType": "tcp",
  "BackendServerPort": 8080,
  "HealthCheckConnectPort": 8000,
  "EipTransmit": "on"
}

Error codes

HTTP status code

Error code

Error message

Description

400 ens.interface.error An error occurred while call the API.
400 LoadBalancerNotFound The input parameter loadBalancerId that is not found.
400 ListenerNotFound Listener is not found. Listener does not exist
400 NoPermission Permission denied.
400 InvalidParameter.%s The specified field %s invalid. Please check it again.

See Error Codes for a complete list.

Release notes

See Release Notes for a complete list.