Adding an HTTP Listener

Scenarios

HTTP listeners are suitable for applications that require identifying the data content, such as web applications and small mobile games.

Constraints

If the listener protocol is HTTP, the protocol of the backend server group is HTTP by default and cannot be changed.
If you only select network load balancing (TCP/UDP) for your dedicated load balancer, you cannot add an HTTP listener to this load balancer.

Adding an HTTP Listener to a Dedicated Load Balancer

Log in to the management console.
In the upper left corner of the page, click and select the desired region and project.
Hover on in the upper left corner to display Service List and choose Network > Elastic Load Balance.
Locate the load balancer and click its name.

Under Listeners, click Add Listener. Configure the parameters based on Table 1.

**Table 1** Parameters for configuring a listener
Parameter	Description	Example Value
Name	Specifies the listener name.	listener
Frontend Protocol	Specifies the protocol that will be used by the load balancer to receive requests from clients.	HTTP
Frontend Port	Specifies the port that will be used by the load balancer to receive requests from clients. The port number ranges from 1 to 65535.	80
Redirect	Specifies whether to enable redirection. If you have both HTTPS and HTTP listeners, you can use this function to redirect the requests from the HTTP listener to the HTTPS listener to ensure security.	N/A
Redirected To	Specifies the HTTPS listener to which requests are redirected if Redirect is enabled.	listener_HTTPS_443
Access Control	Specifies how access to the listener is controlled. For details, see Access Control. The following options are available: All IP addresses Blacklist Whitelist	Blacklist
IP Address Group	Specifies the IP address group associated with a whitelist or blacklist. If there is no IP address group, create one first. For more information, see Creating an IP Address Group.	ipGroup
Transfer Client IP Address	Specifies whether to transmit IP addresses of the clients to backend servers. This function is enabled for dedicated load balancers by default and cannot be disabled.	Enabled
Advanced Settings
Transfer Load Balancer EIP	Specifies whether to store the EIP bound to the load balancer in the X-Forwarded-ELB-IP header field and pass this field to backend servers.	N/A
Transfer Listener Port Number	Specifies whether to store the port number used by the listener in the X-Forwarded-Port header field and pass the field to backend servers.	N/A
Transfer Port Number in the Request	Specifies whether to store the port number used by the client in the X-Forwarded-For-Port header field and pass the field to backend servers.	N/A
Rewrite X-Forwarded-Host	If you disable this option, the load balancer passes the X-Forwarded-Host field to backend servers. If you enable this option, the load balancer rewrites the X-Forwarded-Host field based on the Host field in the request header sent from the client and sends the rewritten X-Forwarded-Host field to backend servers.	N/A
Idle Timeout	Specifies the length of time for a connection to keep alive, in seconds. If no request is received within this period, the load balancer closes the connection and establishes a new one with the client when the next request arrives. The idle timeout duration ranges from 0 to 4000.	60
Request Timeout	Specifies the length of time (in seconds) after which the load balancer closes the connection if the load balancer does not receive a request from the client. The request timeout duration ranges from 1 to 300.	60
Response Timeout	Specifies the length of time (in seconds) after which the load balancer sends a 504 Gateway Timeout error to the client if the load balancer receives no response from the backend server after routing a request to the backend server and receives no response after attempting to route the same request to other backend servers. The response timeout duration ranges from 1 to 300. NOTE: If you have enabled sticky sessions and the backend server does not respond within the response timeout duration, the load balancer returns 504 Gateway Timeout to the clients.	60
Description	Provides supplementary information about the listener. You can enter a maximum of 255 characters.	N/A

Click Next: Configure Request Routing Policy.

You are advised to select an existing backend server group.
You can also click Create new to create a backend server group and configure parameters as described in Table 2.

**Table 2** Parameters for configuring a backend server group
Parameter	Description	Example Value
Backend Server Group	Specifies a group of servers with the same features to receive requests from the load balancer. Two options are available: Create new Use existing NOTE: The backend protocol of the backend server group must match the frontend protocol. For example, if the frontend protocol is TCP, the backend protocol must be TCP.	Create new
Backend Server Group Name	Specifies the name of the backend server group.	server_group
Backend Protocol	Specifies the protocol that will be used by backend servers to receive requests. The backend protocol is HTTP by default and cannot be changed.	HTTP
Load Balancing Algorithm	Specifies the algorithm that will be used by the load balancer to distribute traffic. The following options are available: Weighted round robin: Requests are routed to different servers based on their weights, which indicate server processing performance. Backend servers with higher weights receive proportionately more requests, whereas equal-weighted servers receive the same number of requests. Weighted least connections: In addition to the number of active connections established with each backend server, each server is assigned a weight based on their processing capability. Requests are routed to the server with the lowest connections-to-weight ratio. Source IP hash: The source IP address of each request is calculated using the consistent hashing algorithm to obtain a unique hash key, and all backend servers are numbered. The generated key is used to allocate the client to a particular server. This allows requests from different clients to be routed based on source IP addresses and ensures that a client is directed to the same server that it was using previously. NOTE: Choose an appropriate algorithm based on your requirements for better traffic distribution. For Weighted round robin or Weighted least connections, no requests will be routed to a server with a weight of 0.	Weighted round robin
Sticky Session	Specifies whether to enable sticky sessions. If you enable sticky sessions, all requests from a client during one session are sent to the same backend server. This parameter is optional and can be enabled if you have selected Weighted round robin for Load Balancing Algorithm.	N/A
Sticky Session Type	Specifies the type of sticky sessions for HTTP and HTTPS listeners. Load balancer cookie: The load balancer generates a cookie after receiving a request from the client. All subsequent requests with the same cookie are then routed to the same backend server. NOTE:	Load balancer cookie
Slow Start	Specifies whether to enable slow start, which is disabled by default. After you enable slow start, the load balancer linearly increases the proportion of requests to send to backend servers in this mode. When the slow start duration elapses, the load balancer sends full share of requests to backend servers and exits the slow start mode. For details, see Slow Start (Dedicated Load Balancers).	N/A
Slow Start Duration	Specifies the slow start duration if Slow Start is enabled. The duration ranges from 30 to 1200, in seconds, and the default value is 30.	30
Description	Provides supplementary information about the backend server group. You can enter a maximum of 255 characters.	N/A

Click Next: Add Backend Server. Add backend servers and configure health check for the backend server group. For details about how to add backend servers, see Overview. For the parameters required for configuring a health check, see Table 3.

**Table 3** Parameters for configuring a health check
Parameter	Description	Example Value
Health Check	Specifies whether to enable health checks. If the health check is enabled, click next to Advanced Settings to set health check parameters.	N/A
Health Check Protocol	Specifies the protocol that will be used by the load balancer to check the health of backend servers. If the backend protocol is HTTP or HTTPS, the health check protocol can be TCP, HTTP, or HTTPS.	HTTP
Domain Name	Specifies the domain name that will be used for health checks. This parameter is mandatory if the health check protocol is HTTP or HTTPS. You can use the private IP address of the backend server as the domain name. You can also specify a domain name that consists of at least two labels separated by periods (.). Use only letters, digits, and hyphens (-). Do not start or end strings with a hyphen. Max total: 100 characters. Max label: 63 characters.	www.elb.com
Health Check Port	Specifies the port that will be used by the load balancer to check the health of backend servers. The port number ranges from 1 to 65535. NOTE: By default, the service port on each backend server is used. You can also specify a port for health checks.	80
Path	Specifies the health check URL, which is the destination on backend servers for health checks. This parameter is mandatory if the health check protocol is HTTP or HTTPS. The path can contain 1 to 80 characters and must start with a slash (/).	/index.html
Interval (s)	Specifies the interval for sending health check requests, in seconds. The interval ranges from 1 to 50.	5
Timeout (s)	Specifies the maximum time required for waiting for a response from the health check, in seconds. The timeout duration ranges from 1 to 50.	3
Maximum Retries	Specifies the maximum number of health check retries. The value ranges from 1 to 10.	3

Click Next: Confirm.
Confirm the configuration and click Submit.