Server Load Balancer:Add an HTTP listener

Step 1: Create a listener

1. Log on to the CLB console.

2. Select the region where the CLB instance is deployed.

3. Use one of the following methods to open the listener configuration wizard:

   • On the Instances page, find the CLB instance that you want to manage and click Configure Listener in the Actions column.

   • On the Instances page, click the ID of the CLB instance that you want to manage. On the Listener tab, click Add Listener.

4. Configure the following parameters and click Next.

   Parameter	Description
   Listener Protocol	Select a listener protocol. In this example, HTTP is selected.
   Backend Protocol	In this example, an HTTP listener is created. Backend Protocol is set to HTTP.
   Listener Port	Specify the listener port that is used to receive and forward requests to backend servers. Valid values: 1 to 65535. By default, HTTP uses port 80.
   Listener Name	Specify a name for the listener.
   Tag	Select or enter a tag key and a tag value.
   Advanced Settings	Click Modify to configure advanced settings.
   Scheduling Algorithm	Select a scheduling algorithm. Weighted Round-Robin (WRR): Backend servers that have higher weights receive more requests than backend servers that have lower weights. Round-Robin (RR): Requests are distributed to backend servers in sequence.
   Redirection	Specify whether to redirect traffic from the HTTP listener to an HTTPS listener. To enable traffic redirection, you must also select an HTTPS listener. Note Before you enable traffic redirection, make sure that an HTTPS listener is created. For more information, see Redirect requests from HTTP to HTTPS.
   Session Persistence	Specify whether to enable session persistence. After the session persistence feature is enabled, the CLB instance distributes requests that are from the same client to the same backend server. CLB enables persistence of HTTP sessions based on cookies. Cookie Options: Insert cookie: If you select this option, you need to only specify the timeout period of the cookie. CLB inserts a cookie (SERVERID) into the first HTTP or HTTPS response that is sent to a client. The next request from the client contains the cookie, and the listener forwards the request to the recorded backend server. Persistent Timeout: If you select Insert cookie, specify a timeout period for session persistence. Rewrite cookie: If you select this option, you must specify the cookie that you want to insert into an HTTP or HTTPS response. In this case, you must specify the timeout period and lifetime of the cookie on a backend server. After you specify a cookie, CLB overwrites the original cookie with the specified cookie. The next time CLB receives a client request that contains the specified cookie, the listener distributes the request to the recorded backend server. Cookie Name: If you select Rewrite cookie, you must specify a name for the cookie.
   Access Control	Specify whether to enable access control. Select an access control method after you enable access control. Then, select an access control list (ACL) as the whitelist or blacklist of the listener. Whitelist: allows access from specific IP addresses. Only requests from the IP addresses or CIDR blocks specified in the network ACL are forwarded. Whitelists apply to scenarios in which you want to allow access only from specific IP addresses. Your service may be adversely affected if the whitelist is not properly configured. After a whitelist is configured, only requests from IP addresses that are added to the whitelist are forwarded by the listener. If a whitelist is configured but no IP address is added to the whitelist, the listener forwards all requests. Blacklist: denies access from specific IP addresses. Requests from the IP addresses or CIDR blocks specified in the network ACL are denied. Blacklists apply to scenarios in which you want to deny access from specific IP addresses. If a blacklist is configured but no IP address is added to the blacklist, the listener forwards all requests. Note IPv6 instances can be associated only with IPv6 ACLs. IPv4 instances can be associated only with IPv4 ACLs. For more information, see Create an ACL.
   Enable Peak Bandwidth Limit	Specify whether to set a maximum bandwidth for the listener. If a pay-by-bandwidth CLB instance is used, you can set the maximum bandwidth of each listener to limit the amount of network traffic forwarded by listeners. The sum of the maximum bandwidth of all listeners that are added to a CLB instance cannot exceed the maximum bandwidth of the CLB instance. By default, this feature is disabled and all listeners share the bandwidth of the CLB instance. Important For example, the maximum bandwidth of an Internet-facing CLB instance is 5 Mbit/s, and you configure two listeners. You allocate 5 Mbit/s of bandwidth to Listener A, and do not allocate bandwidth to Listener B. In this case, Listener B is inaccessible. Exercise caution when you allocate bandwidth. If three listeners are configured for an internal-facing CLB instance, and the total bandwidth allocated to Listener A and Listener B is 5,120 Mbit/s, Listener C is inaccessible. Exercise caution when you allocate bandwidth. If a pay-by-data-transfer CLB instance is used, the bandwidth of listeners is unlimited by default.
   Idle Connection Timeout Period	Specify the timeout period of an idle connection. If no request is received within the specified timeout period, CLB closes the connection. When a request is received, CLB establishes a new connection.
   Connection Request Timeout	Specify the timeout period of a request. If no response is received from a backend server within the specified timeout period, CLB returns the HTTP 504 status code to the client.
   GZIP Compression	If you enable GZIP compression, files of specific types are compressed. If you disable GZIP compression, no file is compressed. GZIP supports the following file types: text/xml, text/plain, text/css, application/javascript, application/x-javascript, application/rss+xml, application/atom+xml, and application/xml.
   Custom HTTP Header	Select the HTTP headers that you want to add. Valid values: X-Forwarded-For: Retrieve Client IP: obtains client IP addresses. Note By default, Layer 7 listeners of CLB use the X-Forwarded-For header to preserve client IP addresses. The header cannot be disabled. SLB-ID: Retrieve SLB ID: obtains the ID of the CLB instance. SLB-IP: Retrieve SLB IP: obtains the IP address of the CLB instance. X-Forwarded-Proto: Retrieve Listener Protocol: obtains the listener protocol.
   Client IP Address Preservation	This feature retrieves client IP addresses and is enabled by default.
   Automatically Enable Listener	Specify whether to immediately enable the listener after it is created. By default, listeners are enabled after they are created.

Step 2: Add backend servers

After the listener is created, you must add backend servers to process client requests. You can use the default server group that is configured for the CLB instance. You can also create a vServer group. For more information, see Backend server overview.

In this example, backend servers are added to the default server group.

1. In the Backend Servers step, select Default Server Group and click Add More.

2. In the Servers panel, select the backend servers that you want to add and click Next.

3. In the Weight column, configure the weights of the backend servers.

   Note

   • An Elastic Compute Service (ECS) instance with a higher weight receives more requests. The default weight is 100. You can click Reset to set Weight to the default value.

   • If the weight of a backend server is set to 0, no request is distributed to the backend server.

4. Click Add. On the Default Server Group tab, specify the ports that you want to open on the backend servers to receive requests. Click Next.

   You can specify the same port for backend servers that are added to the same CLB instance.

Step 3: Configure health checks

1. Optional. In the Health Check step, click Modify to modify the health check configurations.

   For more information, see Configure and manage CLB health checks.

2. Click Next.

Step 4: Submit the configurations

1. In the Confirm step, check the configurations of the listener. You can click Modify to modify the configurations.

2. Confirm the configurations and click Submit.

3. After Configuration Successful appears, click OK.

   After you configure the listener, you can view the listener on the Listener tab.