Parameter | Description |
Select Listener Protocol | Select a listener protocol. In this example, HTTPS is selected. |
Backend Protocol | In this example, an HTTPS listener is used. Backend Protocol is automatically set to HTTP and cannot be changed. |
Listener Port | Specify the listening port to receive and forward requests to backend servers. Valid values: 1 to 65535. |
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. Default value: Round Robin (RR). 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.
For more information about the scheduling algorithm and the applicable scenarios, see SLB scheduling algorithms. |
Session Persistence | By default, session persistence is disabled. After session persistence is enabled, CLB forwards all requests that are from the same client to the same backend server. Cookie Option: 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. Session Persistence Timeout Period: If you select Insert Cookie, specify a timeout period for session persistence. Rewrite cookie: If you select this option, you can 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.
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Enable HTTP/2 | By default, HTTP/2 is enabled. HTTP/2 provides the multiplexing feature. If a listener of a CLB instance supports the HTTP/2 protocol, the instance can use a single TCP connection to forward multiple HTTP requests and responses, which greatly enhances the transmission speed. |
Access Control | Specify whether to enable access control. By default, access control is disabled. 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 Specified IP Addresses to Access the SLB Instance. 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: Forbids Specified IP Addresses to Access the SLB Instance. 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. Whitelist: 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: 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 network ACLs, and IPv4 instances can be associated only with IPv4 network ACLs. For more information about how to create a network ACL, see Create a network ACL. |
Bandwidth Throttling for Listeners | If a pay-by-bandwidth CLB instance is used, you can set a maximum bandwidth for 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 an SLB instance cannot exceed the maximum bandwidth of the SLB instance. By default, this feature is disabled and all listeners share the bandwidth of the CLB instance. For more information about how the listeners of a CLB instance can share the bandwidth of the CLB instance, see Enable bandwidth sharing among listeners of a 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.
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Idle Connection Timeout Period | The maximum duration for which the TCP connection between a CLB instance and a client can remain open without data transmission. Default value: 1 to 60. Unit: seconds. If no request is received within the specified timeout period, CLB closes the connection. When another request is received, CLB establishes a new connection. Note This timeout period applies to all servers group associated with the listener. If you want to specify another timeout period for a specific backend server, create a separate listener for this backend server and set the timeout period that you want. |
Connection Request Timeout | If no response is received from the backend server within the request timeout period, CLB returns the HTTP 504 error code to the client. Default value: 1 to 180. Unit: seconds. |
Gzip Compression | If you enable GZIP compression, files of specific types are compressed. If you disable GZIP compression, no file is compressed. By default, data compression is enabled for Gzip. 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. If more than one IP address is preserved, the first one is the client IP address. For detailed configuration, see Enable Layer 7 listeners to preserve client IP addresses. 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.
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Client IP Address Preservation | Specify whether to obtain client IP addresses. By default, this feature is enabled. |
Automatically Enable Listener | Specify whether to immediately enable the listener after it is created. By default, listeners are enabled after they are created. |
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