Server Load Balancer:Add an HTTP listener

Procedure

This topic describes two procedures to show you how to create an HTTP listener. You can choose one as needed.

• Manual creation: You can create an HTTP listener and configure advanced features based on business requirements.

• Quick creation: You can use a template to quickly create an HTTP listener. You only need to specify a listener protocol, a listener port, and a backend server group.

Manual creation

1. Log on to the ALB console.

2. In the top navigation bar, select the region in which the ALB instance resides.

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

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

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

4. In the Configure Listener step, configure the parameters that are described in the following table, and click Next.

   Parameter	Description
   Listener Protocol	Select a listener protocol. In this example, HTTP is selected.
   Listener Port	Select the port on which the ALB instance listens. The ALB instance listens for requests on the specified port and then forwards the requests to backend servers. Valid values: 1 to 65535. In most cases, port 80 is used for HTTP and port 443 is used for HTTPS. Note On the same ALB instance, the ports of listeners that use the same protocol must be unique. HTTP listeners and HTTPS listeners must use different ports. In this example, port 80 is used.
   Listener Name	Enter a name for the listener.
   Tag	Configure the Tag Key and Tag Value parameters to add a tag. You can add one or more tags. After you specify tags, you can filter listeners by tag on the Listener tab.
   Advanced Settings	You can click Modify to configure the advanced settings.
   Idle Connection Timeout Period	Specify a timeout period for idle connections. Unit: seconds. Valid values: 1 to 60. To specify a longer timeout period, go to the Quota Center console. If no request is received within the specified timeout period, ALB closes the connection. When another request is received, ALB establishes a new connection. Note This feature is not available for HTTP/2 requests.
   Connection Request Timeout	Specify a request timeout period. Unit: seconds. Valid values: 1 to 180. To specify a longer timeout period, go to the Quota Center console. If no response is received from the backend server within the request timeout period, ALB returns an HTTP 504 error code to the client.
   Compression	If you enable compression, specific types of files are compressed. If you disable compression, no file is compressed. Brotli supports all file types. GZIP supports the following file types: text/xml, text/plain, text/css, application/javascript, application/x-javascript, application/rss+xml, application/atom+xml, application/xml, and application/json. Note If a client request allows both Brotli and GZIP compression, ALB will use Brotli compression which is more efficient. If a client request allows only GZIP compression, and at least one file is in a format not supported by GZIP, ALB will not compress any files.
   Retrieve Client IP	Specify whether to enable the ALB instance to retrieve client IP addresses from the X-Forwarded-For header. If you enable this feature, you must specify trusted IP addresses. If you set the trusted IP address list to 0.0.0.0/0, the ALB instance retrieves the leftmost IP address in the X-Forwarded-For header. The IP address is the source client IP address. If you set the trusted IP address list in the format of proxy1 IP;proxy2 IP;.., the ALB instance compares the IP addresses in the X-Forwarded-For header from right to left against the trusted IP address list. The first IP address that is not on the trusted IP address list is considered the source client IP address. Usage notes If the X-Forwarded-For header contains multiple IP addresses, such as X-Forwarded-For: <client-ip-address>, <proxy1>, <proxy2>, …, the leftmost IP address is the source client IP address. If you want to enable the matching based on source IP addresses and throttling based on QPS per client IP address features in ALB forwarding rules, you must turn on the Retrieve Client IP switch to allow the ALB instance to retrieve source client IP addresses from the X-Forwarded-For header. For more information, see Create a forwarding rule. Note Retrieve Client IP is supported only by standard and WAF-enabled ALB instances, but not by basic ALB instances.
   Add HTTP Header	You can select the following options: Select whether to use the X-Forwarded-For header to obtain client IP addresses. If you select Add X-Forwarded-For to preserve client IP addresses, ALB can add an X-Forwarded-For header to or remove the X-Forwarded-For header from the request before forwarding the request to a backend server. Add (default) If you choose Add, ALB adds the IP address of the last hop to the X-Forwarded-For header in the request before forwarding the request to a backend server. If the request does not contain the X-Forwarded-For header, ALB creates an X-Forwarded-For header whose value is the IP address of the last hop and adds the header to the request. The X-Forwarded-For header in the request may contain multiple IP addresses which are separated by commas (,). Remove If you choose Remove, ALB removes the X-Forwarded-For header from the request before forwarding the request to a backend server. If you do not select Add X-Forwarded-For to preserve client IP addresses, ALB does nothing about the X-Forwarded-For header in the request before forwarding the request to a backend server. Format: X-Forwarded-For: <client-ip-address>, <proxy1>, <proxy2>, … Click to see an example about the X-Forwarded-For header in the request that is received by the backend server. In this example, the IP address of the last hop is 127.0.0.1. Request description Sample request Select Add X-Forwarded-For to preserve client IP addresses Not select Add X-Forwarded-For to preserve client IP addresses Add Remove The request received by ALB does not contain the X-Forwarded-For header. GET /index.html HTTP/1.1 Host: example.com X-Forwarded-For: 127.0.0.1 The X-Forwarded-For header does not exist. The X-Forwarded-For header does not exist. The request received by ALB contains the X-Forwarded-For header and a client IP address. GET /index.html HTTP/1.1 Host: example.com X-Forwarded-For: 127.0.0.2 X-Forwarded-For: 127.0.0.2, 127.0.0.1 The X-Forwarded-For header does not exist. X-Forwarded-For: 127.0.0.2 The request received by ALB contains the X-Forwarded-For header and multiple client IP addresses. GET /index.html HTTP/1.1 Host: example.com X-Forwarded-For: 127.0.0.2, 127.0.0.3 X-Forwarded-For: 127.0.0.2, 127.0.0.3, 127.0.0.1 The X-Forwarded-For header does not exist. X-Forwarded-For: 127.0.0.2, 127.0.0.3 For more information about how to enable ALB to preserve client IP addresses, see Enable ALB to preserve client IP addresses. Add SLB-ID to preserve SLB instance IDs: Add the SLB-ID header to store the ID of the ALB instance. Add X-Forwarded-Proto to preserve listener protocols: Add the X-Forwarded-Proto header to store the listener protocol. Add X-Forwarded-Port to preserve SLB listener ports: Add the X-Forwarded-Port header to store the listener port. Add X-Forwarded-Host to preserve client domain names: Add the X-Forwarded-Host header to store the domain name of a client that accesses ALB. Add X-Forwarded-Client-srcport to preserve client ports: Add the X-Forwarded-Client-srcport header to store the client port. Note We recommend that you configure your backend servers to follow the HTTP standard – be case-insensitive when processing the request headers. The X-Forwarded-For header that is created and added to the request by ALB always starts with an uppercase "X." Except for X-Forwarded-For, for the headers mentioned above, ALB processes them following the rules described above. For other headers, ALB keeps them in their original form in the request.

5. In the Select Server Group step, select a server group, view the backend servers, and then click Next.

6. In the Confirm step, confirm the configurations and click Submit.

Quick creation

If you select this method, you need to only specify a listener protocol, a listener port, and a server group.

1. Log on to the ALB console.

2. In the top navigation bar, select the region in which the ALB instance resides.

3. On the Instances page, find the ALB instance that you want to manage and click its ID.

4. Click the Listener tab. On the Listener tab, click Quick Create Listener.

5. In the Quick Create Listener dialog box, configure the parameters and click OK. The following table describes the parameters.

   Parameter	Description
   Listener Protocol	Select a listener protocol. In this example, HTTP is selected.
   Listener Port	The frontend port that is used to receive and forward requests to backend servers. You can select a commonly used port, or enter a port number. Valid values: 1 to 65535.
   Resource Group	Select a resource group for the server group.
   Server Group	Select a backend Server Group type. And then based on the selected type, choose an existing server group with backend servers added, or create a new server group.

References

• ALB supports various advanced forwarding rules. For more information, see Manage forwarding rules for a listener.

• If you encounter an abnormal status code returned by ALB, refer to ALB status codes.

• If a health check issue persists, refer to Troubleshoot ALB health check issues.

• More References

  • Redirect HTTP requests to an HTTPS listener

  • Use the traffic mirroring feature to mirror production traffic to a staging environment

  • Use ALB to implement canary release