CDN:Configure the default origin host

How the origin host works

When a CDN edge node fetches content from your origin server, it includes a Host header in the HTTP request. The origin server uses this Host header to determine which website or application should handle the request.

Virtual hosting allows a single web server to host multiple websites, distinguished by the Host header value. For example, if you have multiple accelerated domain names that each accelerate different static resources, virtual hosting lets you consolidate them onto a single origin server instead of maintaining separate servers for each domain.

The following figure shows how virtual hosting works with multiple websites on one server.

NGINX example

NGINX implements virtual hosting through server blocks. Each block uses the server_name directive to match the Host header value from incoming requests:

server {
    listen      80;
    server_name example.org www.example.org;
    ...
}

server {
    listen      80;
    server_name example.net www.example.net;
    ...
}

server {
    listen      80;
    server_name example.com www.example.com;
    ...
}

In this configuration, three virtual websites are defined: example.org, example.net, and example.com. NGINX uses the server_name and the Host header value from the HTTP request to determine which virtual website to serve. If no virtual website matches, NGINX uses the default one. If no default is configured, the first server block is used.

When you access a URL without specifying the Host header, the Host header value defaults to the host and port in the URL. However, Alibaba Cloud CDN sets the Host header to the accelerated domain name by default. The default origin host feature lets you override this value, which is essential when your origin server uses virtual hosting.

Choose a domain type

The Domain Type parameter determines the Host header value in back-to-origin requests. Choose based on your origin server setup:

Procedure

1. Log on to the CDN console.

2. In the left navigation pane, click Domain Names.

3. On the Domain Names page, find the target domain name and click Manage in the Actions column.

4. In the domain's navigation pane, click Origin Fetch.

5. In the Default Origin Host section, click Modify.

6. Turn on Origin Host and configure the Domain Type parameter.

   

7. Click OK.

Examples