How to force nginx to resolve DNS (of a dynamic hostname) every time when doing proxy_pass?

By default, Nginx caches DNS records for a certain period to enhance performance. However, if you have a dynamic hostname and you need Nginx to resolve DNS every time a request comes in, you can use the resolver and set directives in the Nginx configuration.

Here's an example of how you can force Nginx to resolve the DNS of a dynamic hostname for each request:

http {
    resolver <DNS_IP> valid=30s;  # Replace <DNS_IP> with your DNS server IP

    server {
        listen 80;

        location / {
            resolver <DNS_IP> valid=30s;  # Replace <DNS_IP> with your DNS server IP
            set $backend "your_dynamic_hostname";  # Replace with your dynamic hostname variable

            proxy_pass <http://$backend>;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
        }
    }
}

Explanation:

• The resolver directive specifies the DNS server Nginx should use to resolve domain names.
• The valid parameter in the resolver directive sets the time limit for caching DNS records. In this example, it's set to 30 seconds, meaning DNS records will expire and be re-resolved every 30 seconds.
• The set directive is used to create a variable ($backend) that holds your dynamic hostname.

This configuration tells Nginx to resolve the DNS for the dynamic hostname every 30 seconds and pass the requests to the resolved IP.

Remember to replace <DNS_IP> with the IP address of your DNS server and "your_dynamic_hostname" with the variable holding your actual dynamic hostname.

Please be cautious with the low caching time, as it might affect the server's performance due to frequent DNS lookups. Adjust the valid parameter as needed for your use case.

Got an article suggestion? Let us know

Explore more

Nginx

Remove "www" and redirect to "https" with nginx

Questions

How can I use environment variables in Nginx.conf

Questions

How to set up Nginx as a caching reverse proxy?

Questions

How to generate a private key for the existing .crt file on Nginx?

Unfortunately, this is not possible. You cannot generate a private key out of an existing certificate. If it would be possible, you would be able to impersonate virtually any HTTPS webserver.

Questions

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.