Enterprises often use multiple origin servers in their content delivery architecture to improve redundancy and ensure high availability. If an origin server fails, the CDN should seamlessly switch requests to another healthy origin to avoid disrupting the end-user experience.

Atomile provides Automatic Origin Failover and Zero-Downtime Failover switching to simplify this process and help ensure business continuity and uninterrupted content delivery.

Automatic Origin Failover

When multiple origin server IP addresses are configured for your website, Automatic Origin Failover detects when an origin server becomes unavailable due to failure or maintenance. If the origin returns a configured status code, such as 503 Service Unavailable, the CDN immediately retries the request using another available origin server.

By default, this rerouting takes effect on subsequent user requests. To enable immediate failover for the current request, enable Zero-Downtime Failover switching.

Zero-Downtime Failover

The Zero-Downtime Failover feature immediately switches the current user request to another healthy origin server when a failure occurs, with no visible interruption. This helps maintain service availability and protects the user experience during origin server downtime.

How to Configure Automatic Origin Failover

1. Log in to the Atomile Console and select the appropriate product.
2. Go to Configuration, locate the domain you want to configure, and click Edit Configuration at the top, or click the Edit button to the right of the domain.
3. On the Edit Configuration page, find Origin Settings > Origin Failover, and then click Edit.
4. Select On from the Origin Failover drop-down list, and specify the status codes that trigger failover, separated by ;, for example, 502;503.

With this configuration, Atomile monitors origin responses. If the response contains an error status code from your configured list, the system automatically resolves another origin server IP address and retries the request.

After entering the status codes, click OK, and then click Next to submit your settings. To minimize potential disruption to your production environment, we strongly recommend performing a Pre-deploy test in a staging environment. This important step ensures that your configuration is correct before it goes live.

After you confirm that the settings are correct, click Deploy Now to apply them in the live environment. The configuration typically takes effect within 3 to 5 minutes. For more information about pre-deployment testing and validation, refer to Deploy the Configurations to Staging Environment for Validation.

How to Configure Zero-Downtime Failover

1. Log in to the Atomile Console and select the appropriate product.
2. Go to Configuration, locate the domain you want to configure, and click Edit Configuration at the top, or click the Edit button to the right of the domain.
3. On the Edit Configuration page, find Origin Settings > Zero-Downtime Failover, and enable the feature.
4. After enabling it, click Next to submit your configuration. Again, we recommend performing a Pre-deploy test in a staging environment before applying the configuration to production by clicking Deploy Now. For more information about pre-deployment testing, refer to Deploy the Configurations to Staging Environment for Validation.

Best Practices

Example: Automatic Origin Failover

Suppose you have configured three origin server IP addresses: 1.1.1.1, 2.2.2.2, and 3.3.3.3, and you want user requests to be automatically retried on another origin server when specific error status codes, such as 404 or 503, are returned.

1. If the initial origin request to 1.1.1.1 returns status code 503, Origin Failover is triggered.
2. The CDN selects an untried origin server IP from the configured list, for example, 2.2.2.2, and retries the request.
3. If the newly selected origin server returns status code 403, the CDN returns 403 directly to the user, because 403 is not included in the retry criteria.
4. If status code 503 is returned again, the CDN retries the request using the next origin server IP, 3.3.3.3.
5. If the final origin server also returns status code 503 and no other origin servers are available, the CDN returns 503 to the user and the process ends.

Notes

• Automatic Origin Failover is triggered only when a CDN edge server successfully connects to the origin server and receives a response status code. If the edge server cannot connect to the origin and no status code is returned, the default origin timeout retry mechanism is used instead.
• Zero-Downtime Failover works together with Automatic Origin Failover and requires Automatic Origin Failover to be enabled first.