Intermittent blank or incomplete pages served via CDN after AEM Publish instance restart
If you restart an Adobe Experience Manager (AEM) Publish instance or add it to the load balancer before it is fully initialized, it can send blank or partially rendered pages to visitors through a CDN. To resolve the issue, remove the instance from the load balancer until it is fully initialized, restart it, verify its responses, and purge the affected pages from the CDN cache.
Description description
When an AEM Publish instance is restarted or newly added to the load balancer, it may begin serving requests before all rendering dependencies are fully initialized. This can result in incomplete HTML responses (such as blank or partially rendered pages) being sent to site visitors. If a CDN is in use, these incomplete responses are cached and served to subsequent visitors, causing the issue to persist until the cache is cleared.
Environment
- Adobe Experience Manager (AEM) (all versions)
- CDN integration (e.g., Akamai)
Symptoms
- Blank or partially rendered pages intermittently appear when accessing affected site URLs.
- The HTTP response returns status
200 OK, but the response body is truncated or missing expected content. - The CDN caches the incomplete response and serves it to other visitors.
Cause
A recently started AEM Publish instance began serving traffic before its rendering dependencies (such as OSGi bundles, script cache, or JCR session state) were fully initialized, resulting in incomplete HTML responses. The CDN cached these truncated responses, causing persistent blank pages until the cache was purged and the instance was restarted.
Resolution resolution
Follow the steps below to resolve the issue.
- Identify any AEM Publish instance that was recently restarted or added to the load balancer pool.
- Remove the affected Publish instance from receiving production traffic (for example, by taking it out of the load balancer pool) until it is fully initialized and all rendering dependencies are warmed up.
- Restart the affected Publish instance to ensure it is in a healthy, fully initialized state.
- After the instance has restarted, verify that it serves complete and correct page responses by accessing affected site URLs directly (bypassing the CDN if possible).
- Once you have confirmed that the instance is serving complete pages, add it back to the load balancer pool to resume serving production traffic.
- Purge the affected page(s) from the CDN cache to remove any truncated or incomplete responses cached at the edge.
- Monitor the site to confirm that complete responses are now being served.