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Question

AEM - Issues with Cache Flush in AEM As Cloud | AEM As Cloud - Content Not Refreshing After Publish

Forum|Forum|1 year ago
May 2, 2024
3 replies
2349 views

Hi All,

We're facing a challenging issue with our AEM as a Cloud project. Our caching had been working correctly for a long time, but recently we've noticed that content isn't refreshing after publishing or even after the max-age is reached. Below are our findings from the debugging we've done so far.

Additionally, our dispatcher cache settings haven't been changed in a very long time.

As per the documentation https://experienceleague.adobe.com/en/docs/experience-manager-cloud-service/content/implementing/content-delivery/caching#cache-activation-deactivation , our vhost configurations appear to be correct.

2. The CDN cache shows a MISS upon reaching max-age, but the content retrieved from the server remains outdated. This suggests potential caching within the Fastly CDN or a persistent Dispatcher cache.

3. Adding the Surrogate-Control header (as documented by Fastly https://www.fastly.com/documentation/reference/http/http-headers/Surrogate-Control/ ) to bypass the Fastly cache yielded mixed results. While the initial requests retrieved the updated content, subsequent attempts did not.

4. We removed all caching headers from the Dispatcher files. As per the AEM documentation [https://experienceleague.adobe.com/en/docs/experience-manager-cloud-service/content/implementing/content-delivery/caching#:~:text=New%20default%20caching%20behavior,traffic%20is%20set%20to%20private. ], this should trigger the default private cache behavior (with a max-age of 600 seconds). However, the browser cache still reflected a max-age of 300 seconds, and content updates weren't reflected after 300 seconds.

5. Bypassing the Dispatcher cache entirely via URL confirmed that the content is indeed published and available on the Publish server.

We're at a loss for the cause of this issue. Any guidance on further debugging or resolving this problem would be greatly appreciated.

P.S. Due to the client's strict access policies, I am unable to access Cloud Manager for further investigation.

Thanks in Advance

Veena ✌

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aanchal-sikka

Community Advisor

@veenavikraman

If possible enable debug logs on dispatcher. That would really help !

Please assure s-max-age is not used in Cache-Control. Use only Surrogate-control.
Please check if the Dispatcher Flush is configured the pipeline after deployment: https://experienceleague.adobe.com/en/docs/experience-manager-cloud-manager/content/using/pipelines/production-pipelines
- If not configured, the headers from old cache might still be effective.
If possible implement SCD to flush Dispatcher on Demand
If you use Adobe provided Fastly CDN, then you can flush CDN on demand http://experience-aem.blogspot.com/2023/01/aem-cloud-service-invalidate-dispatcher-purge-fastly-cdn-cache-api.html

For detailed analysis via headers I had authored a blog some time ago: https://techrevel.blog/2023/09/05/exploring-aem-request-and-response-headers-analysis-of-browser-cdn-and-dispatcher/

Aanchal Sikka

VeenaVikraman

Author

Community Advisor

Thanks @aanchal-sikka . We do not have access to Cloud Manager. But I will pass this info to the team who can check that. We do have s-max-age as we have another CDN infront of Fastly. Why do you think we should not use s-max ?

Also regarding

If possible enable debug logs on dispatcher. That would really help !
- Please assure s-max-age is not used in Cache-Control. Use only Surrogate-control.
- Please check if the Dispatcher Flush is configured the pipeline after deployment: https://experienceleague.adobe.com/en/docs/experience-manager-cloud-manager/content/using/pipelines/production-pipelines
  - If not configured, the headers from old cache might still be effective.
- If possible implement SCD to flush Dispatcher on Demand
- If you use Adobe provided Fastly CDN, then you can flush CDN on demand http://experience-aem.blogspot.com/2023/01/aem-cloud-service-invalidate-dispatcher-purge-fastly-cdn-cache-api.html
For detailed analysis via headers I had authored a blog some time ago: https://techrevel.blog/2023/09/05/exploring-aem-request-and-response-headers-analysis-of-browser-cdn-and-dispatcher/
The content is properly flush when deployment happens. But we see issue in the flush only when the content activation is happening

aanchal-sikka

Community Advisor

@veenavikraman

As per the documentation, "Use the Surrogate-Control header to control CDN caching independent from browser caching.

Since, you have custom & Fastly CDN, you might need both:

s-max-age (as per the custom CDN)
surrogate-control (Fastly will ignore s-max-age, when surrogate-control is present).

Both, CDN need to be flushed to assure that latest content is fetched from dispatcher.

Adobe can flush entire CDN on request. They can also share a curl command for resource-based flush.

Aanchal Sikka

M

Meenapl

@veenavikraman In addition to enable Dispatcher log, good to see if the cache folder in dispatcher is configured with necessary permissions even then flush can't happen appropriately.

MukeshYadav_

Community Advisor

Hi,

Just to confirm that it is dispatcher level caching issue only, we can check if it serve the right content when we append any query param. As in general URL with query param is not cached served from cache.

Thanks

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