Below a story about non-working decaching after upgrading to SDL Web 8.5 CMS.
The project I work on has this environment configuration:
- SDL Web 8 CMS (with update SP1 and Cache Channel Service)
- DD4T 2.1 based .NET web application
- ApacheMQ as JMS solution
- We use DD4T.Caching.ApacheMQ NuGet package
- Hosted in Azure cloud
Given this setup, everything is configured to flush the Application cache when a Content Manager publishes a Page, Dynamic Component Presentation or Taxonomy from the CMS. This works really well and we achieve the two most important goals: High-performance websites + No outdated content.
Upgrade to Web 8.5 problem
But then we decided to upgrade to SDL Web 8.5 (with a new server). The upgrade process itself is not as painful as it was in the past, but we had an issue: de-caching mechanism did not work anymore. We did the most obvious checks:
- Check config settings of microservices
- Firewall settings (ports open?)
- MQ dashboard (publishers, subscribers, and messages)
- Check log files for exceptions
- Review the Topology Management config (java -jar .\discovery-registration.jar read)
Mysteriously, everything was fine. After some WebApp debugging sessions I found the issue. The JMS messages were changed and the TCM URI is now prefixed with '1:'. Maybe SDL decided to include the CacheEventTypeId? Examples:
- SDL Web 8 sends 17:3565 for pages.
- SDL Web 8.5 sends 1:17:3565 for pages.
- SDL Web 8 sends 17:52916:154 for DCPs.
- SDL Web 8.5 sends 1:17:52916:154 for DCPs
RCA and solving the issue
This causes a lookup issue when looking for depending cache items to flush within the TridionBackedCacheAgent. The agent stores pages in cache with 17:3565 and CCS tries to flush the cache with 1:17:3565. Since we have a custom implementation of the CacheAgent (for either reasons) we could fix it easily by using this code fragment in the CacheAgent:
private Regex RemoveFirstElemWhenWeb85 = new Regex("^(1:)(.*)");
private string GetDependencyCacheKey(string tcmUri)
return "Dependencies:" + this.RemoveFirstElemWhenWeb85.Replace(tcmUri, "$2");
This code backward compatible with older version of Web/Tridion as long as you do not have a publication with the ID of 1 :-)