The question: What happens to the experience if xConnect is down?
Content Delivery Role
The Content Delivery Role uses the SessionEnd of the HTTP Request lifecycle to push session data to the xConnect Collection Service. When the xConnect Collection Service is down, Sitecore CD will wait until services are restored and then push data from the sessions.
If using InProc session management, and the CD server recycles it's app pool before it's able to push the session to the Collection Service, that session information is lost.
Recommended practice is to use a Session database like SQL or Redis.
Tracker and Identification
If the xConnect Collection Service is down, Tracker and xConnect Submit batches will fail. This will mean personalization will not fire, but the Site will still work.
Assuming there's a Session Cookie, session data will still collect.
Content Management Role
Analytics and Marketing Operations
If the xConnect Reference Data service is down:
- Most Analytics reporting will not show.
- Experience Profile will not show users.
- List Segments will not display
- Marketing Automation will not work.
If xConnect Collection Search Indexer is down, the processing pools will not hydrate and the processing server will not do anything.
If the xConnect Reference Data service is down, Processing will error out with xConnect Issues. The processing pool should remain until the problem is resolved.
The Reporting Role of Sitecore does not have a dependence on xConnect. Merely the Reporting Database in SQL.
If this service is down, no collection of data from the CD (or CM if running the xDB migration tool) will occur.
Collection Search Index Worker
If this service is down, the xdb index will not update.
If this service is down, Marketing Automation Engine and Sitecore Analytics will not work.
Marketing Automation Engine
If this service is down, Marketing Automation plans will not advance.
Marketing Automation Reporting
If this service is down, reporting in Marketing Automation will not work.
If this service is down, ML Cortex processing will not work.