Recently I heard about situation when there were issues with installing K2 for SharePoint application related with missing Distributed Cache Service on SP server (there were related errors in SP logs and errors when adding K2 app in SP). This forced me to learn a bit about this Distributed Cache Service technology.
As with many of utility services or infrastructure things which supposed to do their job silently and transparently you may appreciate their usefulness and complexity only when things went wrong with them. Once such stuff broken you first realize how useful it was and what doesn’t work without it, and next when you trying to fix the stuff you start learning about complexities of this stuff 🙂
Short definition: SP Distributed Cache is a service that provides caching functionality which runs on an application server in SharePoint Server 2013. All microblog features in SharePoint Server 2013 depend on the Distributed Cache service.
The way Distributed Cache being leveraged by SP and solutions based on SP definitely deserves separate post along with clarifying the question when it is really required and what doesn’t work without it.
So far I just note that this service should be in place and properly configured for SP 2013 farms with multiple web front ends (on all WFEs).
Most useful links which I found researching this are (exactly in this order):
First 2 posts by Josh Gavant [MSFT] are definitely must read if you want to understand how caching works in SP.
UPDATE: I also posted a question on serverfault.com back in December 2014 to get some comment on which SP features necessitate/require Distributed Cache Service, and only recently some answer come up. Main take away from this answer is that “Overview of microblog features, feeds, and the Distributed Cache service in SharePoint Server 2013” article on TechNet contains “Different caches that depend on the Distributed Cache service” table which lists what types of cache in SP depend on Distributed Cache Service.
Also: The Distributed Cache service provides in-memory caching services and does not have a dependency on databases for several features in SharePoint Server 2013. Some of the features that use the Distributed Cache service include:
- OneNote client access
- Security Trimming
- Page load performance
When the service is enabled, these features use the Distributed Cache for quick data retrieval. Blob Cache and Output Cache do not use a distributed caching service since these types of cache exist on each Web Front End server in the farm.
The microblog features and feeds rely on the Distributed Cache to store data for very fast retrieval across all entities.Following activities depend upon on news feed.
- Microblog activities This includes posts, replies, likes, mentions, or tagging an item.
- Following activities This includes when a user follows people, documents, sites, or tags.
- User profile activities This includes birthday, job title change, anniversary, updates made to Ask Me About, creating a new blog post, or posting on a Community Site.
- Document activities This includes when a document is edited or a document is shared.
\nThanks to Waqas Sarwar MCSE for his answer.