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Overview of microblog features, feeds, and the Distributed Cache service in SharePoint Server 2013

SharePoint 2013
 

Applies to: SharePoint Server 2013

Topic Last Modified: 2014-01-13

Summary: Learn about microblog features, newsfeed, and the Distributed Cache service in SharePoint Server 2013.

Microblogs allow users to quickly broadcast information to a central location while enabling other users to create a public dialog by responding with comments. Important information and news can be shared quickly among peers while keeping conversations in context.

NoteNote:
Before reading this article, you should understand the definitions and concepts in Social computing terminology and concepts in SharePoint Server 2013.

Microblog features are included in SharePoint Server 2013. On a microblog, users can post a message that they want to publicize and create a public dialog about. Users can include text, URLs, pictures, and videos. HTML tags are not accepted. The maximum length of a post is 512 characters. After a message is posted, it is immediately seen in the newsfeed. Other users can see this post and reply to the original message. The maximum number of replies that can be associated with a post is 100 replies.

Users can include tags in the body of the message to highlight interest in the thread to others following that tag. Users can also mention (@Mention) a particular user to get the attention of that user from the post or reply they are submitting. For example, if a particular user is a subject matter expert in a particular area, users might @Mention the user to get that user's attention and maybe a response to the current conversation. Users can like a post or reply in the newsfeed as a way of giving public validation that a post or reply was useful to them. By liking an item, a user can easily reference that item from the Likes newsfeed. Users can also follow people, sites, tags, or documents that they are interested in. When following an entity, updates and new information about that entity will be displayed in the user's newsfeed.

In this article:

The following diagram shows the architecture of the microblog features, feeds, and the Distributed Cache.

NoteNote:
To access any microblog feature or the feeds, the user must have a user profile and a My Site in SharePoint Server 2013. Anonymous posting is not supported in any microblog feature in SharePoint Server 2013.

Figure: Architecture of microblog features, feeds, and the Distributed Cache

Architecture of microblog and dependencies

Activities are posts and replies that can be either user-generated or system-generated. There are several types of activities in SharePoint Server 2013. These include the following:

  • 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.

In SharePoint Server 2013, the newsfeed (or just simply the feed) displays activity information to users. Users access the feeds from a user's My Site. In SharePoint Server 2013, a user's My Site has several feeds available from which to choose. These different feeds show different views of activity information by filtering or pivoting on activity metadata. The different feeds available to users from their My Sites include the following:

  • Newsfeed   This is the default view when visiting a user's My Site. The Newsfeed contains recent activities from followed entities. The Newsfeed displays 20 items and is sorted in reverse chronological order. Items listed in the Newsfeed are activities from entities a user follows, and conversations from any site feeds the user follows. Site feeds are explained later in this article.

  • Everyone   The Everyone feed shows the last 20 posts or replies across all users. The distinction between the Everyone feed and the Newsfeed is that the Newsfeed only shows activities from entities the user is following.

  • Activities   The Activities feed shows all activities associated with a user, including system-generated activities. The Activities feed represents the most accurate view of a user's activities because it shows all activities and not just recent activities, which occurs with the Newsfeed. This feed is also seen when users browse to their profile or About Me page for a user.

  • Mentions   The Mentions feed for a user displays all posts or replies where that user was mentioned.

  • Likes   The Likes feed displays a list of posts or replies that the user has liked. This is not related to the I Like It feature from SharePoint Server 2010.

NoteNote:
When a user stops following an entity, the entity is removed from the user's followed entities list. The user will no longer see activities from that entity in their Newsfeed.

Site feeds   Activities are publicly accessible unless the activity refers to content that the user does not have access to. If feed functionality is required for a restricted group of users, a site feed should be used. Site feeds display posts and replies among the users of the group. Site feed posts and replies display in the Newsfeed of a user only if the user has access to the site feed. Site feeds do not display system-generated activities. By default, the site feed feature on a team site is enabled. When you assign permissions to a team site that hosts a site feed, consider the following:

  • Access to the site feed is restricted to the users specified in the permissions list.

  • Users can post or reply only if they have the appropriate permissions.

  • Security trimming is enforced. This means that no site feed activities will appear in the search results of a user who doesn't have access to the team site.

  • Site feed activities appear in a user's Newsfeed if the user has access to the team site.

As shown in the earlier figure, when an activity is generated in SharePoint Server 2013, the following occurs (the numbers in the list correspond to numbers in the figure):

  1. Some activities are saved to the content databases. If the activity is a user activity or site activity, the activity is saved to the My Sites content database. If the activity is a site feed activity, the activity is saved in the team sites content database. Tag activities and document activities are not saved to content databases.

  2. Activities are written to the Distributed Cache. The Distributed Cache is described later in this article.

  3. Updates appear in the feed. Users receive visual indicators to notify them of new updates. When a user refreshes the browser, updates are shown to the user.

NoteNote:
There are no dedicated databases that directly support the microblog features and feeds. Microblog features and feeds use the My Sites and team sites content databases only. Activities written to the My Sites content databases are never deleted. This should be planned for when you plan a My Sites deployment.

Distributed Cache service   The Distributed Cache service provides caching features in SharePoint Server 2013. The microblog features and feeds rely on the Distributed Cache to store data for very fast retrieval across all entities. The Distributed Cache service is built on Windows Server AppFabric, which implements the AppFabric Caching service. Windows Server AppFabric installs with the prerequisites for SharePoint Server 2013.

Any server in the farm running the Distributed Cache service is known as a cache host. A cache cluster is the group of all cache hosts in a SharePoint Server 2013 farm. A cache host joins a cache cluster when a new application server running the Distributed Cache service is added to the farm. When using a cache cluster, the Distributed Cache spans all application servers and creates one cache in the server farm. The total cache size is the sum of the memory allocated to the Distributed Cache service on each of the cache hosts.

The Distributed Cache service can run in dedicated or collocated mode. When running in dedicated mode, the Distributed Cache service is started and all other services are stopped on the server. In collocated mode, the Distributed Cache service is running along with other services on the server.

NoteNote:
We recommend that in collocated mode, all non-essential services be shut down to reduce the competition for memory resources.

In SharePoint Server 2013, there are several caches that exist, all of which depend on the Distributed Cache service. The following table lists these caches.

Table: Different caches that depend on the Distributed Cache service

Name Cache name Description

Login Token Cache

DistributedLogonTokenCache

This cache stores the security token issued by a Secure Token Service for use by any web server in the server farm. Any web server that receives a request for resources can access the security token from the cache, authenticate the user, and provide access to the resources requested.

Feed Cache

DistributedActivityFeedCache

This cache stores activities and conversations for use by the feeds on a user's My Site.

Last Modified Time Cache

DistributedActivityFeedLMTCache

This cache stores time stamp information for all Feed Cache entities

OneNote Throttling

DistributedBouncerCache

Access Cache

DistributedAccessCache

Search Query Web Part

DistributedSearchCache

Security Trimming Cache

DistributedSecurityTrimmingCache

App Token Cache

DistributedServerToAppServerAccessTokenCache

View State Cache

DistributedViewStateCache

Default Cache

DistributedDefaultCache

This cache can be used by any feature.

The microblog features and feeds rely on the following two caches: the Last Modified Time Cache and the Feed Cache.

  • Feed Cache   The Feed Cache stores recent activities and recent conversations for all entities

  • Last Modified Time Cache   The Last Modified Time Cache is used to determine the last modified time for all items in the Feed Cache.

As shown in the earlier figure, when constructing feeds, such as the Newsfeed or the Everyone feed, the following occurs (the letters in the list correspond to the letters in the figure):

A. The feed queries the Last Modified Time Cache to retrieve time stamp information and metadata of recent activities.

B. This information is then used as input to query the Feed Cache to retrieve activity data.

C. The requested feed is then constructed by using the activity data retrieved from the Feed Cache.

For each entity, the Feed Cache assigns a portion of memory known as a cache bucket to store recent activity data for that entity. Entities include users, tags, sites, and documents. Cache buckets only store recent activities. Many cache buckets will be empty because not all entities will have recent activities. By default, recent activities are kept for seven days.

ImportantImportant:
The Last Modified Time Cache only lives on one cache host in the cache cluster. Also, the Feed Cache stores recent information about all entities. It is important that proper capacity planning be conducted for the cache hosts. For more information, see Plan for feeds and the Distributed Cache service in SharePoint Server 2013.

System events, such as a power failure or unexpected restart of a server, affect the Distributed Cache service. Also, a planned activity, such as an administrator shutting down an application server that is running the Distributed Cache service to perform operational tasks, affects the Distributed Cache service. These actions reset and empty the Feed Cache and the Last Modified Time Cache. In this situation, repopulation of recent activities is required. Repopulation involves reloading saved data from the content databases into the Last Modified Time Cache. After the Last Modified Time Cache is reloaded, the next user to visit their My Site starts the repopulation of data in the Feed Cache. For more information, see Manage Feed Cache and Last Modified Time Cache repopulation in SharePoint Server 2013.

Some benefits of using microblog features, feeds, and the Distributed Cache include the following:

  • Allows users to stay in touch with individuals and specific groups of people over time and distance.

  • Allows users to stay informed about what's going in the organization.

  • The focus of the interactions is around people or teams, and not so much the topic being discussed.

  • It is difficult to keep track of activities related to documents, discussions, and lists in SharePoint without manually visiting the item regularly. Feeds collect and deliver information to users that they would otherwise have to spend time searching for.

  • The feed gives users a single place where they can stay up-to-date with all of the content and people they work with.

  • Allows quick conversations to take place.

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