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Status: 50%

OVERVIEW

This document describes the main design and implementation decisions behind the "Group Mentions” feature. This feature provides ways for a MM user to mention groups and notify their members (and invite the ones that are not in the channel to the channel).

GOALS

  • describe the changes and additions to the backend architecture (API and Storage)

  • describe the UX changes (webapp and redux)

  • describe the mobile changes.

SCOPE

In:

  • ability to mention group(s) in a channel

  • ability to notify the members of the group(s) that are being mentioned

  • ability to enable/disable the referencing (mention) of a group in the System Console

  • display a warning if the group mention will trigger notifications to more than X number of users

  • ability to enable or disable notifications per group

Out:

TBD

BACKGROUND READING

  1. Feature specification

  2. High fidelity designs

TERMINOLOGY

“Group-constrained” - when a group is linked to a channel or team and syncing its group members is turned on.

SPECIFICATIONS

High-level Architecture

Group Mentions

We can split the group mentioning flow into two phases: Build Suggestions and Notify Members. We will detail the design and the API, storage and client supporting changes for both of them.

Phase 1: Build Suggestions

Design

The flow of actions for this phase will be:

  1. we fetch the group(s) objects from the server and use them to populate the client state

  2. we filter the client state if the current channel or team is group-constrained or not and select the groups that fulfill the right conditions (see below)

  3. we populate the mentions suggestion list with the names of the groups obtained in the previous step.

Group-Constrained Channel/Team Status

A channel or a team can be in two states:

  1. constrained to the group(s)

  2. not constrained by any group.

Depending if the current channel and/or the containing team is group constrained , we can have the following group mentioning cases:

  1. If the current channel is constrained by the group(s), the user in the channel can only mention one of these groups.

  2. Otherwise, if the current team is constrained to one or more groups, the user can only mention one or more of these groups.

  3. If neither the current channel is constrained, nor the current team, then the user can mention any group constrained to any channel/group in the system. (currently all groups in MM are linked groups).

While we do not have a good grasp of many groups we can have in an org, we made the assumption that the number is small enough where we could fetch them from the server more than once during a session (we optimize this action by retrieving only the mentionable ones). The group mention flow is initiated from a channel's textbox; it is an expensive operation to repeatedly fetch the group(s) from the server as the user types - we will fetch the groups and populate the client state (depending if the channel/team is group-constrained or not) once per team initialization (which means that if we switch teams in the work session we will fetch the teams from the server again).

Future Work: Ideally, the groups will need to be fetched only once, at server start, not at every team change (and then only updated based on group-related System Console actions).

Duplicate group names

When we enable group mentioning on a group in the System Console, we are also generating the actual group name property from the group’s display name (e.g. from “software developers” to “@software-developers”). This happens at the server-side and since we enforce the uniqueness of the name column in the UserGroups table, there is a potential of erroring by throwing a SQL exception if there is already a group with the same name already stored. 

Future Work: Fully address the duplicate group name case. One solution would be to surface the duplicate error in the UI and allow the user to specify a different (custom) group name if the current one is a duplicate of another.

Groups with no team members

When we build the list of groups to mention, the groups are added to the list if the channel/team are group-constrained or not. However, it could be that for some of these groups none of their members are members of the current team. Since the members of these groups are not going to be notified, one solution is to avoid selecting them for inclusion in the mentions suggestion list to begin with. The current plan is to include these groups in the suggestion list.

Future Work: Filter out the groups that have no members in the current team from inclusion in the mentions suggestion list.  Another proposed solution is to add an invite flow:  “invite them now” quick link.

UI/X (Webapp)

Group Mention Settings Toggle Panel

  • we will add a new “Group Mention Settings” toggle widget containing a toggle in the Group Configuration details panel in the System Console. We will change the group states on the server at every UI toggle action (there is no Save action).

Future Work: converting this toggle into a proper “validate and update on Save" panel - the server state gets updated only when we click Save in the Group Configuration panel

Channel Textbox Suggestions List

  • when displaying the group mention in the suggestion list, we plan to include the group name and the group display name. There has been discussion to also display the member count (e.g. : “@software-developers - software developers - 4 members”)

Future work:  Add a member count to the @group-name like : “@software-developers - 4 members”

UI/X (Redux)

Selectors:

  • searchAssociatedGroupsForReferenceLocal - allows for searching of mentionable groups based on the user entered text

  • getAssociatedGroupsForReference - returns the list of groups that constrain a channel and/or team (or not). If the current user’s role does not have USE_GROUP_MENTIONS permission, it will return an empty list.

  • getGroupsAssociatedToTeamForReference

  • getGroupsAssociatedToChannelForReference

  • getAllAssociatedGroupsForReference

Actions:

  • getGroups

  • patchGroup 

  • getAllGroupsAssociatedToChannelsInTeam

REST API

  • we will add the following new endpoints:

Team : …/ groups_by_channels  getGroupsAssociatedToChannelsByTeam(GET) - returns for a team, a map of channels constrained by groups and the corresponding groups.

  • we will update the following GetGroups* API endpoints with the additional filter_allow_reference filter (default is false), to be able to retrieve only the groups that are enabled for mentions.

GetGroupsByChannel

GetGroupsByTeam

GetGroupsAssociatedToChannelsByTeam

GetGroups

Storage

  • we will add a new SQL stored-procedure:  getGroupsAssociatedToChannelsByTeam

Tickets

Display group mentions in suggestions list in the main channel textbox

https://mattermost.atlassian.net/browse/MM-23016

Enable or Disable group mentions

https://mattermost.atlassian.net/browse/MM-23015

WebApp - Highlight Group Names in chat window

https://mattermost.atlassian.net/browse/MM-23159

Phase 2: Notify Members

After the groups have been selected from the suggestion list in the channel textbox, we need to notify their members about the mention.

Design

The flow of notifying group members will use the existing SendNotifications function and insert checks for groups where needed.

  • The first step added will be to check if the user creating the post and has access to PERMISSION_USE_GROUP_MENTIONS, if not then the behaviour of SendNotifications will be unchanged

  • If group mentions are enabled then all groups that have AllowReference = 1 will be added to memory

  • The ExplicitMentions struct will have a new attribute GroupMentions to store the groups mentioned by the Post.Message.

  • Once all groups are added to the GroupMentions map, group members that exist in the channel will be added to the Mentions map as confirmed mentions in the channel.

  • Group members that exist in the team but not in the channel will be added to OtherPotentialMentions and will have an invite message generated for them using the existing logic.

  • If there are no group members in the team that the message is sent to a system message will return letting the user know that the group mentioned has no members in the current team.

Warning Modal

  • in the notification phase, when the aggregated number of group members to mention is above a certain threshold, we are showing a warning modal  (see wireframe), the text message in the modal includes the user count from the largest group in the collection. This is a compromise solution, due to performance constraints - fetching the accurate count, including membership overlaps, from the server would introduce a delay in sending the notification.

  • If more than 5 members of a group exist in the channel that the group being mentioned, the user will get a warning modal mentioning that they will be notifying the group with the most number of members within that channel. For example, if we mention @developers @board and @developer has 10 users within the channel while @board only has 2 members in the channel, the warning modal will explain that you are about to notify @developers and @board with 10 members in the channel. We were unable to display the accurate number of users being notified due to the bottleneck of trying to avoid duplicates since a user can be found in multiple groups. If a group has a repeating user and requiring to find the UNION of all the group members within the channel would cause significant performance degrade which is why we opted to go with the alternate solution of displaying the maximum number of users being notified within a group.

Future work: Investigate a better solution?

UI/X(Webapp)

  • The markdown component will be modified to use getAllUserMentionKeys which contains the union of `getCurrentUserMentionKeys and getCurrentUserGroupMentionKeys. This will ensure that group names will be highlighted for the user as expected.

  • The web app filters all the mentions and compares it to the allow_reference groups available through redux to see which ones are being mentioned. In the redux state, when you visit a channel, all the groups that have members within that channel are available in state.entities.channelMemberCountsByGroup[channelID]. All the groups being mentioned will be retrieved from the state and then the one with the most channel members will be grabbed and used to display the number of users being notified. However, if groups are being mentioned alongside @all or @channel, then the total number of channel members - 1 will be used instead.

UI/X(Redux)

  • A new selector will be added to get the list of groups that the current user can be mentioned by: getCurrentUserGroupMentionKeys this will be used to determine which @group mentions should be highlighted in the chat facing UI. This selector will be used inside of getAllUserMentionKeys to return the result merged with getCurrentUserMentionKeys (which contains regular mentions such as first name / user name etc).

  • In the redux side of things, a new function getChannelMemberCountsByGroup has been added which takes a channelID and a boolean includeTimezones and returns a list of groups with members within the channel and number of members in that channel. If includeTimezones is true then we also get the different number of timezones amongst the users in that group. This information is used by the web app to determine which group has the most number of users in the channel to for displaying the number of users being notified after the message has been sent.

REST API

we will add the following new endpoints:

channel: “.../ member_counts_by_group/" channelMemberCountsByGroup` (GET)

  • since we extend the range of calls to the GetGroups* methods from the SystemConsole to the chat-facing area will remove the permission check from the following API calls:

GetGroups

GetGroupsForTeam

…

Storage:

  • we will add the following new stored procedures:

GetMemberCountsByGroup  - returns a slice of ChannelMemberCountByGroup for a given channel which contains the number of channel members for each group and optionally the number of unique timezones present for each group in the channel

GetMemberUsersInTeam - returns a slice of users that are members of a group and exist in a team. The intersection of (users in team) & (users in group)

GetMemberUsersNotInChannel - returns a slice of users that are members of a group that exist in the team that the channel belongs to but do not exist in the channel. The intersection of (users in team) & (users in group) & (users not in channel)

Tickets

Group Mentions - Show a confirmation dialog when mentioning a group with too many users

https://mattermost.atlassian.net/browse/MM-23264

Send notifications to the @-mentioned group members

https://mattermost.atlassian.net/browse/MM-23017

Supporting Work

Storage

  • we will add a new column to the UserGroups table:

    AllowReference : boolean

Permissions

  • we will add a new permission USE_GROUP_MENTIONS 

Tickets

Create use_group_mentions permission

https://mattermost.atlassian.net/browse/MM-23019

Websockets updates

Ticket: Ensure websockets are updating the referenceable groups (et al) in Redux for group-mentions

https://mattermost.atlassian.net/browse/MM-23395

CLI

Out of scope.

Configuration

None.

Plugins

Out of scope.

CREDITS

Thanks to Martin, Hossein, Farhan and Scott for great suggestions and brainstorming.

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