Dynamic cohorts

Dynamic cohorts plugin allows dynamically add and remove users from cohorts based on configured rules, which themselves are composed of conditions.

Versions and branches

Moodle Version	Branch
Moodle 4.1 - 4.3	MOODLE_401_STABLE
Moodle 4.4+	MOODLE_404_STABLE

Installing via uploaded ZIP file

1. Log in to your Moodle site as an admin and go to Site administration > Plugins > Install plugins.
2. Upload the ZIP file with the plugin code. You should only be prompted to add extra details if your plugin type is not automatically detected.
3. Check the plugin validation report and finish the installation.

Installing manually

The plugin can be also installed by putting the contents of this directory to

{your/moodle/dirroot}/admin/tool/dynamic_cohorts

Afterwards, log in to your Moodle site as an admin and go to Site administration > Notifications to complete the installation.

Alternatively, you can run

$ php admin/cli/upgrade.php

to complete the installation from the command line.

Similar plugins

There are similar plugins that can add users to cohorts dynamically based on user profile fields.

• Profile field based cohort membership https://moodle.org/plugins/local_profilecohort
• Smart Cohort https://moodle.org/plugins/local_cnw_smartcohort
• Auto-cohort plugin https://moodle.org/plugins/local_cohortauto

However, "Dynamic cohorts" plugin gets this all to the next level as it provides an API for other plugins to implement pretty much any condition that can limit users from mdl_user table by SQL.

How does it work?

There are two concepts, rules and conditions.

Conditions

Conditions are simple predicates which assert something about a user in the system. Any plugin may specify a condition. As an example conditions related to user profile fields. These can be used to match users based on the value of a profile field.

Built-in conditions

• Authentication method (Manual, SAML and etc)
• Cohort fields (if a user is a member of cohort(s) matching specific cohort fields like cohort name, context, custom fields and etc)
• Cohort membership (if a user is a member of cohort(s)).
• Course completed (if a user has completed a course).
• Course not completed (if a user has not completed a course).
• User created time (time since a user was created).
• User custom profile fields (text, menu, date and autocomplete types are supported).
• User enrolment (if a user is enrolled into a course).
• User last login (time since a user last logged in).
• User role (if a user has a role in a given context)
• User standard profile fields (e.g. first name, last name, username, auth method and etc).

Rules

Rules are what determine if a user will be added or removed from a cohort. A rule is defined by few things:

1. A cohort
2. A set of conditions
3. A logical operator to be applied for conditions (OR/AND)

For users to be added to the cohort specified by a rule, they must match all of rule's conditions (logical operator AND) or any of rule's conditions (logical operator OR).

NB: A cohort can be managed by one and only one rule. This is to prevent rules competing over users in a cohort (e.g., to avoid situations where Rule A wants users a, b, c to be in a cohort, but Rule B wants to remove user c from the same cohort).

Rules can be processed by two mechanisms:

1. By cron: When a rule is created or updated, there may be many users that need to be added or removed from a cohort. This process is handled by cron, and depending on how many users are matched by a rule, this process can take some time. For rules matching large sets of users, some configuration options are provided which may be useful to server administrators.
2. By event: rules may also listen to certain events. When one of these events triggers, appropriate rules will be checked and the user will be added to the appropriate cohort immediately. For example, the User standard profile field rule listens to the "User created" and "User updated" events.

Configuration

Prerequisites

1. At least one manually created cohort (See Site administration > Users > Cohorts)

Creating a rule

1. Navigate to Site administration > Users > Accounts > Dynamic cohorts > Manage rules
2. Press the "Add a new rule" button
3. From this form you can specify the cohort users will be added to, and add any conditions available in your system. As metioned above, a user must match all conditions to be added to the cohort
4. Press the "Save changes" button

You will be directed to the manage rules page where you can review your rule before enabling it by clicking the eye.

Note: It is important to review your new rule to make sure it is configured properly. Consider carefully how many users are affected by the rule (displayed in the table) before enabling it. For rules operating on large sets of users see rule processing options

Any subsequent edits to a rule will disable it and require you to review and re-enable it.

Rule processing options

Rules are processed regularly by cron; by default cron will add each user to the specified cohort one by one. For large sets of users, this can take a long time and potentially block other cron tasks.

To mitigate this, an option is provided to process "in bulk" instead of adding them to a cohort one at a time. To enable it for a rule:

1. Go to the rule edit table
2. Check the "Bulk processing" checkbox
3. Save the rule and review it before enabling

Technical details

Condition implementation

Quick start

Any plugin can easily implement a condition by adding classes in the \local\tool_dynamic_cohorts\condition namespace. Each condition must extend the base_condition class. As an example, the itself provides some conditions; the directory structure is as follows:

tool_dynamic_cohorts
└── classes
    └── local
       └── tool_dynamic_cohorts
           └── condition
               ├── auth_method.php
               ├── cohort_membership.php
               ├── user_custom_profile.php
               └── user_profile.php

See cohort_membership.php for an example implementation of a single rule. Any plugin wishing to add a rule must simply add similar class inside its own directory. tool_dynamic_cohorts will automatically discover new rules.

Triggering on event

Any condition can specify a list of events to listen to by overriding the get_events method. Simply return a list of events. See user_custom_profile.php for an example.

Task processing

Task processing is orchestrated by a simple mechanism:

1. A scheduled task runs periodically which gets all enabled rules, then queues an ad-hoc task to process the rule (i.e., one ad-hoc task per rule)
2. The ad-hoc task will either: a) Iterate over all users, adding them to the cohort one at a time (via the cohort API) b) If bulk processing is enabled, users will be inserted directly in to the DB in batches, bypassing the core API

Warm thanks

Plugin funded by Murdoch University, Perth, Western Australia (https://www.murdoch.edu.au/)

License

2024 Catalyst IT

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see https://www.gnu.org/licenses/.