A dockerised service that replaces the default nbgrader Exchange.

• What is nbexchange
• Why nbexchange
  • Compatibility
• Documentation
  • Database relationships
• Installing
  • nbexchange service
    • Helm
  • nbgrader jlab plugin
• Configuration
  • Configuring the nbexchange service
    • user_plugin_class revisited
• Contributing
  • Releasing new versions

What is nbexchange

nbexchange is an extension to nbgrader which provides a mechanism for assignments to transferred in a distributed Jupyter Notebooks environment.

The default for nbgrader is to assume all users are on the same computer, and files are copied from one directory to another - thus:

When using jupyter notebooks in a distributed [dockerised] system, there is no common filesystem - so an alternative mechanism is needed - something that allows files to be transfered via some independant service - eg:

nbexchange provides that intermediate filestore that is covered by this project. The plugins for nbgrader to use this exchange service are provided by a separate project: nbexchange_jlab_plugin

Why nbexchange

From nbgrader: Assignments are created, generated, released, fetched, submitted, collected, graded. Then feedback can be generated, released, and fetched.

The exchange is responsible for recieving release/fetch path, and submit/collect cycle. It also allows feedback to be transferred from instructor to student.

In doing this, the exchange is the authoritative place to get a list of what's what.

nbexchange is an external exchange plugin, designed to be run as a docker instance (probably inside a K8 cluster)

It's provides an external store for released & submitted assignments, and the feeback cycle.

Following the lead of other Jupyter services, it is a tornado application.

The team that created the inital code use nbexchange in a cloud environment, with multiple organisations using a central exchange service. Courses [and this assignments] are differentiated using an org_id - if you do not need this feature, just set it to 1 for everthing.

Compatibility

This version installs nbgrader 0.9.5 (which makes it compatible with JupyterLab & Notebook 7)

Documentation

This exchange has some assumptions because of the environment required it.

There are the following assumptions:

• You have an API for authenticating users who connect to the exchange (possibly Jupyterhub, but not always)
• Usernames will be unique across the whole system
• Internal storage is in two parts:
  • An sql database for metadata, and
  • A filesystem for, well, files.
• There will always be a course_code
  • There may be multiple assignments under one course,
  • assignment_codes will be unique to a course
    • assignment_codes may be repeated in different course_codes
    • Note that default nbgrader does not distinguish assignment_codes across different course_codes, within the same gradebook database.
• There will always be an organisation_id
  • course_codes must be uniqie within an organisation_id,
  • course_codes may be repeated in different organisation_id

Database relationships

Installing

nbexchange is a two-part system: it requires

1. This service, the nbexchange service, to be running (we run it in a docker container.)
2. The plugins to be installed in the jupyter notebook (which will also install nbgrader): nbexchange_jlab_plugin

nbexchange service

The nbexchange is designed to be run as a docker instance, possibly in a kubernetes cluster

See the Dockerfile / docker-compose.yml files for creating the service.

Helm

The service can be deployed via helm, ie

helm install --name nbexchange --namespace default ./chart -f myconfiguration.yaml

nbgrader jlab plugin

Installing nbexchange in a jupyter notebook will automatically install nbgrader.

nbexchange is not released to Pypy or anaconda, however you can install direct from GitHub - eg:

pip install https://github.com/edina/nbexchange_jlab_plugin/archive/refs/tags/v0.2.2-beta.tar.gz

Note that nbgrader installs and enables the jupyter extensions automatically - you may wish to switch off formgrader and create_assignment for non-teachers: YMMV

Configuration

Configuring the nbexchange service

The exchange uses /etc/config/nbexchange_config.py for configuration... though you can override this with the --NbExchange.config_file=<file> parameter on start-up

This is an example config file:

from nbexchange.handlers.auth.user_handler import BaseUserHandler

class MyUserHandler(BaseUserHandler):

    def get_current_user(self, request):
        return {
          "name": "s21100286",
          "full_name": "Joe Bloggs",
          "email": "jb@example.com"
          "lms_user_id" = "5",
          "course_id": "cool_course_id",
          "course_title": "cool course",
          "course_role": "Student",
          "org_id": 1,
    }


c.NbExchange.user_plugin_class = MyUserHandler

c.NbExchange.base_url = /services/exchange
c.NbExchange.base_storage_location = /var/data/exchange/storage
c.NbExchange.db_url = mysql://username:password@my.msql.server.host:3306/db_name

• user_plugin_class

This class performs two roles: Is the user authorised to use the service, and provide some details about the user. Being able to provide user details is taken as an implication of authorisation.

For the exchange to determine how to handle a connection, it needs some details about the user connecting to it. This parameter defines the class that provides the get_current_user method.

You need to write this method for your own application.

Notice that the example above creates the class that provides the method in the config file.

See below for more details on that.

• base_url

This is the url the service listens to. It is essentially the service url used by jupyterhub, and defaults to /services/nbexchange/

• base_storage_location

This is where the exchange will store the files uploaded, and defaults to /tmp/courses

• db_url

This is the database connector, and defaults to an in-memory SQLite (sqlite:///:memory:)

• db_kwargs

Where to include any kwargs to pass to the database connection.

• max_buffer_size

The service will limit the size of uploads. The figure is bytes

By default, upload sizes are limited to 5GB (5253530000)

• upgrade_db, reset_db, debug_db

Do stuff to the db... see the code for what these do

user_plugin_class revisited

For the exchange to work, it needs some details about the user connecting to it - specifically, it looks for 6 pieces of information:

• name: The username of the person (eg perllaghu).
  • Names are indexed, and assumed to be unique.
  • In our system, we prefix the persons login username with the org_id for where their from (eg 1-perllaghu.)
• full_name: The optional full name, if supplied by the remote authenticator.
  • The full name appears in the formgrader UI.
  • nbgrader stores first_name and last_name
• email: An email address for the user, if supplied by the remote authenticator.
  • This is an nbgrader field, nbexchange doesn't use it itself
• lms_user_id: This is the identifier for the user in the LMS/VLE, if supplied by the remote authenticator.
  • This is an nbgrader field, nbexchange doesn't use it itself
  • username to access the system running notebooks is probably not the same as the ID the LMS uses to idnetify the user.
• course_id: The course code as used in nbgrader (eg cool course).
  • This is course_id not course_code, as nbgrader uses course_id for this piece of data.
  • Note that any of the characters {}(){}/\ will give nbgrader a problem [beyond nbexchange]
• course_title: A long name for the course (eg A course of understanding thermondynamics in bulk refrigerant transport).
• course_role: The role of the user, normally Student or Instructor. (currently only Instructor get privilaged actions).
• org_id: As mentioned above, nbexchange divides courses and users across organisations. This is an id (numeric) for the org_id for the user. It defaults to 1 if not given.

Contributing

See how_it_works.md for an extended explanation as to how the exchange works, internally

See Contributing.md for details on how to extend/contribute to the code.

Releasing new versions

• Update pyproject.toml and nbexchange/__init__.py to change to the new version
• Create a new git tag doing git tag -a vx.y.z to match the version above