Xqueue external grading system plugin for `Tutor <https://docs.tutor.overhang.io>`_
===================================================================================

This is a plugin for `Tutor <https://docs.tutor.overhang.io>`_ that provides the Xqueue external grading system for Open edX platforms. If you don't know what it is, you probably don't need it.

Installation
------------

The plugin is currently bundled with the `binary releases of Tutor <https://github.com/overhangio/tutor/releases>`__. If you have installed Tutor from source, you will have to install this plugin from source, too::
  
    pip install tutor-xqueue

Then, to enable this plugin, run::
  
    tutor plugins enable xqueue

Usage
-----

In the Open edX studio, edit a course and add a new "Advanced blank problem" ("Problem" 🠆 "Advanced" 🠆  "Advanced blank problem"). Then, click "Edit" and copy-paste the following in the editor::

```
<problem>
  <coderesponse queuename="openedx">
    <label>Write a program that prints "hello world".</label>
    <textbox rows="10" cols="80" mode="python" tabsize="4"/>
    <codeparam>
      <initial_display>
        # students write your program here
        print ""
      </initial_display>
      <answer_display>
        print "hello world"
      </answer_display>
      <grader_payload>
        {"output": "hello world", "max_length": 2}
      </grader_payload>
    </codeparam>
  </coderesponse>
</problem>
```

.. note::
    The queue name must be "openedx".

Save and publish the created unit. Then, access the unit from the LMS and attempt to answer the problem. The answer is sent to the Xqueue service. If you know how to use the Xqueue API, you can access it at http(s)://xqueue.LMS_HOST (in production) or http://xqueue.localhost (in development). However, the Xqueue API is a bit awkward to use. Tutor provides a simple command-line interface to interact with the Xqueue service.

Count the number of submissions that need to be graded::
    
    $ tutor xqueue submissions -u http://xqueue.localhost count
    {
      "content": 0,
      "return_code": 0
    }

.. note::
    By default, ``tutor xqueue submissions`` will hit the Xqueue API running at http(s)://xqueue.LMS_HOST. When running locally, you will want to interact with http://xqueue.localhost. To do so, you should pass the ``--url=http://xqueue.localhost`` option to the CLI.

Show the first submission that should be graded::

    $ tutor xqueue submissions show
    {                                    
      "id": 1,                                                                                                           
      "key": "692c2896cdfc8bdc2d073bc3b3daf928",                    
      "body": {                                                                                                            
        "student_info": "{\"random_seed\": 1, \"anonymous_student_id\": \"af46c9d6c05627aee45257d155ec0b79\", \"submission_time\": \"20200504101653\"}",
        "grader_payload": "\n        {\"output\": \"hello world\", \"max_length\": 2}\n      ",       
        "student_response": "        # students write your program here\r\n        print \"42\"\r\n      "
      },                                                                                            
      "return_code": 0                                         
    }                                                                                              

Grade the submission (in this case, mark it as being correct)::

    $ tutor xqueue submissions grade 1 692c2896cdfc8bdc2d073bc3b3daf928 0.9 true "Good job\!"
    {
      "content": "",
      "return_code": 0
    }

.. warning::
    When running locally, the Xqueue client will report back to the LMS at the production url, so there are great chances that it will not work. A workaround is to manually edit the Submission record stored in the Xqueue database and modify the ``lms_callback_url`` attribute, but this is for advanced users only.

The submission should then appear as correct with the message that you provided on the command line:

.. image:: https://github.com/overhangio/tutor-xqueue/raw/master/screenshots/correctanswer.png
  :alt: Correct answer
  :align: center

Configuration
-------------

- ``XQUEUE_AUTH_PASSWORD`` (default: ``"{{ 8|random_string }}"``)
- ``XQUEUE_AUTH_USERNAME`` (default: ``"lms"``)
- ``XQUEUE_DOCKER_IMAGE`` (default: ``"overhangio/openedx-xqueue:{{ TUTOR_VERSION }}"``)
- ``XQUEUE_HOST`` (default: ``"xqueue.{{ LMS_HOST }}"``)
- ``XQUEUE_MYSQL_PASSWORD`` (default: ``"{{ 8|random_string }}"``)
- ``XQUEUE_MYSQL_DATABASE`` (default: ``"xqueue"``
- ``XQUEUE_MYSQL_USERNAME`` (default: ``"xqueue"``)
- ``XQUEUE_SECRET_KEY`` (default: ``"{{ 24|random_string }}"``)

These values can be modified with ``tutor config save --set PARAM_NAME=VALUE`` commands.