The workflow for converting a chapter

This section proposes a workflow for converting a chapter (or “module”) in a non-Docker A+ course for the Docker version. It assumes that the initialisation described in the previous chapter is completed. See the earlier chapter Instructions in the Programming exercises module for more information.

Add the RST files of the module

  1. Move the RST directory of the next module that is not yet converted from old to the main directory. For example:

    git mv old/python1 python1
    
  2. Add the index file of that module to the main index.rst. In the example below, the module is python1 and its index file is kierros.rst. Delete the A+ manual course modules in that file, or comment them.

    The actual name of the course
    =============================
    
    This index lists an entry for each learning module on course.
    Other content is not visible in A+.
    
    .. toctree::
      :maxdepth: 2
    
      python1/kierros
    
    ..
      m01_introduction/index
      m02_programming_exercises/index
      m03_acos/index
      m04_converting/index
    
  3. Update the :open-time:, :close-time:, and :late-time: for the round in the index file of the module in order to be able to test th exercises. You might want to save the actual deadlines of the last course by commenting them out.

    Ohjelmointi 1
    ^^^^^^^^^^^^^
    
    .. toctree::
      :maxdepth: 1
    
      kurssin_esittely
      python-tutorial-1
      unittest
      python-harjoitukset-1
    
    .. aplusmeta::
      :open-time: 2018-06-01 14:00:00
      :close-time: 2018-08-31 16:00:00
      :late-time: 2018-08-31 23:59:59
    
    ..
      .. aplusmeta::
        :open-time: 2018-01-02 14:00:00
        :close-time: 2018-01-12 16:00:00
        :late-time: 2018-02-28 23:59:59
    
  4. Test the course material: compile RST, then run A+ and mooc-grader.

    ./docker-compile.sh && rm -rf _data && ./docker-up.sh
    

    Check possible compilation errors in the terminal. Then view the course at http://127.0.0.1:8000 in your web browser the usual way. The exercises coded directly in the RST files should work. If they don’t work, the problem is likely either a typo in your RST code or something with the related Sphinx directive in the extensions directory.

Modify exercise grading files

The following is an example of a real Python programming exercise. Notice that you do not need to modify the RST file for updating the exercise for the Docker version of your course.

First, rename current config.yaml file of the exercise to config_old.yaml.

config_old.yaml

view_type: access.types.stdasync.acceptFiles
files:
  - field: file1
    name: laskesumma.py

feedback_template: access/task_direct.html

actions:
  - type: grader.actions.prepare
    charset: UTF-8
    cp_exercises: |
      python1/laskesumma/grader_tests.py->user
      python1/laskesumma/test_config.yaml->user
    expect_success: True

  - type: grader.actions.sandbox_python_test
    cmd: [ "virtualenv.sh", "graderutilsenv", "python3", "-m", "graderutils.main", "test_config.yaml"]
    time: 20
    memory: 500m
    disk: 0
    html: True

Then, create a new config.yaml file. Copy the view_type and files sections from config_old.yaml to this file. NOTE: you don’t need to define a feedback_template anymore if it is a typical template. If you need a specific template, see pull request 19 of mooc-grader.

Write also a new part container:

config.yaml

view_type: access.types.stdasync.acceptFiles
files:
  - field: file1
    name: laskesumma.py

container:
  image: apluslms/grade-python:3.6-2.7
  mount: python1/laskesumma/
  cmd: graderutils
  • The image setting defines the grading container and its version to be used.
  • The mount setting must have the same relative directory path than the actions: cp_exercises setting in config_old.yaml.
  • The cmd setting describes what command is run inside the grading container. By default, use cmd: graderutils, which calls a shell script that does the same than the cmd setting in config_old.yaml. You can also create a run.sh script file (see below); then the line will be cmd: /exercise/run.sh.

You cannot define resource limits, such as execution time and memory, anymore in config.yaml. These must be set in the run.sh script.

run.sh

This is an optional Unix shell script which can be created in the same directory as the exercise config.yaml file and other files. It allows all kinds of additional setup inside the container. Below is a real example from a Python programming exercise “Hunt” from the course Data Structures and Algorithms Y.

The exercise is located at directory exercises/programming/hunt in the course directory. The directory listing in UNIX shell is the following:

t31300-lr124 hunt 1016 % ls -l
total 36
-rw-r--r-- 1 atilante domain users  328 Aug 31 16:22 config.yaml
-rw-r--r-- 1 atilante domain users 3272 May 31 11:22 grader_tests.py
-rw-r--r-- 1 atilante domain users 1518 May 31 11:22 hunt.py
-rw-r--r-- 1 atilante domain users 1615 May 31 11:22 level_generator.py
-rw-r--r-- 1 atilante domain users 2054 May 31 11:22 model.py
-rwxr-xr-x 1 atilante domain users  683 Oct 29 16:19 run.sh*
-rw-r--r-- 1 atilante domain users  521 May 31 11:22 test_config.yaml
drwxr-xr-x 2 atilante domain users 4096 May 31 11:22 testdata/
-rw-r--r-- 1 atilante domain users 1408 May 31 11:22 tests.py
t31300-lr124 hunt 1017 % ls -l testdata
total 28
-rw-r--r-- 1 atilante domain users 2555 May 31 11:22 eldorado.txt
-rw-r--r-- 1 atilante domain users   56 May 31 11:22 gamble.txt
-rw-r--r-- 1 atilante domain users 2554 May 31 11:22 large.txt
-rw-r--r-- 1 atilante domain users   34 May 31 11:22 small2.txt
-rw-r--r-- 1 atilante domain users   62 May 31 11:22 small3.txt
-rw-r--r-- 1 atilante domain users   56 May 31 11:22 small.txt
-rw-r--r-- 1 atilante domain users 2552 May 31 11:22 trapped.txt

As you can see, there are several files.

  • config.yaml is the main configuration file for A+ and mooc-grader.
  • grader_tests.py contains the secret Python unit tests run on the grader.
  • hunt.py is the exercise code template given to the student.
  • level_generator.py is an extra tool used by grader_tests.py.
  • model.py is the model solution for the exercise, used by grader_tests.py.
  • run.sh is the grading script
  • test_config.yaml is the configuration file for Python-grader-utils
  • testdata is a directory containing test inputs given to the student.
  • tests.py has Python unit tests both given to the student and run on the grader.

File config.yaml looks like this:

---
:title: Hunt
description: Ohjelmointitehtävä / Programming exercise

view_type: access.types.stdasync.acceptFiles
files:
  - field: file1
    name: hunt.py
template_files:
  - exercises/programming/hunt/hunt.py

container:
  image: apluslms/grade-python:3.5-2.2
  mount: exercises/programming/hunt
  cmd: /exercise/run.sh

The student must submit one file, which will be saved as /submission/user/hunt.py inside the grading container. template_files tells Radar (plagiarism detector) what parts of code is similar in all student submissions. The cmd setting under container instructs to run the run.sh file, which is located under directory /exercise inside the container.

The contents of run.sh looks like this:

#!/bin/bash

# The working directory is /submission/user which has the user-submitted files
# defined in config.yaml.

# The mount directory from config.yaml is in /exercise (read only).
# Copy files related to unit testing to /submission/user.
cp -r /exercise/testdata .

# 60 seconds of CPU time, 500 MB of virtual memory
ulimit -t 60 -v 524288

# Run python-grader-utils with settings file test_config.yaml.
# The output will be in /feedback/err and /feedback/out
# https://github.com/aalto-letech/python-grader-utils
# https://github.com/apluslms/grade-python
# 120 seconds of wall clock time
timeout 120 graderutils

The comments in the file are quite self-explanatory. The script uses the well-known Bash Unix shell. Essentially, inside the grading container the directory /exercise is the same as the directory exercises/programming/hunt outside the container, and its files are exactly as in the directory listings above. The student has submitted their solution, which is now at /submission/user/hunt.py. When the run.sh begins, the current working directory is /submission/user.

Because this exercise needs test data, those test data files are copied from /exercise/testdata to /submission/user.

ulimit is BASH command; see man bash for details. It sets the CPU time and amount of virtual memory that Python, Python-grader-utils and the student’s program can together use when they are executed.

timeout is part of GNU coreutils and also availabe inside the container. It sets the wall clock time limit for the exercise grading.

As a whole, the script copies test data files to the user submission directory and then executes the graderutils script with 120 seconds of wall clock time, 60 seconds of CPU time and 500 MB of virtual memory.

One should set both the CPU time and wall clock time. The CPU time limits the actual amount of computation that the student’s solution can use. The wall clock time prevents the grading from sleeping forever, like by calling time.sleep() inside the Python program. A rule of thumb is that the wall clock time should be double the CPU time, and the CPU time should be 60 seconds. Note that if you run A+ and mooc-grader on your own computer and test grading of a model solution, the execution time is likely less than on the production server. Moreover, some student solutions which produce valid result might take longer time than the model solution, therefore one minute is a good rule of thumb.

The resource limits are set for extra security. The A+ and mooc-grader running on the servers of Aalto Department of Computer Science have wall clock time limit of some hours for each exercise submission, which is still a limit, but too much in most cases.

Also note that currently, if the CPU or wall clock time limits are hit, the student will only see a message “No grader feedback available for this submission”. This likely causes confusion.

Note that if you create a run.sh file, set the executing permissions. That is, after first time saving the file, give the following command in the exercise directory:

chmod a+x run.sh

If you forget that, when you finally test the exercise, you will see the surprising “No grader feedback available for this submission” error message. Furthermore, if you then inspect the exercise submission in A+, you will see that mooc-grader has given the following feedback:

gw: 18: /gw: /exercise/run.sh: Permission denied
Received exit code 126 from: /exercise/run.sh r2p01
Points '' is not a valid number.
Max points '' is not a valid number."

The “/exercise/run.sh: Permission denied” indicates exactly that you must enable the execution rights for run.sh. See man chmod for details.

Posting submission...