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Converting an existing A+ course to Docker

Introduction and motivation

If you maintain an existing A+ course, and it uses a Python virtual environment (just “virtualenv”), this section describes how to convert it to the Docker environment.

An A+ course not using Docker does not have docker-compile.sh and docker-up.sh scripts. Instead, the course is typically compiled with commands source venv/bin/activate and make html. A Python virtualenv is more like a Python package manager compared to Docker; each virtualenv installs a specific version of Python and specific version of libraries. A+ Docker containers also have that, but moreover, they have all the software preconfigured and ready to use. In contrast, developing a virtualenv A+ course with also A+ and mooc-grader installed on your computer with virtualenv requires extra manual configuration steps. Therefore the aim of A+ Docker containers is to make course development and deployment as easy as possible.

Modifying your git repository

New branch

From now on, this text assumes that you have your current A+ course under git version control.

First, cd to the current directory of your course. Create a new git branch for the Docker version.

git branch docker
git checkout docker

It is recommended to add a to-do document for making the Docker version, for example, Docker-TODO.txt in the main directory.

This is the to-do list for making a Docker version of this course.

TODO
====
- copy files from aplus-manual
- update conf.py
- check RST files
- modify exercise graders

DONE
====

Some people and teams prefer to have their task lists in Trello. Do what suits you best.

Create a directory old and move all the current files into it. This directory will have all the course material which is not yet converted to the Docker version. The idea is to move files back from there in small groups and test them. This way you will easily see what is done, and the rest of the files will not cause Sphinx compilation errors or other trouble.

mkdir old
git mv -k * old

Note that the hidden subdirectory .git, and files .gitignore and .gitmodules will not be moved, as they should.

Commit and push to Github, Aalto Gitlab or whatever git service you have. The --set-upstream option is used only this time; it allows you to later say just git push and it will automatically push your commits to the docker branch on the remote git service.

git commit -m "First commit of Docker version"
git push --set-upstream origin docker

Import apluslms course-templates

There is a minimal code template for a new A+ course using Docker. For your information, the A+ learning management system has its own Github page, and one of the projects there is called course-templates. It has one branch, master, which contains this A+ manual. (The repository used to have more branches for different kinds of examples.) If your course has only exercises and defines the main index.yaml configuration file, you do not need any RST files, Makefile for Sphinx nor the a-plus-rst-tools submodule. If your course has the index.rst file, use a similar structure for the course as the A+ manual has. Download the ZIP file of the branch from Github and extract it to your course directory. Read the README.md file.

(When A+ 1.3 is used,) add directory _data to the .gitignore file of your course. That directory is a write-enabled directory for A+ and mooc-grader which can always be removed. (Starting with A+ 1.4, the _data directory is usually not used anymore. Instead, the run-aplus-front and run-mooc-grader containers should write their data to a data volume, which is set in the docker-compose.yml file.) Add the latest A+ RST tools as a git submodule.

echo _data >> .gitignore
git submodule add https://github.com/Aalto-LeTech/a-plus-rst-tools
git submodule init
git submodule update

Add directory old to exclude_patterns in file conf.py. This way Sphinx will not compile material which is in the old directory.

Note: If your course has custom Sphinx directives, don’t worry. This chapter will describe later how to include them into the Docker version of your course.

# List of patterns, relative to source directory, that match files and
# directories to ignore when looking for source files.
exclude_patterns = ['_build', '_data', 'exercises/solutions', 'old']

Finally, add all new files, commit and push.

git add *
git commit -m "Added A+ course-template"
git push

Congratulations! Now you have all the initial git voodoo done. You have a new branch on your course repository, which has a working copy of the A+ manual and your current course material in the old directory. You can compile the material and run A+ and mooc-grader locally as specified in the introductory module.

Custom Sphinx directives

Your course might have custom Sphinx directives. If you have those, they are probably now in the directory old/extensions the .py files. Some of them might even require A+ RST tools, meaning that they have lines such as from a_plus_rst_tools import aplus_nodes. This section describes how to include those to the Docker version of your course.

Currently, the A+ manual has two custom directives in the extensions subdirectory: bootstrap_styled_topic.py and div.py. Let’s assume the custom Sphinx directives of your course are currently in the directory old/extensions.

  1. If there are Sphinx directives (.py files) with similar name both in extensions and old/extensions, check whether they differ. That can be done with your text editor, or with the command diff extensions/NAME.py old/extensions/NAME.py in the shell; see man diff or the GNU Diffutils page.

    For those files which differ, you need to know which one is more recent and who has modified the file. You might like to try git blame extensions/NAME.py and git blame old/extensions/NAME.py. The git blame command shows for each line of a file when and who has changed it. This might help contacting the authors in case you have not written the Sphinx directives yourself. Finally decide whether to keep the A+ manual version, your version, or merge manually the files.

  2. Custom Sphinx directives not matching step 1 can just be moved to the right place, e.g. git mv old/extensions/NAME.py extensions/NAME.py.

  3. For the custom Sphinx directives which have a couple of from a_plus_rst_tools import in them, chances are you have a symbolic link a-plus-rst-tools in the old/extensions directory, which points to the a_plus_rst_tools subdirectory. That latter directory may have some specific, maybe old version of A+ RST tools. This kind of hack has been made because normally A+ RST tools exists as directory a-plus-rst-tools. This is an invalid Python module name, and therefore the directory has been renamed to a_plus_rst_tools in order to import Python functions from it in the custom Sphinx directive. Moreover, a symbolic link a-plus-rst-tools has been created to it, because A+ RST is cloned from Github by default that name.

    atilante@t31300-lr124 ~/ohj/a-ole/tts
     % cd old/extensions
    atilante@t31300-lr124 ~/ohj/a-ole/tts/old/extensions
     % ls -l
    total 52
    -rw-r--r-- 1 atilante domain users 1273 Jun  5 13:07 aplus_exercise.py
    drwxr-xr-x 5 atilante domain users 4096 Jun  5 13:31 a_plus_rst_tools/
    lrwxrwxrwx 1 atilante domain users   16 Jun  5 13:07 a-plus-rst-tools -> a_plus_rst_tools/
    -rw-r--r-- 1 atilante domain users 4346 Jun  5 13:07 aplus_submit.py
    -rw-r--r-- 1 atilante domain users 2715 Jun  5 13:07 bootstrap_button_collapse.py
    -rw-r--r-- 1 atilante domain users 3487 Jun  5 13:07 bootstrap_panel_table.py
    -rw-r--r-- 1 atilante domain users 1628 Jun  5 13:07 bootstrap_styled_topic.py
    -rw-r--r-- 1 atilante domain users 3147 Jun  5 13:07 div.py
    drwxr-xr-x 2 atilante domain users 4096 Jun  5 13:45 __pycache__/
    -rw-r--r-- 1 atilante domain users 5060 Jun  5 13:07 sql_submit.py
    -rw-r--r-- 1 atilante domain users 1809 Jun  5 13:07 submit_no_tests.py
    -rw-r--r-- 1 atilante domain users 1116 Jun  5 13:07 yaml_extras.py
    

    Likely you want to use the latest A+ RST tools with your custom Sphinx directives. In that case, create a symbolic link from the new extensions directory

    ln -s ../a-plus-rst-tools a_plus_rst_tools
    
  4. As a later development step, you may want to check whether the functionality of your custom Sphinx directives is actually included in the latest A+ RST tools.

Merging conf.py

Next you will have to merge old/conf.py to conf.py. Copy lines from the former to the latter. Run ./docker-compile.sh to ensure that nothing has broken.

Possible errors encountered

Extension error:
Could not import extension my_directive (exception: No module named 'my_directive')
Makefile:60: recipe for target 'html' failed
make: *** [html] Error 1

You have my_directive in conf.py in the list extensions, but Sphinx cannot find it. Have you moved the file to the right directory? Sphinx can only find custom directives from directories which are declared in conf.py with sys.path.append. For example, if you need to place your directive into directory extensions/mydir, put the following into conf.py:

sys.path.append(os.path.abspath('extensions/mydir'))
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