In addition to running Open edX in production, Tutor can be used for local development of Open edX. This means that it is possible to hack on Open edX without setting up a Virtual Machine. Essentially, this replaces the devstack provided by edX.
Firstly, either :ref:`install Tutor <install>` (for development against the named releases of Open edX) or :ref:`install Tutor Nightly <nightly>` (for development against Open edX's master branches).
* set ``LMS_HOST`` to `local.overhang.io <http://local.overhang.io>`_ (a convenience domain that simply `points at 127.0.0.1 <https://dnschecker.org/#A/local.overhang.io>`_),
Once first-time setup has been performed with ``launch``, the platform can be started going forward with the lighter-weight ``start -d`` command, which brings up containers *detached* (that is: in the background), but does not perform any initialization tasks::
tutor dev start -d [--mount=./edx-platform]
Or, to start with platform with containers *attached* (that is: in the foreground, the current terminal), omit the ``-d`` flag::
Finally, the platform can also be started back up with ``launch``. It will take longer than ``start``, but it will ensure that config is applied, databases are provisioned & migrated, plugins are fully initialized, and (if applicable) the bind-mounted edx-platform is set up. Notably, ``launch`` is idempotent, so it is always safe to run it again without risk to data. Including the ``--pullimages`` flag will also ensure that container images are up-to-date::
tutor dev launch [--mount=./edx-platform] --pullimages
Debugging with breakpoints
--------------------------
To debug a local edx-platform repository, add a `python breakpoint <https://docs.python.org/3/library/functions.html#breakpoint>`__ with ``breakpoint()`` anywhere in the code. Then, attach to the applicable service's container by running ``start`` (without ``-d``) followed by the service's name::
To run any command inside one of the containers, run ``tutor dev run [OPTIONS] SERVICE [COMMAND] [ARGS]...``. For instance, to open a bash shell in the LMS or CMS containers::
The ``openedx-dev`` Docker image is based on the same ``openedx`` image used by ``tutor local ...`` to run LMS and CMS. However, it has a few differences to make it more convenient for developers:
- The user that runs inside the container has the same UID as the user on the host, to avoid permission problems inside mounted volumes (and in particular in the edx-platform repository).
- Additional Python and system requirements are installed for convenient debugging: `ipython <https://ipython.org/>`__, `ipdb <https://pypi.org/project/ipdb/>`__, vim, telnet.
- The edx-platform `development requirements <https://github.com/openedx/edx-platform/blob/open-release/palm.master/requirements/edx/development.in>`__ are installed.
It may sometimes be convenient to mount container directories on the host, for instance: for editing and debugging. Tutor provides different solutions to this problem.
The ``launch``, ``run``, ``init`` and ``start`` subcommands of ``tutor dev`` and ``tutor local`` support the ``-m/--mount`` option (see :option:`tutor dev start -m`) which can take two different forms. The first is explicit::
tutor dev start --mount=lms:/path/to/edx-platform:/openedx/edx-platform lms
And the second is implicit::
tutor dev start --mount=/path/to/edx-platform lms
With the explicit form, the ``--mount`` option means "bind-mount the host folder /path/to/edx-platform to /openedx/edx-platform in the lms container".
If you use the explicit format, you will quickly realise that you usually want to bind-mount folders in multiple containers at a time. For instance, you will want to bind-mount the edx-platform repository in the "cms" container. To do that, write instead::
tutor dev start --mount=lms,cms:/path/to/edx-platform:/openedx/edx-platform lms
This command line can become cumbersome and inconvenient to work with. But Tutor can be smart about bind-mounting folders to the right containers in the right place when you use the implicit form of the ``--mount`` option. For instance, the following commands are equivalent::
# Explicit form
tutor dev start --mount=lms,lms-worker,lms-job,cms,cms-worker,cms-job:/path/to/edx-platform:/openedx/edx-platform lms
# Implicit form
tutor dev start --mount=/path/to/edx-platform lms
So, when should you *not* be using the implicit form? That would be when Tutor does not know where to bind-mount your host folders. For instance, if you wanted to bind-mount your edx-platform virtual environment located in ``~/venvs/edx-platform``, you should not write ``--mount=~/venvs/edx-platform``, because that folder would be mounted in a way that would override the edx-platform repository in the container. Instead, you should write::
tutor dev start --mount=lms:~/venvs/edx-platform:/openedx/venv lms
..note:: Remember to setup your edx-platform repository for development! See :ref:`edx_platform_dev_env`.
Sometimes, you may want to modify some of the files inside a container for which you don't have a copy on the host. A typical example is when you want to troubleshoot a Python dependency that is installed inside the application virtual environment. In such cases, you want to first copy the contents of the virtual environment from the container to the local filesystem. To that end, Tutor provides the ``tutor dev copyfrom`` command. First, copy the contents of the container folder to the local filesystem::
tutor dev copyfrom lms /openedx/venv ~
Then, bind-mount that folder back in the container with the ``--mount`` option (described :ref:`above <mount_option>`)::
tutor dev start --mount lms:~/venv:/openedx/venv lms
You can then edit the files in ``~/venv`` on your local filesystem and see the changes live in your container.
..warning:: Manually bind-mounting volumes with the ``--volume`` option makes it difficult to simultaneously bind-mount to multiple containers. Also, the ``--volume`` options are not compatible with ``start`` commands. For an alternative, see the :ref:`mount option <mount_option>`.
The above solution may not work for you if you already have an existing directory, outside of the "volumes/" directory, which you would like mounted in one of your containers. For instance, you may want to mount your copy of the `edx-platform <https://github.com/openedx/edx-platform/>`__ repository. In such cases, you can simply use the ``-v/--volume```Docker option <https://docs.docker.com/storage/volumes/#choose-the--v-or---mount-flag>`__::
The above solutions require that you explicitly pass the ``-m/--mount`` options to every ``run``, ``start`` or ``init`` command, which may be inconvenient. To address these issues, you can create a ``docker-compose.override.yml`` file that will specify custom volumes to be used with all ``dev`` commands::
This override file will be loaded when running any ``tutor dev ..`` command. The edx-platform repo mounted at the specified path will be automatically mounted inside all LMS and CMS containers. With this file, you should no longer specify the ``-m/--mount`` option from the command line.
The ``tutor local`` commands load the ``docker-compose.override.yml`` file from the ``$(tutor config printroot)/env/local/docker-compose.override.yml`` directory. One-time jobs from initialisation commands load the ``local/docker-compose.jobs.override.yml`` and ``dev/docker-compose.jobs.override.yml``.
In some cases, you will have to develop features for packages that are pip-installed next to the edx-platform. This is quite easy with Tutor. Just add your packages to the ``$(tutor config printroot)/env/build/openedx/requirements/private.txt`` file. To avoid re-building the openedx Docker image at every change, you should add your package in editable mode. For instance::
You should then run the development server as usual, with ``start``. Every change made to the ``mypackage`` folder will be picked up and the development server will be automatically reloaded.
It's possible to run the full set of unit tests that ship with `edx-platform <https://github.com/openedx/edx-platform/>`__. To do so, run a shell in the LMS development container::
Getting all edx-platform unit tests to pass on Tutor is currently a work-in-progress. Some unit tests are still failing. If you manage to fix some of these, please report your findings in the `Open edX forum <https://discuss.openedx.org/tag/tutor>`__.
