This is a very large refactoring which aims at making Tutor both more
extendable and more generic. Historically, the Tutor plugin system was
designed as an ad-hoc solution to allow developers to modify their own
Open edX platforms without having to fork Tutor. The plugin API was
simple, but limited, because of its ad-hoc nature. As a consequence,
there were many things that plugin developers could not do, such as
extending different parts of the CLI or adding custom template filters.
Here, we refactor the whole codebase to make use of a generic plugin
system. This system was inspired by the Wordpress plugin API and the
Open edX "hooks and filters" API. The various components are added to a
small core thanks to a set of actions and filters. Actions are callback
functions that can be triggered at different points of the application
lifecycle. Filters are functions that modify some data. Both actions and
filters are collectively named as "hooks". Hooks can optionally be
created within a certain context, which makes it easier to keep track of
which application created which callback.
This new hooks system allows us to provide a Python API that developers
can use to extend their applications. The API reference is added to the
documentation, along with a new plugin development tutorial.
The plugin v0 API remains supported for backward compatibility of
existing plugins.
Done:
- Do not load commands from plugins which are not enabled.
- Load enabled plugins once on start.
- Implement contexts for actions and filters, which allow us to keep track of
the source of every hook.
- Migrate patches
- Migrate commands
- Migrate plugin detection
- Migrate templates_root
- Migrate config
- Migrate template environment globals and filters
- Migrate hooks to tasks
- Generate hook documentation
- Generate patch reference documentation
- Add the concept of action priority
Close #499.
Previously, configuration management was very confusing because we kept mixing
"base" and "defaults" configuration:
- It was difficult to make the difference between core settings that were
necessary (e.g: passwords) as opposed to others that could simply be
defaulted to.
- The order of settings in config.yml mattered: config entries that depended on
other needed to be defined later. As a consequence, Tutor was not compatible
with Python 3.5, where dict entries are not sorted.
When disable a plugin that set config entried, such as the minio plugin, tutor was logging the following:
Disabling plugin minio...
Removed config entry OPENEDX_AWS_ACCESS_KEY=openedx
Removed config entry OPENEDX_AWS_SECRET_ACCESS_KEY={{ MINIO_AWS_SECRET_ACCESS_KEY }}
Plugin disabled
The config values were not rendered during printing, which is a shame, because
the whole point of this log line is to warn users of passwords/secrets that are
being removed. Here, we make sure that the config values are properly rendered.
The new logs are now:
Disabling plugin minio...
Removing config entry OPENEDX_AWS_ACCESS_KEY=openedx
Removing config entry OPENEDX_AWS_SECRET_ACCESS_KEY=64vpCVLxhDxBuNjakSrX4CQg
Plugin disabled
I stumbled upon a bug that should have been detected by the type
checking. Turns out, considering that config is of type Dict[str, Any]
means that we can use just any method on all config values -- which is
terrible. I discovered this after I set `config["PLUGINS"] = None`:
this triggered a crash when I enabled a plugin.
We resolve this by making the Config type more explicit. We also take
the opportunity to remove a few cast statements.
When the PLUGINS config entry is None (`PLUGINS:`), the following error
was being triggered:
File "/.../tutor/tutor/plugins.py",
line 304, in is_enabled
return name in config.get(CONFIG_KEY, [])
TypeError: argument of type 'NoneType' is not iterable
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We are running in strict mode, which is awesome!
This affects a large part of the code base, which might be an issue for
people running a fork of Tutor. Nonetheless, the behavior should not be
affected. If anything, this process has helped find and resolve a few
type-related bugs. Thus, this is not considered as a breaking change.
Tutor was making many calls to iter_installed (~100 on my machine with a
dozen installed plugins). Turns out it's useless to cache Plugin and
Renderer instances, as the config keeps changing all the time. Instead,
we cache the list of installed plugins, which does not change in the
course of a single run.
On my machine this speeds up `tutor config save` by 5x, going from 7.5s
to 1.3s.
Clarify a few variable names, make code more modular. Also, the Renderer
class now makes more sense as a singleton. We took the opportunity to
delete quite a lot of code.
This is for supporting json-based plugins. The great thing about this
change is that it allows us to easily print plugin version numbers in
`plugins list`.
This commit introduces many changes:
- a fully functional minio plugin for local installation
- an almost-functional native k8s deployment
- a new way to process configuration, better suited to plugins
There are still many things to do:
- get rid of all the TODOs
- get a fully functional minio plugin for k8s
- add documentation for pluginso
- ...
