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.
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.
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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.
- 💥[Improvement] Upgrade Open edX to Koa
- 💥 Setting changes:
- The ``ACTIVATE_HTTPS`` setting was renamed to ``ENABLE_HTTPS``.
- Other ``ACTIVATE_*`` variables were all renamed to ``RUN_*``.
- The ``WEB_PROXY`` setting was removed and ``RUN_CADDY`` was added.
- The ``NGINX_HTTPS_PORT`` setting is deprecated.
- Architectural changes:
- Use Caddy as a web proxy for automated SSL/TLS certificate generation:
- Nginx no longer listens to port 443 for https traffic
- The Caddy configuration file comes with a new ``caddyfile`` patch for much simpler SSL/TLS management.
- Configuration files for web proxies are no longer provided.
- Kubernetes deployment no longer requires setting up a custom Ingress resource or custom manager.
- Gunicorn and Whitenoise are replaced by uwsgi: this increases boostrap performance and makes it no longer necessary to mount media folders in the Nginx container.
- Replace memcached and rabbitmq by redis.
- Additional features:
- Make it possible to disable all plugins at once with ``plugins disable all``.
- Add ``tutor k8s wait`` command to wait for a pod to become ready
- Faster, more reliable static assets with local memory caching
- Deprecation: proxy files for Apache and Nginx are no longer provided out of the box.
- Removed plugin `{{ patch (...) }}` statements:
- "https-create", "k8s-ingress-rules", "k8s-ingress-tls-hosts": these are no longer necessary. Instead, declare your app in the "caddyfile" patch.
- "local-docker-compose-nginx-volumes": this patch was primarily used to serve media assets. The recommended is now to serve assets with uwsgi.
Running jobs was previously done with "exec". This was because it
allowed us to avoid copying too much container specification information
from the docker-compose/deployments files to the jobs files. However,
this was limiting:
- In order to run a job, the corresponding container had to be running.
This was particularly painful in Kubernetes, where containers are
crashing as long as migrations are not correctly run.
- Containers in which we need to run jobs needed to be present in the
docker-compose/deployments files. This is unnecessary, for example when
mysql is disabled, or in the case of the certbot container.
Now, we create dedicated jobs files, both for local and k8s deployment.
This introduces a little redundancy, but not too much. Note that
dependent containers are not listed in the docker-compose.jobs.yml file,
so an actual platform is still supposed to be running when we launch the
jobs.
This also introduces a subtle change: now, jobs go through the container
entrypoint prior to running. This is probably a good thing, as it will
avoid forgetting about incorrect environment variables.
In k8s, we find ourselves interacting way too much with the kubectl
utility. Parsing output from the CLI is a pain. So we need to switch to
the native kubernetes client library.
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
- ...
Missing features:
- https certificates
- xqueue
- lms/cms workers
Moreover, we scalability issues due to the uploaded file storage in the
lms/cms. To address this issue we need to develop the MinIO plugin so
that it becomes compatible with Open edX.
Close #126#179#187
Configuration loading was overly complex. Here, we simplify it
drastically with reasonable defaults. Hacky additional variables are
unncessary now that we use custom jinja2 filters.
Régis Behmo
alex.soh