A web framework built on Flask & SQLAlchemy. Somewhere North of Flask but South of Django.
Project description
Keg is an opinionated but flexible web framework built on Flask and SQLAlchemy.
Keg’s Goal
The goal for this project is to encapsulate Flask best practices and libraries so devs can avoid boilerplate and work on the important stuff.
We will lean towards being opinionated on the big things (like SQLAlchemy as our ORM) while supporting hooks and customizations as much as possible.
Think North of Flask but South of Django.
Features
Default Logging Configuration
We highly recommend good logging practices and, as such, a Keg application does basic setup of the Python logging system:
Sets the log level on the root logger to INFO
Creates two handlers and assigns them to the root logger:
outputs to stderr
outputs to syslog
Provides an optional json formatter
The thinking behind that is:
In development, a developer will see log messages on stdout and doesn’t have to monitor a file.
Log messages will be in syslog by default and available for review there if no other action is taken by the developer or sysadmin. This avoids the need to manage log placement, permissions, rotation, etc.
It’s easy to configure syslog daemons to forward log messages to different files or remote log servers and it’s better to handle that type of need at the syslog level than in the app.
Structured log files (json) provide metadata details in a easy-to-parse format and should be easy to generate.
The options and output should be easily configurable from the app to account for different needs in development and deployed scenarios.
Keg’s logging setup should be easy to turn off and/or completely override for situations where it hurts more than it helps.
Installation
pip install keg
App Configuration
CLI Command
The command <myapp> develop config will give detailed information about the files and objects
being used to configure an application.
Profile Priority
All configuration classes with the name DefaultProfile will be applied to the app’s config
first.
Then, the configuration classes that match the “selected” profile will be applied on top of the
app’s existing configuration. This makes the settings from the “selected” profile override any
settings from the DefaultProfile.
Practically speaking, any configuration that applies to the entire app regardless of what context
it is being used in will generally go in myapp.config in the DefaultProfile class.
Selecting a Configuration Profile
The “selected” profile is the name of the objects that the Keg configuration handling code will look for. It should be a string.
A Keg app considers the “selected” profile as follows:
If
config_profilewas passed intomyapp.init()as an argument, use it as the selected profile. The--profilecli option uses this method to set the selected profile and therefore has the highest priority.Look in the app’s environment namespace for “CONFIG_PROFILE”. If found, use it.
If running tests, use “TestProfile”. Whether or not the app is operating in this mode is controlled by the use of:
myapp.init(use_test_profile=True)which is used byMyApp.testing_prep()looking in the app’s environment namespace for “USE_TEST_PROFILE” which is used by
keg.testing.invoke_command()
Look in the app’s main config file (
app.config) and all it’s other config files for the variableDEFAULT_PROFILE. If found, use the value from the file with highest priority.
Views
While generic Flask views will certainly work in this framework, Keg provides a BaseView that
applies a certain amount of magic around route and blueprint setup. BaseView is based on Flask’s
MethodView. Best practice is to set up a blueprint and attach the views to it via the blueprint
attribute. Be aware, BaseView will set up some route, endpoint, and template location defaults,
but these can be configured if needed.
Blueprint Setup
Adding views to a blueprint is accomplished via the blueprint attribute on the view. Note,
BaseView magic kicks in when the class is created, so assigning the blueprint later on will not
currently have the desired effect.
import flask from keg.web import BaseView
blueprint = flask.Blueprint(‘routing’, __name__)
- class VerbRouting(BaseView):
blueprint = blueprint
- def get(self):
return ‘method get’
Once the blueprint is created, you must attach it to the app via the use_blueprints app attribute:
from keg.app import Keg from my_app.views import blueprint
- class MyApp(Keg):
import_name = ‘myapp’ use_blueprints = (blueprint, )
Blueprints take some parameters for URL prefix and template path. BaseView will respect these when generating URLs and finding templates:
- blueprint = flask.Blueprint(
‘custom’, __name__, template_folder=’../templates/specific-path’, url_prefix=’/tanagra’)
- class BlueprintTest(BaseView):
# template “blueprint_test.html” will be expected in specific-path # endpoint is custom.blueprint-test # URL is /tanagra/blueprint-test blueprint = blueprint
- def get(self):
return self.render()
Template Discovery
To avoid requiring the developer to configure all the things, BaseView will attempt to discover the
correct template for a view, based on the view class name. Generally, this is a camel-case to
underscore-notation conversion. Blueprint name is included in the path, unless the blueprint has
its own template_path defined.
class MyBestViewin blueprint named “public” -><app>/templates/public/my_best_view.htmlclass View2in blueprint named “other” with template path “foo” -><app>/foo/view2.html
A view may be given a template_name attribute to override the default filename, although the same
path is used for discovery:
- class TemplateOverride(BaseView):
blueprint = blueprint template_name = ‘my-special-template.html’
- def get(self):
return self.render()
URL and Endpoint Calculation
BaseView has calc_url and calc_endpoint class methods which will allow the developer to avoid
hard-coding those types of values throughout the code. These methods will both produce the full
URL/endpoint, including the blueprint prefix (if any).
Route Generation
BaseView will, by default, create rules for views on their respective blueprints. Generally, this is based on the view class name as a camel-case to dash-notation conversion:
class MyBestViewin blueprint named “public”:/my-best-view->public.my-best-viewclass View2in blueprint named “other” with URL prefix “foo”:/foo/view2->other.view2
Note that BaseView is a MethodView implementation, so methods named get, post, etc. will be
respected as the appropriate targets in the request/response cycle.
A view may be given a url attribute to override the default:
- class RouteOverride(BaseView):
blueprint = blueprint url = ‘/something-other-than-the-default’
- def get(self):
return self.render()
See keg_apps/web/views/routing.py for other routing possibilities that BaseView supports.
Components
Keg components follow the paradigm of flask extensions, and provide some defaults for the purpose of setting up model/view structure. Using components, a project may be broken down into logical blocks, each having their own entities, blueprints, templates, tests, etc.
Components need to be registered in config at
KEG_REGISTERED_COMPONENTSThe path given here should be a full dotted path to the top level of the component
e.g.
my_app.components.blog
At the top level of the component,
__component__must be defined as an instance of KegComponentDepending on the needs of the component, model and view discovery may be driven by the subclasses of KegComponent that have path defaults
Examples:
__component__ = KegModelComponent('blog')__component__ = KegViewComponent('blog')__component__ = KegModelViewComponent('blog')
Component discovery
A component will attempt to load model and blueprints on app init
The default paths relative to the component may be modified or extended on the component’s definition
Default model path in “model” components:
.model.entitiesOverride via the component’s
db_visit_moduleslist of relative import paths
Default blueprint path for “view” components:
.views.component_bpUse the
create_named_blueprintorcreate_blueprinthelpers on the component’s__component__to create blueprints with configured template foldersOverride via the component’s
load_blueprintslistList elements are a tuple of the relative import path and the name of the blueprint attribute
Components have their own template stores, in a
templatesfolderOverride the component’s template path via the
template_folderattribute
Paths may also be supplied to the constructor
e.g.
__component__ = KegComponent('blog', db_visit_modules=('.somewhere.else', ))
Keg Development
To develop on keg, begin by installing dependencies and running the tests:
git clone https://github.com/level12/keg keg-src cd keg-src cp keg_apps/db/user-config-tpl.py ~/.config/keg_apps.db/keg_apps.db-config.py # edit the DB connection info in this file (you don't have to use vim): vim ~/.config/keg_apps.db/keg_apps.db-config.py # Create a virtualenv with a supported python version. Activate it. pip install -e .[tests] pytest keg
You can then examine tox.ini for insights into our development process. In particular, we:
use
pytestfor testing (and coverage analysis)use
flake8for linting
Preview Readme
When updating the readme, use restview --long-description to preview changes.
Links
Documentation: https://keg.readthedocs.io/en/stable/index.html
Releases: https://pypi-hypernode.com/project/Keg/
Issue tracker: https://github.com/level12/keg/issues
Questions & comments: http://groups.google.com/group/blazelibs
Current Status
Stable in a relatively small number of production environments.
API is likely to change with smaller compatibility breaks happening more frequently than larger ones.
Changelog
0.8.9 released 2021-05-07
update python support indicators and drop pathlib dependency (fef7088)
0.8.8 released 2021-04-20
0.8.7 released 2021-02-26
Deprecate KEG_DB_ENGINE_OPTIONS config in favor of Flask-SQLAlchemy’s SQLALCHEMY_ENGINE_OPTIONS (6e1038d)
Remove make_shell_context from app, as the Flask app has that method now since 0.11 (75e4541)
Update db init to create needed schemas from dialect options. Deprecates prep_empty (8def18a)
Allow quiet and verbose CLI options to influence log level (ac5fad6)
Add inrequest decorator and context manager for testing views without full stack (041a0cf)
Link documentation in readme (e12044b)
Allow replacing class view response via pre_response lifecycle method (741c60e)
Support python-dotenv use (1100b39)
0.8.6 released 2021-01-27
BaseView.assign_blueprint allows adding blueprint after class declaration (6f454fc)
Allow returning an empty string as response (96f3e04)
Provide a signal hook db_before_import prior to loading db entities (948ba82)
Add a setting to enforce SQLite foreign key (a7450ba)
Allow blueprint class to be specified for component (78ac281)
Add testing.app_config context manager for injecting config during starting (4b97985)
Resolve failures in config resolution, and provide better reporting in CLI (e9537df)
0.8.5 released 2020-11-25
follow flask namespace recommendations for component blueprint templates (b5d6cf8)
0.8.4 released 2020-05-12
0.8.3 released 2019-11-29
Remove Flask version pin (0b03f12)
0.8.2 released 2019-11-12
fix bug in calculating URL with prefix-less blueprints (7d02b01)
0.8.1 released 2019-11-06
Add basic component structure for app organization into logical blocks (830f93b)
Add
--help-alloption to print out nested tree of app commands (b11fe7e)Clean up view’s use of blueprint attributes to discover templates and calculate URLs/endpoints (949c578)
Limit flask to <1.1.0 until context breakage is resolved (217246f)
0.8.0 released 2019-03-25
0.7.0 released 2019-02-07
Enable setting engine options from KEG variable (5bb807f)
0.6.6 released 2018-11-13
0.6.5 released 2018-05-28
Update readme, start using pipenv, pin Flask < 1.0 (abdc9bf)
0.6.4 released 2018-01-09
when testing, don’t log to syslog by default (304a0a7)
0.6.3 released 2018-01-09
0.6.2 released 2017-12-19
db: get rid of code to replace session object (149b42c)
0.6.1 released 2017-11-16
0.6.0 released 2017-08-18
0.5.1 released 2017-08-15
0.5.0 released 2017-06-27
0.4.1 - 2017-02-09
BUG: Properly quote pgsql identifiers during create (86852ad)
0.4.0 - 2016-12-19
BUG: Properly Update Keyring Config Data (7f1908f)
MSSQL dialect support (df7e89d)
MAINT: Refactor keyring to accept bytes (15bc04b)
MAINT: Remove deprecated flask hooks (4f7e2bf)
Remove unicode_literal futures (dc2fa85)
MAINT: Create windows build environment (983e040)
MAINT: Run CI with Docker (bc7a877)
Remove extra cp in readme (7e94815)
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