AsyncIO Service-based programming.
|Keywords:||async, service, framework, actors, bootsteps, graph|
What is Mode?
Mode is a library for Python AsyncIO, using the new async/await syntax in Python 3.6 to define your program as a set of services.
When starting a larger project using asyncio, it immediately became apparent that we needed a way to manage the different services running in the program. Questions such as “how do we shutdown the event loop” is frequently answered by telling users to “wait for all coroutines in asyncio.Task.all_tasks”, but we needed more control over what services where stopped, in what order and what services can we safely shutdown without waiting for current operations to complete.
So for us the answer was to create a generic Service class that handles this for us, including creating pretty graphs of active services in the system, and what they are currently doing.
Heavily inspired by Celery/RabbitMQ bootsteps, you could say it’s a less formal version of that, where the graph is built at runtime.
Creating a Service
To define a service, simply subclass and fill in the methods to do stuff as the service is started/stopped etc.:
class MyService(Service): async def on_start(self) -> None: print('Im starting now') async def on_started(self) -> None: print('Im ready') async def on_stop(self) -> None: print('Im stopping now')
To start the service, call await service.start():
Or you can use mode.Worker (or a subclass of this) to start your services-based asyncio program from the console:
if __name__ == '__main__': imoport mode worker = mode.Worker(MyService(), loglevel='INFO', logfile=None) worker.execute_from_commandline()
It’s a Graph!
Services can start other services, coroutines, and background tasks.
Starting other services using add_depenency:
class MyService(Service): def on_init(self) -> None: self.add_dependency(OtherService(loop=self.loop))
Start a list of services using on_init_dependencies:
class MyService(Service): def on_init_dependencies(self) -> None: return [ ServiceA(loop=self.loop), ServiceB(loop=self.loop), ServiceC(loop=self.loop), ]
Start a future/coroutine (that will be waited on to complete on stop):
class MyService(Service): async def on_start(self) -> None: self.add_future(self.my_coro()) async def my_coro(self) -> None: print('Executing coroutine')
Start a background task:
class MyService(Service): @Service.task async def _my_coro(self) -> None: print('Executing coroutine')
Start a background task that keeps running:
class MyService(Service): @Service.task async def _my_coro(self) -> None: while not self.should_stop: # NOTE: self.sleep will wait for one second, or # until service stopped/crashed. await self.sleep(1.0) print('Background thread waking up')
You can install Mode either via the Python Package Index (PyPI) or from source.
To install using pip:
$ pip install -U mode
Downloading and installing from source
Download the latest version of Mode from http://pypi.python.org/pypi/mode
You can install it by doing the following:
$ tar xvfz mode-0.0.0.tar.gz $ cd mode-0.0.0 $ python setup.py build # python setup.py install
The last command must be executed as a privileged user if you are not currently using a virtualenv.
Using the development version
You can install the latest snapshot of Mode using the following pip command:
$ pip install https://github.com/fauststream/Mode/zipball/master#egg=mode
Can I use Mode with Django/Flask/etc.?
Yes! Use gevent/eventlet as a bridge to integrate with asyncio.
This works with any blocking Python library that can work with gevent.
Using gevent requires you to install the aiogevent module, and you can install this as a bundle with Mode:
$ pip install -U mode[gevent]
Then to actually use gevent as the event loop you have to execute the following in your entrypoint module (usually where you start the worker), before any other third party libraries are imported:
#!/usr/bin/env python3 import mode.loop mode.loop.use('gevent') # execute program
REMEMBER: This must be located at the very top of the module, in such a way that it executes before you import other libraries.
This works with any blocking Python library that can work with eventlet.
Using eventlet requires you to install the aioeventlet module, and you can install this as a bundle with Mode:
$ pip install -U mode[eventlet]
Then to actually use eventlet as the event loop you have to execute the following in your entrypoint module (usually where you start the worker), before any other third party libraries are imported:
#!/usr/bin/env python3 import mode.loop mode.loop.use('eventlet') # execute program
REMEMBER: It’s very important this is at the very top of the module, and that it executes before you import libraries.
Can I use Mode with Tornado?
Yes! Use the tornado.platform.asyncio bridge: http://www.tornadoweb.org/en/stable/asyncio.html
Can I use Mode with Twisted?
Yes! Use the asyncio reactor implementation: https://twistedmatrix.com/documents/17.1.0/api/twisted.internet.asyncioreactor.html
Will you support Python 3.5 or earlier?
There are no immediate plans to support Python 3.5, but you are welcome to contribute to the project.
Here are some of the steps required to accomplish this:
Source code transformation to rewrite variable annotations to comments
for example, the code:
class Point: x: int = 0 y: int = 0 must be rewritten into:: class Point: x = 0 # type: int y = 0 # type: int
Source code transformation to rewrite async functions
for example, the code:
async def foo(): await asyncio.sleep(1.0)
must be rewritten into:
@coroutine def foo(): yield from asyncio.sleep(1.0)
Will you support Python 2?
There are no plans to support Python 2, but you are welcome to contribute to the project (details in question above is relevant also for Python 2).
Code of Conduct
Everyone interacting in the project’s codebases, issue trackers, chat rooms, and mailing lists is expected to follow the Mode Code of Conduct.
As contributors and maintainers of these projects, and in the interest of fostering an open and welcoming community, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.
We are committed to making participation in these projects a harassment-free experience for everyone, regardless of level of experience, gender, gender identity and expression, sexual orientation, disability, personal appearance, body size, race, ethnicity, age, religion, or nationality.
Examples of unacceptable behavior by participants include:
- The use of sexualized language or imagery
- Personal attacks
- Trolling or insulting/derogatory comments
- Public or private harassment
- Publishing other’s private information, such as physical or electronic addresses, without explicit permission
- Other unethical or unprofessional conduct.
Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, wiki edits, issues, and other contributions that are not aligned to this Code of Conduct. By adopting this Code of Conduct, project maintainers commit themselves to fairly and consistently applying these principles to every aspect of managing this project. Project maintainers who do not follow or enforce the Code of Conduct may be permanently removed from the project team.
This code of conduct applies both within project spaces and in public spaces when an individual is representing the project or its community.
Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by opening an issue or contacting one or more of the project maintainers.
This Code of Conduct is adapted from the Contributor Covenant, version 1.2.0 available at http://contributor-covenant.org/version/1/2/0/.
Release history Release notifications
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|Filename, size mode-1.9.2.tar.gz (178.2 kB)||File type Source||Python version None||Upload date||Hashes View hashes|