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Andrew Godwin 2015-06-20 10:27:22 +08:00
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.gitignore vendored
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*.egg-info
dist/
docs/_build

30
channels/backends/base.py
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@ -61,5 +61,35 @@ class BaseChannelBackend(object):
continue
return channel, message
def group_add(self, group, channel, expiry=None):
"""
Adds the channel to the named group for at least 'expiry'
seconds (expiry defaults to message expiry if not provided).
"""
raise NotImplementedError()
def group_discard(self, group, channel):
"""
Removes the channel from the named group if it is in the group;
does nothing otherwise (does not error)
"""
raise NotImplementedError()
def group_channels(self, group):
"""
Returns an iterable of all channels in the group.
"""
raise NotImplementedError()
def send_group(self, group, message):
"""
Sends a message to the entire group.
This base class provides a default implementation; can be overridden
to be more efficient by subclasses.
"""
for channel in self.group_channels():
self.send(channel, message)
def __str__(self):
return self.__class__.__name__

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docs/Makefile Normal file
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# Makefile for Sphinx documentation
#
# You can set these variables from the command line.
SPHINXOPTS =
SPHINXBUILD = sphinx-build
PAPER =
BUILDDIR = _build
# User-friendly check for sphinx-build
ifeq ($(shell which $(SPHINXBUILD) >/dev/null 2>&1; echo $$?), 1)
$(error The '$(SPHINXBUILD)' command was not found. Make sure you have Sphinx installed, then set the SPHINXBUILD environment variable to point to the full path of the '$(SPHINXBUILD)' executable. Alternatively you can add the directory with the executable to your PATH. If you don't have Sphinx installed, grab it from http://sphinx-doc.org/)
endif
# Internal variables.
PAPEROPT_a4 = -D latex_paper_size=a4
PAPEROPT_letter = -D latex_paper_size=letter
ALLSPHINXOPTS = -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
# the i18n builder cannot share the environment and doctrees with the others
I18NSPHINXOPTS = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
.PHONY: help clean html dirhtml singlehtml pickle json htmlhelp qthelp devhelp epub latex latexpdf text man changes linkcheck doctest gettext
help:
@echo "Please use \`make <target>' where <target> is one of"
@echo " html to make standalone HTML files"
@echo " dirhtml to make HTML files named index.html in directories"
@echo " singlehtml to make a single large HTML file"
@echo " pickle to make pickle files"
@echo " json to make JSON files"
@echo " htmlhelp to make HTML files and a HTML help project"
@echo " qthelp to make HTML files and a qthelp project"
@echo " devhelp to make HTML files and a Devhelp project"
@echo " epub to make an epub"
@echo " latex to make LaTeX files, you can set PAPER=a4 or PAPER=letter"
@echo " latexpdf to make LaTeX files and run them through pdflatex"
@echo " latexpdfja to make LaTeX files and run them through platex/dvipdfmx"
@echo " text to make text files"
@echo " man to make manual pages"
@echo " texinfo to make Texinfo files"
@echo " info to make Texinfo files and run them through makeinfo"
@echo " gettext to make PO message catalogs"
@echo " changes to make an overview of all changed/added/deprecated items"
@echo " xml to make Docutils-native XML files"
@echo " pseudoxml to make pseudoxml-XML files for display purposes"
@echo " linkcheck to check all external links for integrity"
@echo " doctest to run all doctests embedded in the documentation (if enabled)"
clean:
rm -rf $(BUILDDIR)/*
html:
$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
@echo
@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."
dirhtml:
$(SPHINXBUILD) -b dirhtml $(ALLSPHINXOPTS) $(BUILDDIR)/dirhtml
@echo
@echo "Build finished. The HTML pages are in $(BUILDDIR)/dirhtml."
singlehtml:
$(SPHINXBUILD) -b singlehtml $(ALLSPHINXOPTS) $(BUILDDIR)/singlehtml
@echo
@echo "Build finished. The HTML page is in $(BUILDDIR)/singlehtml."
pickle:
$(SPHINXBUILD) -b pickle $(ALLSPHINXOPTS) $(BUILDDIR)/pickle
@echo
@echo "Build finished; now you can process the pickle files."
json:
$(SPHINXBUILD) -b json $(ALLSPHINXOPTS) $(BUILDDIR)/json
@echo
@echo "Build finished; now you can process the JSON files."
htmlhelp:
$(SPHINXBUILD) -b htmlhelp $(ALLSPHINXOPTS) $(BUILDDIR)/htmlhelp
@echo
@echo "Build finished; now you can run HTML Help Workshop with the" \
".hhp project file in $(BUILDDIR)/htmlhelp."
qthelp:
$(SPHINXBUILD) -b qthelp $(ALLSPHINXOPTS) $(BUILDDIR)/qthelp
@echo
@echo "Build finished; now you can run "qcollectiongenerator" with the" \
".qhcp project file in $(BUILDDIR)/qthelp, like this:"
@echo "# qcollectiongenerator $(BUILDDIR)/qthelp/Channels.qhcp"
@echo "To view the help file:"
@echo "# assistant -collectionFile $(BUILDDIR)/qthelp/Channels.qhc"
devhelp:
$(SPHINXBUILD) -b devhelp $(ALLSPHINXOPTS) $(BUILDDIR)/devhelp
@echo
@echo "Build finished."
@echo "To view the help file:"
@echo "# mkdir -p $$HOME/.local/share/devhelp/Channels"
@echo "# ln -s $(BUILDDIR)/devhelp $$HOME/.local/share/devhelp/Channels"
@echo "# devhelp"
epub:
$(SPHINXBUILD) -b epub $(ALLSPHINXOPTS) $(BUILDDIR)/epub
@echo
@echo "Build finished. The epub file is in $(BUILDDIR)/epub."
latex:
$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
@echo
@echo "Build finished; the LaTeX files are in $(BUILDDIR)/latex."
@echo "Run \`make' in that directory to run these through (pdf)latex" \
"(use \`make latexpdf' here to do that automatically)."
latexpdf:
$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
@echo "Running LaTeX files through pdflatex..."
$(MAKE) -C $(BUILDDIR)/latex all-pdf
@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
latexpdfja:
$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
@echo "Running LaTeX files through platex and dvipdfmx..."
$(MAKE) -C $(BUILDDIR)/latex all-pdf-ja
@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
text:
$(SPHINXBUILD) -b text $(ALLSPHINXOPTS) $(BUILDDIR)/text
@echo
@echo "Build finished. The text files are in $(BUILDDIR)/text."
man:
$(SPHINXBUILD) -b man $(ALLSPHINXOPTS) $(BUILDDIR)/man
@echo
@echo "Build finished. The manual pages are in $(BUILDDIR)/man."
texinfo:
$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
@echo
@echo "Build finished. The Texinfo files are in $(BUILDDIR)/texinfo."
@echo "Run \`make' in that directory to run these through makeinfo" \
"(use \`make info' here to do that automatically)."
info:
$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
@echo "Running Texinfo files through makeinfo..."
make -C $(BUILDDIR)/texinfo info
@echo "makeinfo finished; the Info files are in $(BUILDDIR)/texinfo."
gettext:
$(SPHINXBUILD) -b gettext $(I18NSPHINXOPTS) $(BUILDDIR)/locale
@echo
@echo "Build finished. The message catalogs are in $(BUILDDIR)/locale."
changes:
$(SPHINXBUILD) -b changes $(ALLSPHINXOPTS) $(BUILDDIR)/changes
@echo
@echo "The overview file is in $(BUILDDIR)/changes."
linkcheck:
$(SPHINXBUILD) -b linkcheck $(ALLSPHINXOPTS) $(BUILDDIR)/linkcheck
@echo
@echo "Link check complete; look for any errors in the above output " \
"or in $(BUILDDIR)/linkcheck/output.txt."
doctest:
$(SPHINXBUILD) -b doctest $(ALLSPHINXOPTS) $(BUILDDIR)/doctest
@echo "Testing of doctests in the sources finished, look at the " \
"results in $(BUILDDIR)/doctest/output.txt."
xml:
$(SPHINXBUILD) -b xml $(ALLSPHINXOPTS) $(BUILDDIR)/xml
@echo
@echo "Build finished. The XML files are in $(BUILDDIR)/xml."
pseudoxml:
$(SPHINXBUILD) -b pseudoxml $(ALLSPHINXOPTS) $(BUILDDIR)/pseudoxml
@echo
@echo "Build finished. The pseudo-XML files are in $(BUILDDIR)/pseudoxml."

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Channel Backend Requirements
============================
While the channel backends are pluggable, there's a minimum standard they
must meet in terms of the way they perform.
In particular, a channel backend MUST:
* Provide a ``send()`` method which sends a message onto a named channel
* Provide a ``receive_many()`` method which returns an available message on the
provided channels, or returns no message either instantly or after a short
delay (it must not block indefinitely)
* Provide a ``group_add()`` method which adds a channel to a named group
for at least the provided expiry period.
* Provide a ``group_discard()`` method with removes a channel from a named
group if it was added, and nothing otherwise.
* Provide a ``group_members()`` method which returns an iterable of all
channels currently in the group.
* Preserve the ordering of messages inside a channel
* Never deliver a message more than once
* Never block on sending of a message (dropping the message/erroring is preferable to blocking)
* Be able to store messages of at least 5MB in size
* Expire messages only after the expiry period provided is up (a backend may
keep them longer if it wishes, but should expire them at some reasonable
point to ensure users do not come to rely on permanent messages)
In addition, it SHOULD:
* Provide a ``receive_many_blocking()`` method which is like ``receive_many()``
but blocks until a message is available.
* Provide a ``send_group()`` method which sends a message to every channel
in a group.
* Try and preserve a rough global ordering, so that one busy channel does not
drown out an old message in another channel if a worker is listening on both.

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docs/concepts.rst Normal file
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Concepts
========
Django's traditional view of the world revolves around requests and responses;
a request comes in, Django is fired up to serve it, generates a response to
send, and then Django goes away and waits for the next request.
That was fine when the internet was all driven by simple browser interactions,
but the modern Web includes things like WebSockets and HTTP2 server push,
which allow websites to communicate outside of this traditional cycle.
And, beyond that, there are plenty of non-critical tasks that applications
could easily offload until after a response as been sent - like saving things
into a cache, or thumbnailing newly-uploaded images.
Channels changes the way Django runs to be "event oriented" - rather than
just responding to requests, instead Django responses to a wide array of events
sent on *channels*. There's still no persistent state - each event handler,
or *consumer* as we call them, is called independently in a way much like a
view is called.
Let's look at what *channels* are first.
What is a channel?
------------------
The core of Channels is, unsurprisingly, a datastructure called a *channel*.
What is a channel? It is an *ordered*, *first-in first-out queue* with
*at-most-once delivery* to *only one listener at a time*.
You can think of it as analagous to a task queue - messages are put onto
the channel by *producers*, and then given to just one of the *consumers*
listening to that channnel.
By *at-most-once* we say that either one consumer gets the message or nobody
does (if the channel implementation crashes, let's say). The
alternative is *at-least-once*, where normally one consumer gets the message
but when things crash it's sent to more than one, which is not the trade-off
we want.
There are a couple of other limitations - messages must be JSON-serialisable,
and not be more than 1MB in size - but these are to make the whole thing
practical, and not too important to think about up front.
The channels have capacity, so a load of producers can write lots of messages
into a channel with no consumers and then a consumer can come along later and
will start getting served those queued messages.
If you've used channels in Go, these are reasonably similar to those. The key
difference is that these channels are network-transparent; the implementations
of channels we provide are all accessible across a network to consumers
and producers running in different processes or on different machines.
Inside a network, we identify channels uniquely by a name string - you can
send to any named channel from any machine connected to the same channel
backend. If two different machines both write to the ``django.wsgi.request``
channel, they're writing into the same channel.
How do we use channels?
-----------------------
That's what a channel is, but how is Django using them? Well, inside Django
you can connect a function to consume a channel, like so::
@Channel.consumer("channel-name")
def my_consumer(something, **kwargs):
pass
This means that for every message on the channel, Django will call that
consumer function with the message as keyword arguments (messages are always
a dict, and are mapped to keyword arguments for send/receive).
Django can do this as rather than run in a request-response mode, Channels
changes Django so that it runs in a worker mode - it listens on all channels
that have consumers declared, and when a message arrives on one, runs the
relevant consumer.
In fact, this is illustrative of the new way Django runs to enable Channels to
work. Rather than running in just a single process tied to a WSGI server,
Django runs in three separate layers:
* Interface servers, which communicate between Django and the outside world.
This includes a WSGI adapter as well as a separate WebSocket server - we'll
cover this later.
* The channel backend, which is a combination of pluggable Python code and
a datastore (a database, or Redis) and responsible for transporting messages.
* The workers, that listen on all relevant channels and run consumer code
when a message is ready.
This may seem quite simplistic, but that's part of the design; rather than
try and have a full asynchronous architecture, we're just introducing a
slightly more complex abstraction than that presented by Django views.
A view takes a request and returns a response; a consumer takes a channel
message and can write out zero to many other channel messages.
Now, let's make a channel for requests (called ``django.wsgi.request``),
and a channel per client for responses (e.g. ``django.wsgi.respsonse.o4F2h2Fd``),
with the response channel a property (``send_channel``) of the request message.
Suddenly, a view is merely another example of a consumer::
@Channel.consumer("django.wsgi.request")
def my_consumer(send_channel, **request_data):
# Decode the request from JSON-compat to a full object
django_request = Request.decode(request_data)
# Run view
django_response = view(django_request)
# Encode the response into JSON-compat format
Channel(send_channel).send(django_response.encode())
In fact, this is how Channels works. The interface servers transform connections
from the outside world (HTTP, WebSockets, etc.) into messages on channels,
and then you write workers to handle these messages.
This may seem like it's still not very well designed to handle push-style
code - where you use HTTP2's server-sent events or a WebSocket to notify
clients of changes in real time (messages in a chat, perhaps, or live updates
in an admin as another user edits something).
However, the key here is that you can run code (and so send on channels) in
response to any event - and that includes ones you create. You can trigger
on model saves, on other incoming messages, or from code paths inside views
and forms.
.. _channel-types:
Channel Types
-------------
Now, if you think about it, there are actually two major uses for channels in
this model. The first, and more obvious one, is the dispatching of work to
consumers - a message gets added to a channel, and then any one of the workers
can pick it up and run the consumer.
The second kind of channel, however, is used for responses. Notably, these only
have one thing listening on them - the interface server. Each response channel
is individually named and has to be routed back to the interface server where
its client is terminated.
This is not a massive difference - they both still behave according to the core
definition of a *channel* - but presents some problems when we're looking to
scale things up. We can happily randomly load-balance normal channels across
clusters of channel servers and workers - after all, any worker can process
the message - but response channels would have to have their messages sent
to the channel server they're listening on.
For this reason, Channels treats these as two different *channel types*, and
denotes a response channel by having the first character of the channel name
be the character ``!`` - e.g. ``!django.wsgi.response.f5G3fE21f``. Normal
channels have no special prefix, but along with the rest of the response
channel name, they must contain only the characters ``a-z A-Z 0-9 - _``,
and be less than 200 characters long.
It's optional for a backend implementation to understand this - after all,
it's only important at scale, where you want to shard the two types differently
- but it's present nonetheless. For more on scaling, and how to handle channel
types if you're writing a backend or interface server, read :doc:`scaling`.
Groups
------
Because channels only deliver to a single listener, they can't do broadcast;
if you want to send a message to an arbitrary group of clients, you need to
keep track of which response channels of those you wish to send to.
Say I had a live blog where I wanted to push out updates whenever a new post is
saved, I would register a handler for the ``post_save`` signal and keep a
set of channels to send updates to::
(todo)

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# -*- coding: utf-8 -*-
#
# Channels documentation build configuration file, created by
# sphinx-quickstart on Fri Jun 19 11:37:58 2015.
#
# This file is execfile()d with the current directory set to its
# containing dir.
#
# Note that not all possible configuration values are present in this
# autogenerated file.
#
# All configuration values have a default; values that are commented out
# serve to show the default.
import sys
import os
# If extensions (or modules to document with autodoc) are in another directory,
# add these directories to sys.path here. If the directory is relative to the
# documentation root, use os.path.abspath to make it absolute, like shown here.
#sys.path.insert(0, os.path.abspath('.'))
# -- General configuration ------------------------------------------------
# If your documentation needs a minimal Sphinx version, state it here.
#needs_sphinx = '1.0'
# Add any Sphinx extension module names here, as strings. They can be
# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
# ones.
extensions = []
# Add any paths that contain templates here, relative to this directory.
templates_path = ['_templates']
# The suffix of source filenames.
source_suffix = '.rst'
# The encoding of source files.
#source_encoding = 'utf-8-sig'
# The master toctree document.
master_doc = 'index'
# General information about the project.
project = u'Channels'
copyright = u'2015, Andrew Godwin'
# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
# built documents.
#
# The short X.Y version.
version = '0.2'
# The full version, including alpha/beta/rc tags.
release = '0.2'
# The language for content autogenerated by Sphinx. Refer to documentation
# for a list of supported languages.
#language = None
# There are two options for replacing |today|: either, you set today to some
# non-false value, then it is used:
#today = ''
# Else, today_fmt is used as the format for a strftime call.
#today_fmt = '%B %d, %Y'
# List of patterns, relative to source directory, that match files and
# directories to ignore when looking for source files.
exclude_patterns = ['_build']
# The reST default role (used for this markup: `text`) to use for all
# documents.
#default_role = None
# If true, '()' will be appended to :func: etc. cross-reference text.
#add_function_parentheses = True
# If true, the current module name will be prepended to all description
# unit titles (such as .. function::).
#add_module_names = True
# If true, sectionauthor and moduleauthor directives will be shown in the
# output. They are ignored by default.
#show_authors = False
# The name of the Pygments (syntax highlighting) style to use.
pygments_style = 'sphinx'
# A list of ignored prefixes for module index sorting.
#modindex_common_prefix = []
# If true, keep warnings as "system message" paragraphs in the built documents.
#keep_warnings = False
# -- Options for HTML output ----------------------------------------------
# The theme to use for HTML and HTML Help pages. See the documentation for
# a list of builtin themes.
html_theme = 'default'
# Theme options are theme-specific and customize the look and feel of a theme
# further. For a list of options available for each theme, see the
# documentation.
#html_theme_options = {}
# Add any paths that contain custom themes here, relative to this directory.
#html_theme_path = []
# The name for this set of Sphinx documents. If None, it defaults to
# "<project> v<release> documentation".
#html_title = None
# A shorter title for the navigation bar. Default is the same as html_title.
#html_short_title = None
# The name of an image file (relative to this directory) to place at the top
# of the sidebar.
#html_logo = None
# The name of an image file (within the static path) to use as favicon of the
# docs. This file should be a Windows icon file (.ico) being 16x16 or 32x32
# pixels large.
#html_favicon = None
# Add any paths that contain custom static files (such as style sheets) here,
# relative to this directory. They are copied after the builtin static files,
# so a file named "default.css" will overwrite the builtin "default.css".
html_static_path = ['_static']
# Add any extra paths that contain custom files (such as robots.txt or
# .htaccess) here, relative to this directory. These files are copied
# directly to the root of the documentation.
#html_extra_path = []
# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
# using the given strftime format.
#html_last_updated_fmt = '%b %d, %Y'
# If true, SmartyPants will be used to convert quotes and dashes to
# typographically correct entities.
#html_use_smartypants = True
# Custom sidebar templates, maps document names to template names.
#html_sidebars = {}
# Additional templates that should be rendered to pages, maps page names to
# template names.
#html_additional_pages = {}
# If false, no module index is generated.
#html_domain_indices = True
# If false, no index is generated.
#html_use_index = True
# If true, the index is split into individual pages for each letter.
#html_split_index = False
# If true, links to the reST sources are added to the pages.
#html_show_sourcelink = True
# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
#html_show_sphinx = True
# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
#html_show_copyright = True
# If true, an OpenSearch description file will be output, and all pages will
# contain a <link> tag referring to it. The value of this option must be the
# base URL from which the finished HTML is served.
#html_use_opensearch = ''
# This is the file name suffix for HTML files (e.g. ".xhtml").
#html_file_suffix = None
# Output file base name for HTML help builder.
htmlhelp_basename = 'Channelsdoc'
# -- Options for LaTeX output ---------------------------------------------
latex_elements = {
# The paper size ('letterpaper' or 'a4paper').
#'papersize': 'letterpaper',
# The font size ('10pt', '11pt' or '12pt').
#'pointsize': '10pt',
# Additional stuff for the LaTeX preamble.
#'preamble': '',
}
# Grouping the document tree into LaTeX files. List of tuples
# (source start file, target name, title,
# author, documentclass [howto, manual, or own class]).
latex_documents = [
('index', 'Channels.tex', u'Channels Documentation',
u'Andrew Godwin', 'manual'),
]
# The name of an image file (relative to this directory) to place at the top of
# the title page.
#latex_logo = None
# For "manual" documents, if this is true, then toplevel headings are parts,
# not chapters.
#latex_use_parts = False
# If true, show page references after internal links.
#latex_show_pagerefs = False
# If true, show URL addresses after external links.
#latex_show_urls = False
# Documents to append as an appendix to all manuals.
#latex_appendices = []
# If false, no module index is generated.
#latex_domain_indices = True
# -- Options for manual page output ---------------------------------------
# One entry per manual page. List of tuples
# (source start file, name, description, authors, manual section).
man_pages = [
('index', 'channels', u'Channels Documentation',
[u'Andrew Godwin'], 1)
]
# If true, show URL addresses after external links.
#man_show_urls = False
# -- Options for Texinfo output -------------------------------------------
# Grouping the document tree into Texinfo files. List of tuples
# (source start file, target name, title, author,
# dir menu entry, description, category)
texinfo_documents = [
('index', 'Channels', u'Channels Documentation',
u'Andrew Godwin', 'Channels', 'One line description of project.',
'Miscellaneous'),
]
# Documents to append as an appendix to all manuals.
#texinfo_appendices = []
# If false, no module index is generated.
#texinfo_domain_indices = True
# How to display URL addresses: 'footnote', 'no', or 'inline'.
#texinfo_show_urls = 'footnote'
# If true, do not generate a @detailmenu in the "Top" node's menu.
#texinfo_no_detailmenu = False

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Getting Started
===============
(If you haven't yet, make sure you :doc:`install Channels <installation>`
and read up on :doc:`the concepts behind Channels <concepts>`)

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Django Channels
===============
Channels is a project to make Django able to handle more than just plain
HTTP requests, including WebSockets and HTTP2, as well as the ability to
run code after a response has been sent for things like thumbnailing or
background calculation.
It's an easy-to-understand extension of the Django view model, and easy
to integrate and deploy.
First, read our :doc:`concepts` documentation to get an idea of the
data model underlying Channels and how they're used inside Django.
Then, read :doc:`getting-started` to see how to get up and running with
WebSockets with only 30 lines of code.
Contents:
.. toctree::
:maxdepth: 2
concepts
installation
getting-started
integration-changes
message-standards
scaling
backend-requirements

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docs/installation.rst Normal file
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Installation
============
Channels is available on PyPI - to install it, just run::
pip install -U channels
Once that's done, you should add ``channels`` to your
``INSTALLED_APPS`` setting::
INSTALLED_APPS = (
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
...
'channels',
)
That's it! Once enabled, ``channels`` will integrate itself into Django and
take control of the ``runserver`` command. See :doc:`getting-started` for more.

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channels/docs/integration-changes.rst → docs/integration-changes.rst
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@ECHO OFF
REM Command file for Sphinx documentation
if "%SPHINXBUILD%" == "" (
set SPHINXBUILD=sphinx-build
)
set BUILDDIR=_build
set ALLSPHINXOPTS=-d %BUILDDIR%/doctrees %SPHINXOPTS% .
set I18NSPHINXOPTS=%SPHINXOPTS% .
if NOT "%PAPER%" == "" (
set ALLSPHINXOPTS=-D latex_paper_size=%PAPER% %ALLSPHINXOPTS%
set I18NSPHINXOPTS=-D latex_paper_size=%PAPER% %I18NSPHINXOPTS%
)
if "%1" == "" goto help
if "%1" == "help" (
:help
echo.Please use `make ^<target^>` where ^<target^> is one of
echo. html to make standalone HTML files
echo. dirhtml to make HTML files named index.html in directories
echo. singlehtml to make a single large HTML file
echo. pickle to make pickle files
echo. json to make JSON files
echo. htmlhelp to make HTML files and a HTML help project
echo. qthelp to make HTML files and a qthelp project
echo. devhelp to make HTML files and a Devhelp project
echo. epub to make an epub
echo. latex to make LaTeX files, you can set PAPER=a4 or PAPER=letter
echo. text to make text files
echo. man to make manual pages
echo. texinfo to make Texinfo files
echo. gettext to make PO message catalogs
echo. changes to make an overview over all changed/added/deprecated items
echo. xml to make Docutils-native XML files
echo. pseudoxml to make pseudoxml-XML files for display purposes
echo. linkcheck to check all external links for integrity
echo. doctest to run all doctests embedded in the documentation if enabled
goto end
)
if "%1" == "clean" (
for /d %%i in (%BUILDDIR%\*) do rmdir /q /s %%i
del /q /s %BUILDDIR%\*
goto end
)
%SPHINXBUILD% 2> nul
if errorlevel 9009 (
echo.
echo.The 'sphinx-build' command was not found. Make sure you have Sphinx
echo.installed, then set the SPHINXBUILD environment variable to point
echo.to the full path of the 'sphinx-build' executable. Alternatively you
echo.may add the Sphinx directory to PATH.
echo.
echo.If you don't have Sphinx installed, grab it from
echo.http://sphinx-doc.org/
exit /b 1
)
if "%1" == "html" (
%SPHINXBUILD% -b html %ALLSPHINXOPTS% %BUILDDIR%/html
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The HTML pages are in %BUILDDIR%/html.
goto end
)
if "%1" == "dirhtml" (
%SPHINXBUILD% -b dirhtml %ALLSPHINXOPTS% %BUILDDIR%/dirhtml
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The HTML pages are in %BUILDDIR%/dirhtml.
goto end
)
if "%1" == "singlehtml" (
%SPHINXBUILD% -b singlehtml %ALLSPHINXOPTS% %BUILDDIR%/singlehtml
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The HTML pages are in %BUILDDIR%/singlehtml.
goto end
)
if "%1" == "pickle" (
%SPHINXBUILD% -b pickle %ALLSPHINXOPTS% %BUILDDIR%/pickle
if errorlevel 1 exit /b 1
echo.
echo.Build finished; now you can process the pickle files.
goto end
)
if "%1" == "json" (
%SPHINXBUILD% -b json %ALLSPHINXOPTS% %BUILDDIR%/json
if errorlevel 1 exit /b 1
echo.
echo.Build finished; now you can process the JSON files.
goto end
)
if "%1" == "htmlhelp" (
%SPHINXBUILD% -b htmlhelp %ALLSPHINXOPTS% %BUILDDIR%/htmlhelp
if errorlevel 1 exit /b 1
echo.
echo.Build finished; now you can run HTML Help Workshop with the ^
.hhp project file in %BUILDDIR%/htmlhelp.
goto end
)
if "%1" == "qthelp" (
%SPHINXBUILD% -b qthelp %ALLSPHINXOPTS% %BUILDDIR%/qthelp
if errorlevel 1 exit /b 1
echo.
echo.Build finished; now you can run "qcollectiongenerator" with the ^
.qhcp project file in %BUILDDIR%/qthelp, like this:
echo.^> qcollectiongenerator %BUILDDIR%\qthelp\Channels.qhcp
echo.To view the help file:
echo.^> assistant -collectionFile %BUILDDIR%\qthelp\Channels.ghc
goto end
)
if "%1" == "devhelp" (
%SPHINXBUILD% -b devhelp %ALLSPHINXOPTS% %BUILDDIR%/devhelp
if errorlevel 1 exit /b 1
echo.
echo.Build finished.
goto end
)
if "%1" == "epub" (
%SPHINXBUILD% -b epub %ALLSPHINXOPTS% %BUILDDIR%/epub
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The epub file is in %BUILDDIR%/epub.
goto end
)
if "%1" == "latex" (
%SPHINXBUILD% -b latex %ALLSPHINXOPTS% %BUILDDIR%/latex
if errorlevel 1 exit /b 1
echo.
echo.Build finished; the LaTeX files are in %BUILDDIR%/latex.
goto end
)
if "%1" == "latexpdf" (
%SPHINXBUILD% -b latex %ALLSPHINXOPTS% %BUILDDIR%/latex
cd %BUILDDIR%/latex
make all-pdf
cd %BUILDDIR%/..
echo.
echo.Build finished; the PDF files are in %BUILDDIR%/latex.
goto end
)
if "%1" == "latexpdfja" (
%SPHINXBUILD% -b latex %ALLSPHINXOPTS% %BUILDDIR%/latex
cd %BUILDDIR%/latex
make all-pdf-ja
cd %BUILDDIR%/..
echo.
echo.Build finished; the PDF files are in %BUILDDIR%/latex.
goto end
)
if "%1" == "text" (
%SPHINXBUILD% -b text %ALLSPHINXOPTS% %BUILDDIR%/text
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The text files are in %BUILDDIR%/text.
goto end
)
if "%1" == "man" (
%SPHINXBUILD% -b man %ALLSPHINXOPTS% %BUILDDIR%/man
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The manual pages are in %BUILDDIR%/man.
goto end
)
if "%1" == "texinfo" (
%SPHINXBUILD% -b texinfo %ALLSPHINXOPTS% %BUILDDIR%/texinfo
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The Texinfo files are in %BUILDDIR%/texinfo.
goto end
)
if "%1" == "gettext" (
%SPHINXBUILD% -b gettext %I18NSPHINXOPTS% %BUILDDIR%/locale
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The message catalogs are in %BUILDDIR%/locale.
goto end
)
if "%1" == "changes" (
%SPHINXBUILD% -b changes %ALLSPHINXOPTS% %BUILDDIR%/changes
if errorlevel 1 exit /b 1
echo.
echo.The overview file is in %BUILDDIR%/changes.
goto end
)
if "%1" == "linkcheck" (
%SPHINXBUILD% -b linkcheck %ALLSPHINXOPTS% %BUILDDIR%/linkcheck
if errorlevel 1 exit /b 1
echo.
echo.Link check complete; look for any errors in the above output ^
or in %BUILDDIR%/linkcheck/output.txt.
goto end
)
if "%1" == "doctest" (
%SPHINXBUILD% -b doctest %ALLSPHINXOPTS% %BUILDDIR%/doctest
if errorlevel 1 exit /b 1
echo.
echo.Testing of doctests in the sources finished, look at the ^
results in %BUILDDIR%/doctest/output.txt.
goto end
)
if "%1" == "xml" (
%SPHINXBUILD% -b xml %ALLSPHINXOPTS% %BUILDDIR%/xml
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The XML files are in %BUILDDIR%/xml.
goto end
)
if "%1" == "pseudoxml" (
%SPHINXBUILD% -b pseudoxml %ALLSPHINXOPTS% %BUILDDIR%/pseudoxml
if errorlevel 1 exit /b 1
echo.
echo.Build finished. The pseudo-XML files are in %BUILDDIR%/pseudoxml.
goto end
)
:end

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channels/docs/message-standards.rst → docs/message-standards.rst
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docs/scaling.rst Normal file
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Scaling
=======
Of course, one of the downsides of introducing a channel layer to Django it
that it's something else that must scale. Scaling traditional Django as a
WSGI application is easy - you just add more servers and a loadbalancer. Your
database is likely to be the thing that stopped scaling before, and there's
a relatively large amount of knowledge about tackling that problem.
By comparison, there's not as much knowledge about scaling something like this
(though as it is very similar to a task queue, we have some work to build from).
In particular, the fact that messages are at-most-once - we do not guarantee
delivery, in the same way a webserver doesn't guarantee a response - means
we can loosen a lot of restrictions that slow down more traditional task queues.
In addition, because channels can only have single consumers and they're handled
by a fleet of workers all running the same code, we could easily split out
incoming work by sharding into separate clusters of channel backends
and worker servers - any cluster can handle any request, so we can just
loadbalance over them.
Of course, that doesn't work for interface servers, where only a single
particular server is listening to each response channel - if we broke things
into clusters, it might end up that a response is sent on a different cluster
to the one that the interface server is listening on.
That's why Channels labels any *response channel* with a leading ``!``, letting
you know that only one server is listening for it, and thus letting you scale
and shard the two different types of channels accordingly (for more on
the difference, see :ref:`channel-types`).