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Posix IPC-backed ASGI channel layer implementation

Project description

An ASGI channel layer that uses POSIX shared memory IPC as its backing store (only works between processes on the same machine).

IPC is still a bit of a wild west of UNIX compatability, so if you find weird errors, please file an issue with details and exact system specifications. In partcular, this module is tested and works well on Linux kernels and the Windows Subsystem for Linux; it also works on Mac OS but will not be able to detect deadlock situations due to limitations in the kernel.


You’ll need to instantiate the channel layer with a path prefix to create IPC objects underneath; any channel layers with the same prefix will talk to each other as long as they’re on the same machine.


import asgi_ipc as asgi

channel_layer = asgi.IPCChannelLayer(
    message_memory=200 * 1024 * 1024,

channel_layer.send("my_channel", {"text": "Hello ASGI"})
print(channel_layer.receive(["my_channel", ]))


Prefix to use for IPC objects under the root namespace. Defaults to asgi. IPC layers on the same machine with the same prefix will talk to each other.


The amount of shared memory to allocate to the channel storage, in bytes. Defaults to 100MB. All of your in-flight messages must fit into this, otherwise you’ll get ChannelFull errors if the memory space is full up.

ASGI messages can be a maximum of one megabyte, and are usually much smaller. The IPC routing metadata on top of each message is approximately 50 bytes.


The amount of shared memory to allocate to the group storage, in bytes. Defaults to 20MB. All of your group membership data must fit into this space, otherwise your group memberships may fail to persist.

You can fit approximately 4000 group-channel membership associations into one megabyte of memory.


Message expiry in seconds. Defaults to 60. You generally shouldn’t need to change this, but you may want to turn it down if you have peaky traffic you wish to drop, or up if you have peaky traffic you want to backlog until you get to it.


Group expiry in seconds. Defaults to 86400. Interface servers will drop connections after this amount of time; it’s recommended you reduce it for a healthier system that encourages disconnections.


Default channel capacity. Defaults to 100. Once a channel is at capacity, it will refuse more messages. How this affects different parts of the system varies; a HTTP server will refuse connections, for example, while Django sending a response will just wait until there’s space.


Per-channel capacity configuration. This lets you tweak the channel capacity based on the channel name, and supports both globbing and regular expressions.

It should be a dict mapping channel name pattern to desired capacity; if the dict key is a string, it’s intepreted as a glob, while if it’s a compiled re object, it’s treated as a regular expression.

This example sets http.request to 200, all http.response! channels to 10, and all websocket.send! channels to 20:

    "http.request": 200,
    "http.response!*": 10,
    re.compile(r"^websocket.send\!.+"): 20,

If you want to enforce a matching order, use an OrderedDict as the argument; channels will then be matched in the order the dict provides them.


All Channels projects currently support Python 2.7, 3.4 and 3.5.


Please refer to the main Channels contributing docs. That also contains advice on how to set up the development environment and run the tests.

Maintenance and Security

To report security issues, please contact For GPG signatures and more security process information, see

To report bugs or request new features, please open a new GitHub issue.

This repository is part of the Channels project. For the shepherd and maintenance team, please see the main Channels readme.

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