redis-websocket-api

An extensible Redis-over-WebSocket API on top of websockets and aioredis.

Installation

For basic functionality:

pip install redis_websocket_api

With geo extension (filtering messages by extent, projection transformation):

pip install redis_websocket_api[geo]

Server-Side Usage

For a quick test you can run

python -m redis_websocket_api

to start a simple redis websocket api on ws://localhost:8765.

This does roughly the equivalant of:

from aioredis import from_url
from redis_websocket_api import WebsocketServer, WebsocketHandler


class PublishEverythingHandler(WebsocketHandler):

    def channel_is_allowed(self, channel_name):
        return True


WebsocketServer(
    redis=from_url("redis:///", encoding="utf-8", decode_responses=True),
    read_timeout=30,
    keep_alive_timeout=120,
    handler_class=PublishEverythingHandler,
).listen(
    host='localhost',
    port=8000,
    channel_patterns=["[a-z]*"],
)

Have a look at examples/demo.py for an example with the GeoCommandsMixin added.

Client-Side Usage

WebsocketHandler

The default functionality provides the following interface to the web client (expecting the requests over a websocket connection):

• GET key translates to hvals key
• GET key hkey translates to hget key hkey
• SUB key subscribes the websocket to a redis channel (using a single redis connection pool for all clients)
• DEL key unsubscribes the client from the channel
• PING causes a PONG response (to avoid timeouts)

Subclass of WebsocketHandler with GeoCommandsMixin added

By adding the GeoCommandsMixin the web client can use

• BBOX left bottom right top to only receive GeoJSON features within this box plus all messages which are not valid GeoJSON
• PROJECTION epsg:number causes all future GeoJSON features to be transformed to the given projection

See examples/demo.py for how to use an extended WebsocketHandler subclass.

Geo commands are currently limited to LineString, Polygon, and Point geometries.

Note that the projection input and output coordinates will use the traditional GIS order, that is longitude, latitude for geographic CRS and easting, northing for most projected CRS. If you want the input and output axis order to strictly follow the definition of the CRS, use StrictAxisOrderGeoCommandsMixin instead of GeoCommandsMixin.

Build your own protocol

Using the commands listed above for communicating from client to server is completly optional and determinded by the Mixin classes added to the WebsocketHandlerBase.