Redis Pub/Sub with Python (notes for my collegue)

README.md

Redis Pub/Sub with Python

Overview:

• Redis supports PUB/SUB
• It supports pattern matching. Clients may subscribe to glob-style patterns in order to receive all the messages sent to channel names matching a given pattern.

Prerequisites

Assuming Fedora 23.

dnf install redis
systemctl start redis
systemctl enable redis

dnf install python
pip install redis

Test setup

One terminal with:

./listener.py

Another with

redis-cli # opens a repl, all subsequent commands should show something in the first terminal
> publish hausmeister "new_user_created 123456" # I made up the convention of the message (action)
> publish worker.control "new_job 123456"
> publish worker.registration "done 123456" # yes we can use nested queues
> publish nirvana "nobody listens" # the listener is not subscribed, hence, we should not see anything
> publish worker.control KILL # terminate `listener.py`

listener.py

#!/usr/bin/env python

# inspired by: https://gist.github.com/jobliz/2596594

import redis
import threading

class Listener(threading.Thread):
    def __init__(self, r):
        threading.Thread.__init__(self)
        self.redis = r
        self.pubsub = self.redis.pubsub()
        self.pubsub.subscribe(['hausmeister'])
        self.pubsub.psubscribe(['worker.*'])

    def work(self, item):
        print item['channel'], ":", item['data']

    def run(self):
        for item in self.pubsub.listen():
            if item['data'] == "KILL":
                self.pubsub.unsubscribe()
                print self, "unsubscribed and finished"
                break
            else:
                self.work(item)

if __name__ == '__main__':
    r = redis.Redis('127.0.0.1')
    client = Listener(r)
    client.start()

When in Python3, it's better to add decode_responses=True when start redis.

r = redis.Redis('127.0.0.1', decode_responses=True)

@daimajia
but why?