Start a redis server in the background on a free tcp port

redis_server.py

import subprocess
import random
import os


class RedisServer(object):
    def __init__(self, dockerimage=None):
        while True:
            self._proc = None
            self._port = random.randint(1025, 65535)
            if dockerimage:
                cmd = 'docker run --rm -p {port}:6379 {image} --save'.format(port=self.port, image=dockerimage)
            else:
                cmd = 'redis-server --save --port {port}'.format(port=self.port)
            self._proc = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
            seen_redis = False
            while True:
                line = self._proc.stdout.readline()
                if b'Redis' in line:
                    seen_redis = True
                if line == b'':
                    self._port = None
                    break
                elif b'Ready to accept connections' in line:
                    break
                elif b'Opening Unix socket' in line and b'Address already in use' in line:
                    raise Exception('Unix domain already in use')
            # usually could not find docker image
            if not seen_redis:
                raise Exception('Could not run redis')
            if self._port:
                break

    @property
    def port(self):
        return self._port

    def __del__(self):
        if self._proc:
            try:
                self._proc.kill()
            except Exception:
                pass
            self._proc = None


if __name__ == "__main__":
    from redis import Redis

    rs = RedisServer(dockerimage='redis:4.0')
    r = Redis(port=rs.port)
    print(r.set('a', 'a'))
    print(r.get('a'))