redis-py: timeout connecting to redis hosted on aws ElastiCache

Hi,

I have a redis server hosted by aws using aws ElastiCache. When I try to connect to it using a lambda and on my local machine, it gives ‘timeout connecting to server’ error. However, my colleague could connect to this redis using another client in PHP. I wonder what I did wrong.

try:
        redisClient = redis.Redis(host='***.use1.cache.amazonaws.com', port=6379, db=0, socket_timeout=10)
        print(redisClient)
        try:
            print(redisClient.ping())
            print(redisClient.set('foo','bar'))
            # r.get('foo')
        except Exception as e:
            print('get set error: ', e)
    except Exception as e:
        print('redis err: ', e)

// redisClient Redis<ConnectionPool<Connection<host=***.use1.cache.amazonaws.com,port=6379,db=0>>>

// get set error:  Timeout connecting to server for ping or set

Without setting the socket_timeout parameter, it will time out based on redis-py operation timeout: Error 60 connecting to ***.use1.cache.amazonaws.com:6379. Operation timed out.

About this issue

Original URL
State: open
Created 6 years ago
Comments: 17 (3 by maintainers)

Most upvoted comments

I ran into this issue as well, but from a Lambda. For me, there were a few problems that had to be ironed out

The lambda needs VPC permissions.
The ElastiCache security group needs an inbound rule from the Lambda security group that allows communication on the Redis port. I thought they could just be in the same security group.
And the real kicker: I had turned on encryption in-transit. This meant that I needed to pass redis.RedisClietn(... ssl=True). The redis-py page mentions that ssl_cert_reqs needs to be set to None for use with ElastiCache, but that didn’t seem to be true in my case. I did however need to pass ssl=True.

It makes sense that ssl=True needed to be set but the connection was just timing out so I went round and round trying to figure out what the problem with the permissions/VPC/SG setup was.

+32

john-feusi-neuro on Jun 27, 2019

When I try to connect to it using a lambda and on my local machine

You can only connect to elasticache via a machine running in the same region. It’s in the docs somewhere.

+14

211217613 on Jul 21, 2018

This is happening randomly. Is there are way to tell redis-py to reconnect on connection timeouts with some backoff strategy?

dejlek on Oct 10, 2018

@chayim , do you by any chance know how to make Celery use retry_on_timeout setting by any chance?

dejlek on Feb 18, 2022

Yes you need to be in the same region. Also test with the redis-cli too, to rule out firewall rules, routing etc.

grumps on Aug 5, 2018