How to connect to AWS elasticache cluster nodes through a bastion using Python and redis-py-cluster?

I've been hitting my head against a wall all day today with this. I'm tunneling into a EC2 instance Bastion server that has access to my Elasticache cluster. I am able to create the connection in my code to the cluster that I've tunneled to, but when I execute anything against the cluster, I get a "ClusterError: TTL exhausted".

I think the problem is that the nodes in the connection pool are still the DNS that AWS provides, so when it tries to connect to those, it gets a connection refused (at least that is what it seems like). I've tried to use the host_port_remap property but it doesn't support any host that isn't an IP address, so I can't map the AWS DNS to localhost. Any ideas how I can connect and execute against the cluster using this method?

redis_cluster = RedisCluster(
                        host='localhost',
                        port=6379,
                        ssl=True,
                        ssl_cert_reqs=None,
                        decode_responses=True,
                        skip_full_coverage_check=True,
                        password=password)
redis_cluster.set("foo", "bar")`

I've tried to use the host_port_remap to map the AWS DNS to my localhost. I've tried creating a local Redis cluster in a docker container and connect to that through the AWS SAM lambda running locally, but that also seems to have connection issues.

Solution

For anyone who runs into the same issue, did kind of a hacky workaround.

def _map_local_cluster(redis_cluster):
    # need to map the redis cluster nodes to the docker localhost so it can point back to tunneled connection
    # also need to set the remap rule applies function because it expects the host to be an IP but the RedisCluster
    # creates the nodes with the AWS DNS
    host_port_remap = [
        {
            'from_host': '<one nodes DNS on AWS>',
            'from_port': 6379,
            'to_host': 'host.docker.internal',
            'to_port': 6380,
        },
        {
            'from_host': '<other nodes DNS on AWS>',
            'from_port': 6379,
            'to_host': 'host.docker.internal',
            'to_port': 6381,
        },
    ]

    def _remap_rule_applies(remap_rule, node_obj):
        return node_obj[0] == remap_rule['from_host']

    redis_cluster.connection_pool.nodes.host_port_remap = host_port_remap
    redis_cluster.connection_pool.nodes._remap_rule_applies = _remap_rule_applies