redis/redis-py · error · RedisClusterException

Cluster Node has no redis_connection

Error message

Cluster Node {target_node.name} has no redis_connection

What it means

Raised as a RedisClusterException by the monitor() method when the target ClusterNode's redis_connection attribute is None, meaning no live Redis connection object has been created for that node. The monitor() method needs a raw connection to stream MONITOR output, so a missing connection is a hard failure.

Solutions

1. Call client.get_redis_connection(target_node) first to force lazy connection creation before calling monitor().
2. If no target_node is passed, let the client pick the default node (pass target_node=None).
3. Verify the node is still part of the cluster topology with client.get_node(host, port) before using it.

Example fix

// before
m = client.monitor(target_node=some_node)

// after
client.get_redis_connection(some_node)
m = client.monitor(target_node=some_node)

# Force connection before calling monitor()
if target_node and target_node.redis_connection is None:
    client.get_redis_connection(target_node)

def node_has_connection(node) -> bool:
    return node.redis_connection is not None

from redis.exceptions import RedisClusterException
try:
    m = client.monitor(target_node=node)
except RedisClusterException as e:
    if 'has no redis_connection' in str(e):
        client.get_redis_connection(node)
        m = client.monitor(target_node=node)

When it happens

Trigger: Calling client.monitor(target_node=some_node) where some_node is a ClusterNode whose redis_connection was never initialized (e.g., a node discovered during topology mapping but never connected to). The check is at cluster.py:1184-1187.

Common situations: Passing a node obtained from get_nodes() or a slot-cache lookup whose lazy connection was never opened, or a node that has been removed from the cluster but still referenced by the application.

Related errors

• Failed to subscribe to cluster nodes
• Invalid Database
• READONLY command failed
• READONLY command failed
• Redis Cluster cannot be connected. Please provide at least…

AI-assisted analysis of redis/redis-py@6a6b581b48 (2026-08-10). Data as JSON: /api/errors/ce0bf8684592e3e5. Report an issue: GitHub.

Appendix: source

Thrown at redis/cluster.py:1185

        self.nodes_manager.default_node = node
        return True

    def set_retry(self, retry: Retry) -> None:
        self.retry = retry

    def monitor(self, target_node=None):
        """
        Returns a Monitor object for the specified target node.
        The default cluster node will be selected if no target node was
        specified.
        Monitor is useful for handling the MONITOR command to the redis server.
        next_command() method returns one command from monitor
        listen() method yields commands from monitor.
        """
        if target_node is None:
            target_node = self.get_default_node()
        if target_node.redis_connection is None:
            raise RedisClusterException(
                f"Cluster Node {target_node.name} has no redis_connection"
            )
        return target_node.redis_connection.monitor()

    def pubsub(self, node=None, host=None, port=None, **kwargs):
        """
        Allows passing a ClusterNode, or host&port, to get a pubsub instance
        connected to the specified node
        """
        return ClusterPubSub(self, node=node, host=host, port=port, **kwargs)

    def keyspace_notifications(
        self,
        key_prefix: Union[str, bytes, None] = None,
        ignore_subscribe_messages: bool = True,
    ) -> "ClusterKeyspaceNotifications":
        """
        Return a :class:`~redis.keyspace_notifications.ClusterKeyspaceNotifications`

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