redis/redis-py · error · ConnectionError

READONLY command failed

Error message

READONLY command failed

What it means

Error "READONLY command failed" thrown in redis/redis-py.

Source

Thrown at redis/cluster.py:1026

                    # Client was already disconnected. do nothing
                    pass

    def on_connect(self, connection):
        """
        Initialize the connection, authenticate and select a database and send
         READONLY if it is set during object initialization.
        """
        connection.on_connect()

        if self.read_from_replicas or self.load_balancing_strategy:
            # Sending READONLY command to server to configure connection as
            # readonly. Since each cluster node may change its server type due
            # to a failover, we should establish a READONLY connection
            # regardless of the server type. If this is a primary connection,
            # READONLY would not affect executing write commands.
            connection.send_command("READONLY")
            if str_if_bytes(connection.read_response()) != "OK":
                raise ConnectionError("READONLY command failed")

        if self.user_on_connect_func is not None:
            self.user_on_connect_func(connection)

    def get_redis_connection(self, node: "ClusterNode") -> Redis:
        if not node.redis_connection:
            with self._lock:
                if not node.redis_connection:
                    self.nodes_manager.create_redis_connections([node])
        return node.redis_connection

    def get_node(self, host=None, port=None, node_name=None):
        return self.nodes_manager.get_node(host, port, node_name)

    def get_primaries(self):
        return self.nodes_manager.get_nodes_by_server_type(PRIMARY)

    def get_replicas(self):

View on GitHub (pinned to da03cdc7e8)

When it happens

Trigger: Thrown at redis/cluster.py:1026 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of redis/redis-py@da03cdc7e8 (2026-08-04). Data as JSON: /data/errors/313e23c2a41db5bc.json. Report an issue: GitHub.