only send readonly to replicas once on new connections

rediscluster/client.py

@@ -578,7 +578,6 @@ def _execute_command(self, *args, **kwargs):
 
         redirect_addr = None
         asking = False
-        is_read_replica = False
 
         try_random_node = False
         slot = self._determine_slot(*args)
@@ -605,7 +604,6 @@ def _execute_command(self, *args, **kwargs):
                             slot,
                             self.read_from_replicas and (command in self.READ_COMMANDS)
                         )
-                        is_read_replica = node['server_type'] == 'slave'
 
                     connection = self.connection_pool.get_connection_by_node(node)
 
@@ -615,12 +613,6 @@ def _execute_command(self, *args, **kwargs):
                     connection.send_command('ASKING')
                     self.parse_response(connection, "ASKING", **kwargs)
                     asking = False
-                if is_read_replica:
-                    # Ask read replica to accept reads (see https://redis.io/commands/readonly)
-                    # TODO: do we need to handle errors from this response?
-                    connection.send_command('READONLY')
-                    self.parse_response(connection, 'READONLY', **kwargs)
-                    is_read_replica = False
 
                 connection.send_command(*args)
                 return self.parse_response(connection, command, **kwargs)

rediscluster/connection.py

@@ -343,6 +343,10 @@ def get_connection_by_node(self, node):
             connection = self._available_connections.get(node["name"], []).pop()
         except IndexError:
             connection = self.make_connection(node)
+            if node["server_type"] == "slave":
+                connection.send_command('READONLY')
+                if nativestr(connection.read_response()) != 'OK':
+                    raise ConnectionError('READONLY command failed')
 
         self._in_use_connections.setdefault(node["name"], set()).add(connection)