text: import asyncio
  import logging
  import random
  from collections import defaultdict
  from functools import partial
  
  from retrial.retrial import retry
  
  from .packet import ControlPacket
  from .protocol_factory import get_vyked_protocol
  from .pinger import TCPPinger
  
  
  def _retry_for_result(result):
      if isinstance(result, tuple):
          return not isinstance(result[0], asyncio.transports.Transport) or not isinstance(result[1], asyncio.Protocol)
      return True
  
  
  def _retry_for_exception(_):
      return True
  
  
  class RegistryClient:
      def __init__(self, loop, host, port, ssl_context=None):
          self._loop = loop
          self._port = port
          self._host = host
          self.bus = None
          self._transport = None
          self._protocol = None
          self._service = None
          self._version = None
          self._node_ids = {}
          self._pinger = None
          self._conn_handler = None
          self._pending_requests = {}
          self._available_services = defaultdict(list)
          self._assigned_services = defaultdict(lambda: defaultdict(list))
          self._ssl_context = ssl_context
          self.logger = logging.getLogger(__name__)
  
      @property
      def conn_handler(self):
          return self._conn_handler
  
      @conn_handler.setter
      def conn_handler(self, handler):
          self._conn_handler = handler
  
      def register(self, ip, port, service, version, node_id, vendors, service_type):
          self._service = service
          self._version = version
          self._node_ids[service_type] = node_id
          packet = ControlPacket.registration(ip, port, node_id, service, version, vendors, service_type)
          self._protocol.send(packet)
  
      def get_instances(self, name, version):
          packet = ControlPacket.get_instances(name, version)
          future = asyncio.Future()
          self._protocol.send(packet)
          self._pending_requests[packet['request_id']] = future
          return future
  
      def get_subscribers(self, service, version, endpoint):
          packet = ControlPacket.get_subscribers(service, version, endpoint)
          # TODO : remove duplication in get_instances and get_subscribers
          future = asyncio.Future()
          self._protocol.send(packet)
          self._pending_requests[packet['request_id']] = future
          return future
  
      def x_subscribe(self, host, port, node_id, endpoints):
          packet = ControlPacket.xsubscribe(self._service, self._version, host, port, node_id,
                                            endpoints)
          self._protocol.send(packet)
  
      @retry(should_retry_for_result=_retry_for_result, should_retry_for_exception=_retry_for_exception,
             strategy=[0, 2, 4, 8, 16, 32])
      def connect(self):
          self._transport, self._protocol = yield from self._loop.create_connection(partial(get_vyked_protocol, self),
                                                                                    self._host, self._port,
                                                                                    ssl=self._ssl_context)
          yield from self.conn_handler.handle_connected()
          self._pinger = TCPPinger(self._host, self._port, 'registry', self._protocol, self)
          self._pinger.ping(payload=self._node_ids)
          return self._transport, self._protocol
  
      def on_timeout(self, host, port, node_id):
          asyncio.async(self.connect())
  
      def receive(self, packet: dict, protocol, transport):
          if packet['type'] == 'registered':
              self.cache_vendors(packet['params']['dependencies'])
              self.bus.registration_complete()
          elif packet['type'] == 'new_instance':
              # TODO : once method for both vendors and new instance
              self.cache_instance(**packet['params'])
              self._handle_new_instance(**packet['params'])
          elif packet['type'] == 'deregister':
              self._handle_deregistration(packet)
          elif packet['type'] == 'subscribers':
              self._handle_subscriber_packet(packet)
          elif packet['type'] == 'pong':
              self._pinger.pong_received(payload=self._node_ids)
          elif packet['type'] == 'instances':
              self._handle_get_instances(packet)
  
      def get_all_addresses(self, name, version):
          return self._available_services.get(
              self._get_full_service_name(name, version))
  
      def get_for_node(self, node_id):
          for services in self._available_services.values():
              for host, port, node, service_type in services:
                  if node == node_id:
                      return host, port, node, service_type
          return None
  
      def get_random_service(self, service_name, service_type):
          services = self._available_services[service_name]
          services = [service for service in services if service[3] == service_type]
          if len(services):
              return random.choice(services)
          else:
              return None
  
      def resolve(self, service: str, version: str, entity: str, service_type: str):
          service_name = self._get_full_service_name(service, version)
          if entity is not None:
              entity_map = self._assigned_services.get(service_name)
              if entity_map is None:
                  self._assigned_services[service_name] = {}
              entity_map = self._assigned_services.get(service_name)
              if entity in entity_map:
                  return entity_map[entity]
              else:
                  host, port, node_id, service_type = self.get_random_service(service_name, service_type)
                  if node_id is not None:
                      entity_map[entity] = host, port, node_id, service_type
                  return host, port, node_id, service_type
          else:
              return self.get_random_service(service_name, service_type)
  
      @staticmethod
      def _get_full_service_name(service, version):
          return "{}/{}".format(service, version)
  
      def cache_vendors(self, dependencies):
          for dependency in dependencies:
              vendor_name = self._get_full_service_name(dependency['name'], dependency['version'])
              for address in dependency['addresses']:
                  self._available_services[vendor_name].append(
                      (address['host'], address['port'], address['node_id'], address['type']))
          self.logger.debug('Connection cache after registration is %s', self._available_services)
  
      def cache_instance(self, name, version, host, port, node_id, service_type):
          vendor = self._get_full_service_name(name, version)
          self._available_services[vendor].append((host, port, node_id, service_type))
          self.logger.debug('Connection cache on getting new instance is %s', self._available_services)
  
      def _handle_deregistration(self, packet):
          params = packet['params']
          vendor = self._get_full_service_name(params['name'], params['version'])
          node = params['node_id']
          for each in self._available_services[vendor]:
              if each[2] == node:
                  self._available_services[vendor].remove(each)
          entity_map = self._assigned_services.get(vendor)
          if entity_map is not None:
              stale_entities = []
              for entity, node_id in entity_map.items():
                  if node == node_id:
                      stale_entities.append(entity)
              for entity in stale_entities:
                  entity_map.pop(entity)
          self.logger.debug('Connection cache after deregister is %s', self._available_services)
  
      def _handle_subscriber_packet(self, packet):
          request_id = packet['request_id']
          future = self._pending_requests.pop(request_id, None)
          future.set_result(packet['params']['subscribers'])
  
      def _handle_get_instances(self, packet):
          future = self._pending_requests.pop(packet['request_id'], None)
          future.set_result(packet['params']['instances'])
  
      def _handle_new_instance(self, name, version, host, port, node_id, service_type):
          self.bus.new_instance(name, version, host, port, node_id, service_type)
  