Fix initialization order in KafkaClient (dpkp#2119)

Fix initialization order in KafkaClient

Author: pecalleja

kafka/client_async.py

@@ -200,18 +200,22 @@ def __init__(self, **configs):
             if key in configs:
                 self.config[key] = configs[key]
 
+        # these properties need to be set on top of the initialization pipeline
+        # because they are used when __del__ method is called
+        self._closed = False
+        self._wake_r, self._wake_w = socket.socketpair()
+        self._selector = self.config['selector']()
+
         self.cluster = ClusterMetadata(**self.config)
         self._topics = set()  # empty set will fetch all topic metadata
         self._metadata_refresh_in_progress = False
-        self._selector = self.config['selector']()
         self._conns = Dict()  # object to support weakrefs
         self._api_versions = None
         self._connecting = set()
         self._sending = set()
         self._refresh_on_disconnects = True
         self._last_bootstrap = 0
         self._bootstrap_fails = 0
-        self._wake_r, self._wake_w = socket.socketpair()
         self._wake_r.setblocking(False)
         self._wake_w.settimeout(self.config['wakeup_timeout_ms'] / 1000.0)
         self._wake_lock = threading.Lock()
@@ -225,7 +229,6 @@ def __init__(self, **configs):
 
         self._selector.register(self._wake_r, selectors.EVENT_READ)
         self._idle_expiry_manager = IdleConnectionManager(self.config['connections_max_idle_ms'])
-        self._closed = False
         self._sensors = None
         if self.config['metrics']:
             self._sensors = KafkaClientMetrics(self.config['metrics'],