Fix garbage collection deadlock (#1578)

Author: emorozov

dev_requirements.txt

@@ -1,5 +1,6 @@
 flake8>=3.9.2
 pytest==6.2.5
+pytest-timeout==2.0.1
 tox==3.24.4
 tox-docker==3.1.0
 invoke==1.6.0

redis/connection.py

@@ -10,6 +10,7 @@
 import socket
 import threading
 import warnings
+import weakref
 
 from redis.exceptions import (
     AuthenticationError,
@@ -562,7 +563,7 @@ def __del__(self):
             pass
 
     def register_connect_callback(self, callback):
-        self._connect_callbacks.append(callback)
+        self._connect_callbacks.append(weakref.WeakMethod(callback))
 
     def clear_connect_callbacks(self):
         self._connect_callbacks = []
@@ -588,8 +589,10 @@ def connect(self):
 
         # run any user callbacks. right now the only internal callback
         # is for pubsub channel/pattern resubscription
-        for callback in self._connect_callbacks:
-            callback(self)
+        for ref in self._connect_callbacks:
+            callback = ref()
+            if callback:
+                callback(self)
 
     def _connect(self):
         "Create a TCP socket connection"

tests/test_pubsub.py

@@ -570,3 +570,15 @@ def exception_handler(ex, pubsub, thread):
         assert event.wait(timeout=1.0)
         pubsub_thread.join(timeout=1.0)
         assert not pubsub_thread.is_alive()
+
+
+class TestPubSubDeadlock:
+    @pytest.mark.timeout(30, method='thread')
+    def test_pubsub_deadlock(self, master_host):
+        pool = redis.ConnectionPool(host=master_host)
+        r = redis.Redis(connection_pool=pool)
+
+        for i in range(60):
+            p = r.pubsub()
+            p.subscribe("my-channel-1", "my-channel-2")
+            pool.reset()