Fix bug: client side caching causes unexpected disconnections (#3160)

* fix disconnects

* skip test in cluster

---------

Co-authored-by: Chayim <chayim@users.noreply.github.com>

Author: dvora-h

redis/_parsers/resp3.py

@@ -117,7 +117,9 @@ def _read_response(self, disable_decoding=False, push_request=False):
                 )
                 for _ in range(int(response))
             ]
-            self.handle_push_response(response, disable_decoding, push_request)
+            response = self.handle_push_response(
+                response, disable_decoding, push_request
+            )
         else:
             raise InvalidResponse(f"Protocol Error: {raw!r}")
 

redis/client.py

@@ -563,10 +563,10 @@ def execute_command(self, *args, **options):
         pool = self.connection_pool
         conn = self.connection or pool.get_connection(command_name, **options)
         response_from_cache = conn._get_from_local_cache(args)
-        if response_from_cache is not None:
-            return response_from_cache
-        else:
-            try:
+        try:
+            if response_from_cache is not None:
+                return response_from_cache
+            else:
                 response = conn.retry.call_with_retry(
                     lambda: self._send_command_parse_response(
                         conn, command_name, *args, **options
@@ -575,9 +575,9 @@ def execute_command(self, *args, **options):
                 )
                 conn._add_to_local_cache(args, response, keys)
                 return response
-            finally:
-                if not self.connection:
-                    pool.release(conn)
+        finally:
+            if not self.connection:
+                pool.release(conn)
 
     def parse_response(self, connection, command_name, **options):
         """Parses a response from the Redis server"""

redis/commands/core.py

@@ -2011,7 +2011,7 @@ def mget(self, keys: KeysT, *args: EncodableT) -> ResponseT:
         options = {}
         if not args:
             options[EMPTY_RESPONSE] = []
-        options["keys"] = keys
+        options["keys"] = args
         return self.execute_command("MGET", *args, **options)
 
     def mset(self, mapping: Mapping[AnyKeyT, EncodableT]) -> ResponseT:

redis/connection.py

@@ -1,6 +1,5 @@
 import copy
 import os
-import select
 import socket
 import ssl
 import sys
@@ -609,11 +608,6 @@ def pack_commands(self, commands):
             output.append(SYM_EMPTY.join(pieces))
         return output
 
-    def _socket_is_empty(self):
-        """Check if the socket is empty"""
-        r, _, _ = select.select([self._sock], [], [], 0)
-        return not bool(r)
-
     def _cache_invalidation_process(
         self, data: List[Union[str, Optional[List[str]]]]
     ) -> None:
@@ -639,7 +633,7 @@ def _get_from_local_cache(self, command: str):
             or command[0] not in self.cache_whitelist
         ):
             return None
-        while not self._socket_is_empty():
+        while self.can_read():
             self.read_response(push_request=True)
         return self.client_cache.get(command)
 
@@ -1187,12 +1181,15 @@ def get_connection(self, command_name: str, *keys, **options) -> "Connection":
         try:
             # ensure this connection is connected to Redis
             connection.connect()
-            # connections that the pool provides should be ready to send
-            # a command. if not, the connection was either returned to the
+            # if client caching is not enabled connections that the pool
+            # provides should be ready to send a command.
+            # if not, the connection was either returned to the
             # pool before all data has been read or the socket has been
             # closed. either way, reconnect and verify everything is good.
+            # (if caching enabled the connection will not always be ready
+            # to send a command because it may contain invalidation messages)
             try:
-                if connection.can_read():
+                if connection.can_read() and connection.client_cache is None:
                     raise ConnectionError("Connection has data")
             except (ConnectionError, OSError):
                 connection.disconnect()

tests/test_cache.py

@@ -146,6 +146,49 @@ def test_cache_return_copy(self, r):
         check = cache.get(("LRANGE", "mylist", 0, -1))
         assert check == [b"baz", b"bar", b"foo"]
 
+    @pytest.mark.onlynoncluster
+    @pytest.mark.parametrize(
+        "r",
+        [{"cache": _LocalCache(), "kwargs": {"decode_responses": True}}],
+        indirect=True,
+    )
+    def test_csc_not_cause_disconnects(self, r):
+        r, cache = r
+        id1 = r.client_id()
+        r.mset({"a": 1, "b": 1, "c": 1, "d": 1, "e": 1, "f": 1})
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["1", "1", "1", "1", "1", "1"]
+        id2 = r.client_id()
+
+        # client should get value from client cache
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["1", "1", "1", "1", "1", "1"]
+        assert cache.get(("MGET", "a", "b", "c", "d", "e", "f")) == [
+            "1",
+            "1",
+            "1",
+            "1",
+            "1",
+            "1",
+        ]
+
+        r.mset({"a": 2, "b": 2, "c": 2, "d": 2, "e": 2, "f": 2})
+        id3 = r.client_id()
+        # client should get value from redis server post invalidate messages
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["2", "2", "2", "2", "2", "2"]
+
+        r.mset({"a": 3, "b": 3, "c": 3, "d": 3, "e": 3, "f": 3})
+        # need to check that we get correct value 3 and not 2
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["3", "3", "3", "3", "3", "3"]
+        # client should get value from client cache
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["3", "3", "3", "3", "3", "3"]
+
+        r.mset({"a": 4, "b": 4, "c": 4, "d": 4, "e": 4, "f": 4})
+        # need to check that we get correct value 4 and not 3
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["4", "4", "4", "4", "4", "4"]
+        # client should get value from client cache
+        assert r.mget("a", "b", "c", "d", "e", "f") == ["4", "4", "4", "4", "4", "4"]
+        id4 = r.client_id()
+        assert id1 == id2 == id3 == id4
+
 
 @pytest.mark.skipif(HIREDIS_AVAILABLE, reason="PythonParser only")
 @pytest.mark.onlycluster