Optionally disable disconnects in read_response (redis#2695) (#24)

* Add regression tests and fixes for issue redis#1128

* Fix tests for resumable read_response to use "disconnect_on_error"

* undo prevision fix attempts in async client and cluster

* re-enable cluster test

* Suggestions from code review

* Add CHANGES

Co-authored-by: Kristján Valur Jónsson <[email protected]>

Author: dlunch

CHANGES

@@ -1,3 +1,4 @@
+    * Revert #2104, #2673, add `disconnect_on_error` option to `read_response()` (issues #2506, #2624)
     * Fix string cleanse in Redis Graph
     * Make PythonParser resumable in case of error (#2510)
     * Add `timeout=None` in `SentinelConnectionManager.read_response`

redis/asyncio/client.py

@@ -516,9 +516,20 @@ async def execute_command(self, *args, **options):
         command_name = args[0]
         conn = self.connection or await pool.get_connection(command_name, **options)
 
-        return await asyncio.shield(
-            self._try_send_command_parse_response(conn, *args, **options)
-        )
+        if self.single_connection_client:
+            await self._single_conn_lock.acquire()
+        try:
+            return await conn.retry.call_with_retry(
+                lambda: self._send_command_parse_response(
+                    conn, command_name, *args, **options
+                ),
+                lambda error: self._disconnect_raise(conn, error),
+            )
+        finally:
+            if self.single_connection_client:
+                self._single_conn_lock.release()
+            if not self.connection:
+                await pool.release(conn)
 
     async def parse_response(
         self, connection: Connection, command_name: Union[str, bytes], **options
@@ -757,18 +768,10 @@ async def _disconnect_raise_connect(self, conn, error):
         is not a TimeoutError. Otherwise, try to reconnect
         """
         await conn.disconnect()
-
         if not (conn.retry_on_timeout and isinstance(error, TimeoutError)):
             raise error
         await conn.connect()
 
-    async def _try_execute(self, conn, command, *arg, **kwargs):
-        try:
-            return await command(*arg, **kwargs)
-        except asyncio.CancelledError:
-            await conn.disconnect()
-            raise
-
     async def _execute(self, conn, command, *args, **kwargs):
         """
         Connect manually upon disconnection. If the Redis server is down,
@@ -777,11 +780,9 @@ async def _execute(self, conn, command, *args, **kwargs):
         called by the # connection to resubscribe us to any channels and
         patterns we were previously listening to
         """
-        return await asyncio.shield(
-            conn.retry.call_with_retry(
-                lambda: self._try_execute(conn, command, *args, **kwargs),
-                lambda error: self._disconnect_raise_connect(conn, error),
-            )
+        return await conn.retry.call_with_retry(
+            lambda: command(*args, **kwargs),
+            lambda error: self._disconnect_raise_connect(conn, error),
         )
 
     async def parse_response(self, block: bool = True, timeout: float = 0):
@@ -799,7 +800,9 @@ async def parse_response(self, block: bool = True, timeout: float = 0):
             await conn.connect()
 
         read_timeout = None if block else timeout
-        response = await self._execute(conn, conn.read_response, timeout=read_timeout)
+        response = await self._execute(
+            conn, conn.read_response, timeout=read_timeout, disconnect_on_error=False
+        )
 
         if conn.health_check_interval and response == self.health_check_response:
             # ignore the health check message as user might not expect it
@@ -1183,18 +1186,6 @@ async def _disconnect_reset_raise(self, conn, error):
             await self.reset()
             raise
 
-    async def _try_send_command_parse_response(self, conn, *args, **options):
-        try:
-            return await conn.retry.call_with_retry(
-                lambda: self._send_command_parse_response(
-                    conn, args[0], *args, **options
-                ),
-                lambda error: self._disconnect_reset_raise(conn, error),
-            )
-        except asyncio.CancelledError:
-            await conn.disconnect()
-            raise
-
     async def immediate_execute_command(self, *args, **options):
         """
         Execute a command immediately, but don't auto-retry on a
@@ -1210,8 +1201,12 @@ async def immediate_execute_command(self, *args, **options):
                 command_name, self.shard_hint
             )
             self.connection = conn
-        return await asyncio.shield(
-            self._try_send_command_parse_response(conn, *args, **options)
+
+        return await conn.retry.call_with_retry(
+            lambda: self._send_command_parse_response(
+                conn, command_name, *args, **options
+            ),
+            lambda error: self._disconnect_reset_raise(conn, error),
         )
 
     def pipeline_execute_command(self, *args, **options):
@@ -1379,19 +1374,6 @@ async def _disconnect_raise_reset(self, conn: Connection, error: Exception):
             await self.reset()
             raise
 
-    async def _try_execute(self, conn, execute, stack, raise_on_error):
-        try:
-            return await conn.retry.call_with_retry(
-                lambda: execute(conn, stack, raise_on_error),
-                lambda error: self._disconnect_raise_reset(conn, error),
-            )
-        except asyncio.CancelledError:
-            # not supposed to be possible, yet here we are
-            await conn.disconnect(nowait=True)
-            raise
-        finally:
-            await self.reset()
-
     async def execute(self, raise_on_error: bool = True):
         """Execute all the commands in the current pipeline"""
         stack = self.command_stack
@@ -1413,11 +1395,10 @@ async def execute(self, raise_on_error: bool = True):
         conn = cast(Connection, conn)
 
         try:
-            return await asyncio.shield(
-                self._try_execute(conn, execute, stack, raise_on_error)
+            return await conn.retry.call_with_retry(
+                lambda: execute(conn, stack, raise_on_error),
+                lambda error: self._disconnect_raise_reset(conn, error),
             )
-        except RuntimeError:
-            await self.reset()
         finally:
             await self.reset()
 

redis/asyncio/cluster.py

@@ -1002,33 +1002,12 @@ async def execute_command(self, *args: Any, **kwargs: Any) -> Any:
         await connection.send_packed_command(connection.pack_command(*args), False)
 
         # Read response
-        return await asyncio.shield(
-            self._parse_and_release(connection, args[0], **kwargs)
-        )
-
-    async def _parse_and_release(self, connection, *args, **kwargs):
         try:
-            return await self.parse_response(connection, *args, **kwargs)
-        except asyncio.CancelledError:
-            # should not be possible
-            await connection.disconnect(nowait=True)
-            raise
+            return await self.parse_response(connection, args[0], **kwargs)
         finally:
+            # Release connection
             self._free.append(connection)
 
-    async def _try_parse_response(self, cmd, connection, ret):
-        try:
-            cmd.result = await asyncio.shield(
-                self.parse_response(connection, cmd.args[0], **cmd.kwargs)
-            )
-        except asyncio.CancelledError:
-            await connection.disconnect(nowait=True)
-            raise
-        except Exception as e:
-            cmd.result = e
-            ret = True
-        return ret
-
     async def execute_pipeline(self, commands: List["PipelineCommand"]) -> bool:
         # Acquire connection
         connection = self.acquire_connection()
@@ -1041,7 +1020,13 @@ async def execute_pipeline(self, commands: List["PipelineCommand"]) -> bool:
         # Read responses
         ret = False
         for cmd in commands:
-            ret = await asyncio.shield(self._try_parse_response(cmd, connection, ret))
+            try:
+                cmd.result = await self.parse_response(
+                    connection, cmd.args[0], **cmd.kwargs
+                )
+            except Exception as e:
+                cmd.result = e
+                ret = True
 
         # Release connection
         self._free.append(connection)

redis/asyncio/connection.py

@@ -796,7 +796,11 @@ async def send_packed_command(
             raise ConnectionError(
                 f"Error {err_no} while writing to socket. {errmsg}."
             ) from e
-        except Exception:
+        except BaseException:
+            # BaseExceptions can be raised when a socket send operation is not
+            # finished, e.g. due to a timeout.  Ideally, a caller could then re-try
+            # to send un-sent data. However, the send_packed_command() API
+            # does not support it so there is no point in keeping the connection open.
             await self.disconnect(nowait=True)
             raise
 
@@ -820,6 +824,8 @@ async def read_response(
         self,
         disable_decoding: bool = False,
         timeout: Optional[float] = None,
+        *,
+        disconnect_on_error: bool = True,
     ):
         """Read the response from a previously sent command"""
         read_timeout = timeout if timeout is not None else self.socket_timeout
@@ -835,22 +841,24 @@ async def read_response(
                 )
         except asyncio.TimeoutError:
             if timeout is not None:
-                # user requested timeout, return None
+                # user requested timeout, return None. Operation can be retried
                 return None
             # it was a self.socket_timeout error.
-            await self.disconnect(nowait=True)
+            if disconnect_on_error:
+                await self.disconnect(nowait=True)
             raise TimeoutError(f"Timeout reading from {self.host}:{self.port}")
         except OSError as e:
-            await self.disconnect(nowait=True)
+            if disconnect_on_error:
+                await self.disconnect(nowait=True)
             raise ConnectionError(
                 f"Error while reading from {self.host}:{self.port} : {e.args}"
             )
-        except asyncio.CancelledError:
-            # need this check for 3.7, where CancelledError
-            # is subclass of Exception, not BaseException
-            raise
-        except Exception:
-            await self.disconnect(nowait=True)
+        except BaseException:
+            # Also by default close in case of BaseException.  A lot of code
+            # relies on this behaviour when doing Command/Response pairs.
+            # See #1128.
+            if disconnect_on_error:
+                await self.disconnect(nowait=True)
             raise
 
         if self.health_check_interval:

redis/client.py

@@ -1539,7 +1539,7 @@ def try_read():
                     return None
             else:
                 conn.connect()
-            return conn.read_response()
+            return conn.read_response(disconnect_on_error=False)
 
         response = self._execute(conn, try_read)
 

redis/connection.py

@@ -816,7 +816,11 @@ def send_packed_command(self, command, check_health=True):
                 errno = e.args[0]
                 errmsg = e.args[1]
             raise ConnectionError(f"Error {errno} while writing to socket. {errmsg}.")
-        except Exception:
+        except BaseException:
+            # BaseExceptions can be raised when a socket send operation is not
+            # finished, e.g. due to a timeout.  Ideally, a caller could then re-try
+            # to send un-sent data. However, the send_packed_command() API
+            # does not support it so there is no point in keeping the connection open.
             self.disconnect()
             raise
 
@@ -840,23 +844,31 @@ def can_read(self, timeout=0):
             self.disconnect()
             raise ConnectionError(f"Error while reading from {host_error}: {e.args}")
 
-    def read_response(self, disable_decoding=False):
+    def read_response(
+        self, disable_decoding=False, *, disconnect_on_error: bool = True
+    ):
         """Read the response from a previously sent command"""
 
         host_error = self._host_error()
 
         try:
             response = self._parser.read_response(disable_decoding=disable_decoding)
         except socket.timeout:
-            self.disconnect()
+            if disconnect_on_error:
+                self.disconnect()
             raise TimeoutError(f"Timeout reading from {host_error}")
         except OSError as e:
-            self.disconnect()
+            if disconnect_on_error:
+                self.disconnect()
             raise ConnectionError(
                 f"Error while reading from {host_error}" f" : {e.args}"
             )
-        except Exception:
-            self.disconnect()
+        except BaseException:
+            # Also by default close in case of BaseException.  A lot of code
+            # relies on this behaviour when doing Command/Response pairs.
+            # See #1128.
+            if disconnect_on_error:
+                self.disconnect()
             raise
 
         if self.health_check_interval:

tests/test_asyncio/test_commands.py

@@ -1,9 +1,11 @@
 """
 Tests async overrides of commands from their mixins
 """
+import asyncio
 import binascii
 import datetime
 import re
+import sys
 from string import ascii_letters
 
 import pytest
@@ -18,6 +20,11 @@
     skip_unless_arch_bits,
 )
 
+if sys.version_info >= (3, 11, 3):
+    from asyncio import timeout as async_timeout
+else:
+    from async_timeout import timeout as async_timeout
+
 REDIS_6_VERSION = "5.9.0"
 
 
@@ -2999,6 +3006,37 @@ async def test_module_list(self, r: redis.Redis):
         for x in await r.module_list():
             assert isinstance(x, dict)
 
+    @pytest.mark.onlynoncluster
+    async def test_interrupted_command(self, r: redis.Redis):
+        """
+        Regression test for issue #1128:  An Un-handled BaseException
+        will leave the socket with un-read response to a previous
+        command.
+        """
+        ready = asyncio.Event()
+
+        async def helper():
+            with pytest.raises(asyncio.CancelledError):
+                # blocking pop
+                ready.set()
+                await r.brpop(["nonexist"])
+            # If the following is not done, further Timout operations will fail,
+            # because the timeout won't catch its Cancelled Error if the task
+            # has a pending cancel.  Python documentation probably should reflect this.
+            if sys.version_info >= (3, 11):
+                asyncio.current_task().uncancel()
+            # if all is well, we can continue.  The following should not hang.
+            await r.set("status", "down")
+
+        task = asyncio.create_task(helper())
+        await ready.wait()
+        await asyncio.sleep(0.01)
+        # the task is now sleeping, lets send it an exception
+        task.cancel()
+        # If all is well, the task should finish right away, otherwise fail with Timeout
+        async with async_timeout(0.1):
+            await task
+
 
 @pytest.mark.onlynoncluster
 class TestBinarySave:

tests/test_asyncio/test_connection.py

@@ -137,7 +137,7 @@ async def test_connection_parse_response_resume(r: redis.Redis):
     conn._parser._stream = MockStream(message, interrupt_every=2)
     for i in range(100):
         try:
-            response = await conn.read_response()
+            response = await conn.read_response(disconnect_on_error=False)
             break
         except MockStream.TestError:
             pass