Hitless upgrade support implementation for synchronous Redis client. #3713

petyaslavova · 2025-07-17T12:31:04Z

Pull Request check-list

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Description of change

Hitless upgrade support implementation for synchronous Redis client.

redis/connection.py

redis/maintenance_events.py

redis/_parsers/base.py

tests/test_maintenance_events.py

redis/connection.py

redis/maintenance_events.py

…lient.

… tests for maintenance_events.py file

…tion pool - this should be a separate PR

… Refactored the maintenance events tests not to be multithreaded - we don't need it for those tests.

…ot processed in in Moving state. Tests are updated

…ply them during connect

Copilot

Pull Request Overview

This pull request implements hitless upgrade support for the synchronous Redis client by introducing maintenance event handling capabilities. This feature allows Redis clients to gracefully handle cluster maintenance operations like node migrations and replacements without dropping connections or failing commands.

Key changes include:

Added comprehensive maintenance events framework with event classes and handlers
Extended connection pool to support maintenance states and temporary configurations
Integrated push notification handlers for RESP3 protocol maintenance events

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 9 comments.

Show a summary per file

File	Description
tests/test_maintenance_events_handling.py	Comprehensive integration tests for maintenance events handling with mock sockets
tests/test_maintenance_events.py	Unit tests for maintenance event classes, configurations, and handlers
tests/test_connection_pool.py	Added `should_reconnect` method to test connection mock
redis/maintenance_events.py	Core maintenance events framework with event classes, configurations, and handlers
redis/connection.py	Enhanced connection and pool classes with maintenance event support and state management
redis/client.py	Integrated maintenance events configuration into Redis client initialization
redis/asyncio/connection.py	Added maintenance mode support for async blocking connection pool
redis/_parsers/resp3.py	Enhanced RESP3 parser with push notification handlers for maintenance events
redis/_parsers/hiredis.py	Added maintenance event push handlers to hiredis parser
redis/_parsers/base.py	Added maintenance event parsing logic and handler registration methods

redis/maintenance_events.py

tests/test_maintenance_events_handling.py

Copilot · 2025-07-26T10:13:07Z

redis/connection.py

+
+    def set_tmp_settings(
+        self,
+        tmp_host_address: Optional[Union[str, object]] = SENTINEL,


Using SENTINEL as a default value but SENTINEL is not defined in this scope. This could cause a NameError.

vladvildanov · 2025-07-29T08:51:45Z

redis/connection.py

@@ -1646,6 +1815,154 @@ def re_auth_callback(self, token: TokenInterface):
            for conn in self._in_use_connections:
                conn.set_re_auth_token(token)

+    def update_connection_kwargs_with_tmp_settings(


Could you make it more generic? Something like update_connection_kwargs(**kwargs)

vladvildanov · 2025-07-29T08:52:45Z

redis/connection.py

+        self.connection_kwargs.update({"tmp_host_address": tmp_host_address})
+        self.connection_kwargs.update({"tmp_relax_timeout": tmp_relax_timeout})
+
+    def update_connections_tmp_settings(


The same here, could it be more generic?

Now I see why I didn't understand the next comment :) This is an old function that has been removed and split into two separate functions.
I'll see how will be appropriate to combine some of the into more generic ones or which of the newly added ones can be transformed into more generic ones(like the one mentioned above --> update_connection_kwargs)

vladvildanov · 2025-07-29T08:56:56Z

redis/connection.py

+                conn, tmp_host_address, tmp_relax_timeout
+            )
+
+    def update_connections_current_timeout(


This will be not needed if update_connections_tmp_settings will be more generic

@vladvildanov I didn’t quite understand this one — do you mean having a single generic method that handles all possible updates to object properties, including the socket timeout update for already connected connections?

I intentionally separated them to make it easier to follow what exactly gets updated during notification handling — specifically, whether we’re only updating properties used during connect, or actually changing the behavior of already established socket connections.

redis/asyncio/connection.py

vladvildanov · 2025-07-29T09:19:30Z

redis/connection.py

+            connections_in_queue = {conn for conn in self.pool.queue if conn}
+            for conn in self._connections:
+                if conn not in connections_in_queue:
+                    if address_type_to_match == "connected":


There's a lot of duplicate of this part:

if address_type_to_match == "connected": if matching_address and conn.getpeername() != matching_address: continue

Maybe it makes to create a method that filter connections by this criteria and returns filtered?

I wanted to iterate over the different lists once and not create additional lists holding references to the connection objects that match the filter, so I think it will be better to create a new helper method that just checks if the connection should be updated or not. You are right - it is a lot of code duplication :)

petyaslavova requested a review from Copilot July 17, 2025 12:31

petyaslavova added feature New feature experimental labels Jul 17, 2025

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petyaslavova force-pushed the ps_hitless_upgrade_sync_redis branch 4 times, most recently from 0304da5 to ee27bd2 Compare July 22, 2025 16:51

petyaslavova commented Jul 24, 2025

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vladvildanov reviewed Jul 24, 2025

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petyaslavova added 14 commits July 24, 2025 16:40

Handling of topology update push notifications for Standalone Redis c…

092e33b

…lient.

Adding sequence id to the maintenance push notifications. Adding unit…

41a199e

… tests for maintenance_events.py file

Adding integration-like tests for migrating/migrated events handling

63d0c45

Removed unused imports

5c71733

Revert changing of the default retry object initialization for connec…

96c6e5d

…tion pool - this should be a separate PR

Complete migrating/migrated integration-like tests

8691475

Adding moving integration-like tests

7b57a22

Fixed BlockingConnectionPool locking strategy. Removed debug logging.…

bed2e40

… Refactored the maintenance events tests not to be multithreaded - we don't need it for those tests.

Fixing linters

0744ee5

Applying Copilot's comments

4c536f3

Fixed type annotations not compatible with older python versions

6768d5d

Add a few more tests and fix pool mock for python 3.9

ce31ec7

Adding maintenance state to connections. Migrating and Migrated are n…

d73cd35

…ot processed in in Moving state. Tests are updated

Refactored the tmp host address and timeout storing and the way to ap…

788cf52

…ply them during connect

petyaslavova force-pushed the ps_hitless_upgrade_sync_redis branch from ee27bd2 to 0f9734c Compare July 24, 2025 13:43

Apply review comments

6d496f0

petyaslavova force-pushed the ps_hitless_upgrade_sync_redis branch from 0f9734c to 6d496f0 Compare July 24, 2025 13:45

Applying moving/moved only on connections to the same proxy.

2d3731f

petyaslavova requested a review from Copilot July 26, 2025 10:11

Copilot AI reviewed Jul 26, 2025

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vladvildanov requested changes Jul 29, 2025

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petyaslavova added 2 commits August 8, 2025 14:24

Merge branch 'master' into ps_hitless_upgrade_sync_redis

a82cbfe

Applying review comments.

2cdfa75

Hitless upgrade support implementation for synchronous Redis client. #3713

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petyaslavova commented Jul 17, 2025

Pull Request check-list

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Pull Request Overview

Reviewed Changes

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Copilot AI Jul 26, 2025

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