Hitless upgrade support implementation for synchronous Redis client.

[petyaslavova]

Pull Request check-list

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Description of change

Hitless upgrade support implementation for synchronous Redis client.

[vladvildanov]

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

[petyaslavova]

Done.

[vladvildanov]

The same here, could it be more generic?

[petyaslavova]

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)

[petyaslavova]

I refactored the code, and now there are two more generic methods: update_connection_kwargs and update_connections_settings, that can be further extended if needed.

[vladvildanov]

This will be not needed if update_connections_tmp_settings will be more generic

[petyaslavova]

@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.

[petyaslavova]

Done.

[vladvildanov]

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?

[petyaslavova]

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 :)

[Copilot]

Pull Request Overview

This PR implements hitless upgrade support for the synchronous Redis client by adding maintenance events handling. The implementation allows the Redis client to gracefully handle cluster rebalancing and node migration operations without losing connections or data.

Key changes:

• Added comprehensive maintenance events handling infrastructure for MOVING, MIGRATING, and MIGRATED events
• Implemented connection pool management for hitless upgrades during cluster maintenance
• Enhanced Redis client with maintenance events configuration and handlers

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
redis/maintenance_events.py	Core maintenance events classes and handlers for processing cluster rebalancing notifications
redis/connection.py	Enhanced connection and pool classes with maintenance state management and proactive reconnection support
redis/client.py	Updated Redis client to support maintenance events configuration and handle connection reconnection during maintenance
redis/_parsers/base.py	Extended parsers to handle maintenance-related push notifications (MOVING, MIGRATING, MIGRATED)
redis/_parsers/resp3.py	Updated RESP3 parser to properly handle push notifications during maintenance events
redis/_parsers/hiredis.py	Updated Hiredis parser to support maintenance event push notifications
tests/test_maintenance_events_handling.py	Comprehensive integration tests for maintenance events handling with mocked Redis protocol
tests/test_maintenance_events.py	Unit tests for maintenance event classes and handlers
tests/test_connection_pool.py	Minor test updates to support new connection pool functionality

Comments suppressed due to low confidence (2)

redis/connection.py:385

• The parser is being set before protocol-specific configurations are applied. Line 407 shows that RESP3Parser is set when protocol is 3, but the initial parser setup happens before this check. This could lead to incorrect parser being used for maintenance events.

        self.health_check_interval = health_check_interval

redis/connection.py:381

• This line appears to be indented incorrectly. The if statement at line 380 should control this block, but the indentation suggests it's not properly nested within the conditional block.

            # Update the retry's supported errors with the specified errors

[Copilot]

[nitpick] The RESP3 protocol format is hardcoded with escape sequences. Consider using a constant or helper function to construct these protocol messages to improve readability and maintainability.

Suggested change

	response = moving_push.encode() + response
	migrating_push = make_resp3_push_message([
	("bulk", "MIGRATING"),
	("int", "10"),
	])
	response = migrating_push + response
	elif b"key_receive_migrated_" in data or b"key_receive_migrated" in data:
	# MIGRATED push message before SET key_receive_migrated_X response
	# Format: >1\r\n$8\r\nMIGRATED\r\n (1 element: MIGRATED)
	migrated_push = make_resp3_push_message([
	("bulk", "MIGRATED"),
	])
	response = migrated_push + response
	elif b"key_receive_moving_" in data:
	# MOVING push message before SET key_receive_moving_X response
	# Format: >3\r\n$6\r\nMOVING\r\n:15\r\n+localhost:6379\r\n (3 elements: MOVING, ttl, host:port)
	# Note: Using + instead of $ to send as simple string instead of bulk string
	moving_push = make_resp3_push_message([
	("bulk", "MOVING"),
	("int", str(MOVING_TIMEOUT)),
	("simple", AFTER_MOVING_ADDRESS),
	])
	response = moving_push + response

[Copilot]

The parameter documentation is incorrect. The parameter name is 'tmp_host_address' but the docstring refers to 'orig_host_address'. This inconsistency could confuse developers.

Suggested change

	:param orig_relax_timeout: The relax timeout to use for the connection.
	:param tmp_host_address: The temporary host address to use for the connection.
	:param tmp_relax_timeout: The relax timeout to use for the connection.

[Copilot]

The parameter documentation is incorrect. The parameter name is 'tmp_relax_timeout' but the docstring refers to 'orig_relax_timeout'. This inconsistency could confuse developers.

Suggested change

	:param orig_relax_timeout: The relax timeout to use for the connection.
	:param tmp_host_address: The temporary host address to use for the connection.
	:param tmp_relax_timeout: The relax timeout to use for the connection.