[automatic failover] Add Dynamic Weight Management for Redis Multi-Database Connections

[atakavci]

Summary

Adds the ability to dynamically update database weights at runtime for multi-database Redis connections, enabling flexible endpoint priority adjustments without reconnection.

Changes

API Enhancements

• Added setWeight(float) method to RedisDatabase interface
• Made weight field mutable in RedisDatabaseImpl

Documentation Updates

• Clarified that weight is used for "endpoint priority" rather than "load balancing" across javadocs
• Updated terminology in DatabaseConfig, BaseRedisMultiDbConnection, and RedisDatabase

Test Coverage

• Added 6 integration tests for weight management operations
• Added 7 unit tests covering edge cases (zero, negative, max values, multiple updates)
• Tests verify weight retrieval, updates, and multi-database scenarios

Use Case

Allows runtime adjustment of database priorities for failover scenarios without requiring connection recreation.

[Copilot]

Pull request overview

Adds runtime weight updates for multi-database Redis failover connections so endpoint priority can be adjusted without recreating connections.

Changes:

• Extends RedisDatabase with a runtime setWeight(float) API and makes RedisDatabaseImpl.weight mutable.
• Updates terminology in Javadocs from “load balancing” to “endpoint priority”.
• Adds unit/integration tests covering weight retrieval and updates.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/main/java/io/lettuce/core/failover/api/RedisDatabase.java	Adds setWeight(float) to the public database API.
src/main/java/io/lettuce/core/failover/RedisDatabaseImpl.java	Makes weight mutable and implements setWeight.
src/main/java/io/lettuce/core/failover/api/DatabaseConfig.java	Updates Javadocs to reflect endpoint-priority semantics.
src/main/java/io/lettuce/core/failover/api/BaseRedisMultiDbConnection.java	Updates addDatabase parameter documentation for endpoint priority.
src/test/java/io/lettuce/core/failover/StatefulRedisMultiDbConnectionImplUnitTests.java	Adds unit tests for weight get/set and edge values.
src/test/java/io/lettuce/core/failover/StatefulMultiDbConnectionIntegrationTests.java	Adds integration tests for weight operations via connection APIs.
src/test/java/io/lettuce/core/failover/DatabaseConfigBuilderUnitTests.java	Updates example naming/terminology around weights.

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[ggivo]

When adding or removing databases, we evaluate and switch to the database with the highest weight.
However, changing the weights does not currently trigger a re-evaluation or switch. I would expect weight updates to behave similarly to add/remove operations and trigger a switch to the highest-weighted database.

[ggivo]

When adding or removing databases, we evaluate and switch to the database with the highest weight.
However, changing the weights does not currently trigger a re-evaluation or switch. I would expect weight updates to behave similarly to add/remove operations and trigger a switch to the highest-weighted database.

[atakavci]

When adding or removing databases, we evaluate and switch to the database with the highest weight. However, changing the weights does not currently trigger a re-evaluation or switch. I would expect weight updates to behave similarly to add/remove operations and trigger a switch to the highest-weighted database.

@ggivo adding/removing db does not trigger a failback/failover directly. Right now fundamental parts are there to set/switch/failover in case user likes to do so.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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[ggivo]

adding/removing db does not trigger a failback/failover directly. Right now fundamental parts are there to set/switch/failover in case user likes to do so.

@atakavci
Agree.
But this change made me think, if we update the weights of databases, we are missing an API to trigger reevaluation and select the best match.

[ggivo]

LGTM