[automatic failover] feat: Add MultiDbClient with multi-endpoint failover and circuit breaker support

[ggivo]

This PR introduces ResilientRedisClient, a new high-availability Redis client that extends UnifiedJedis with automatic failover capabilities across multiple weighted endpoints.

Key Features

• Multi-Endpoint Support: Configure multiple Redis endpoints with individual weights
• Automatic Failover: Seamless switching to backup endpoints when the primary becomes unavailable
• Circuit Breaker Pattern: Built-in circuit breaker with configurable thresholds
• Health Monitoring: Continuous health checks with automatic failback to recovered endpoints
• Dynamic Management: Add/remove endpoints at runtime without client restart
• Event-Driven Monitoring: Listen to cluster switch events for alerting and observability

Components Added

• ResilientRedisClient - Main client class extending UnifiedJedis
• ResilientClientBuilder - Fluent builder for client configuration

Usage Example

class MultiDbClientUsageExample {

    public static void main(String[] args) {
        HostAndPort east = new HostAndPort("localhost", 29379);
        RedisCredentials credentialsEast = new DefaultRedisCredentials("default", "secretEast");

        HostAndPort west = new HostAndPort("localhost", 29380);
        RedisCredentials credentialsWest = new DefaultRedisCredentials("default", "secretWest");


        MultiDbClient client = MultiDbClient.builder()
                .multiDbConfig(
                        MultiClusterClientConfig.builder()
                                .endpoint(
                                        ClusterConfig.builder(
                                                        east,
                                                        DefaultJedisClientConfig.builder().credentials(credentialsEast).build())
                                                .weight(100.0f)
                                                .build())
                                .endpoint(ClusterConfig.builder(
                                                west,
                                                DefaultJedisClientConfig.builder().credentials(credentialsWest).build())
                                        .weight(50.0f).build())
                                .circuitBreakerFailureRateThreshold(50.0f)
                                .retryMaxAttempts(3)
                                .build()
                )
                .databaseSwitchListener(event -> System.out.println("Switched to: " + event.getEndpoint()))
                .build();

        String infoEast = client.info("server");
        System.out.println( "Before endpoint switch : Info East: " + infoEast);

        client.setActiveDatabaseEndpoint(west);

        String infoWest = client.info("server");
        System.out.println( "Before endpoint switch : Info West: " + infoWest);

        client.close();
    }

}

Testing

• Integration test

Based on PR : #4263.
Important changes in commit : feat: introduce ResilientRedisClient with multi-endpoint failover sup…

Closes #4299

[github-actions]

Test Results

   283 files  +1     283 suites  +1   11m 24s ⏱️ -1s
10 076 tests +8  10 031 ✅ +8  45 💤 ±0  0 ❌ ±0 
 2 714 runs  +8   2 714 ✅ +8   0 💤 ±0  0 ❌ ±0 

Results for commit f75c545. ± Comparison against base commit 11308f0.

♻️ This comment has been updated with latest results.

[uglide]

We need to do a massive renaming to align the naming with the design:

• ResilientClient -> MultiDbClient (builder, tests, etc)
• multiClusterConfig -> multiDbConfig
• ClusterConfig -> DatabaseConfig
• clusterSwitchListener -> databaseSwitchListener
• setActiveEndpoint -> setActiveDatabaseEndpoint

[ggivo]

We need to do a massive renaming to align the naming with the design:

• ResilientClient -> MultiDbClient (builder, tests, etc)
• multiClusterConfig -> multiDbConfig
• ClusterConfig -> DatabaseConfig
• clusterSwitchListener -> databaseSwitchListener
• setActiveEndpoint -> setActiveDatabaseEndpoint

Some renaming will conflict with -> #4295
Will do one round (updating newly introduces Client/Builders methods)

And another one after #4295 is merged for remaining changes ( ClusterConfig -> DatabaseConfig ...)

[atakavci]

LGTM!