[WIP/Test Record] Redis single-endpoint cluster support with test-first approach

[yhayase]

Purpose

This PR serves as a development record for implementing Redis single-endpoint cluster support using a test-first approach. This is NOT intended to be merged into this fork, but rather demonstrates the complete development process before submitting to the upstream Laravel repository.

Background

PR laravel#53940 in laravel/framework only fixed putMany() for explicit cluster connection types (PhpRedisClusterConnection, PredisClusterConnection), but did not address:

1. Single-endpoint clusters (e.g., AWS Elasticache Valkey Serverless) that use regular connection classes but run in cluster mode
2. Other methods like many() and flexible() that also perform cross-slot operations
3. Tagged cache flush operations in cluster environments

Test-First Development Process

1. Test Infrastructure Setup

• Created comprehensive integration tests for 4 connection types:
  • phpredis single-endpoint
  • phpredis cluster
  • predis single-endpoint
  • predis cluster
• Built redis-cluster-proxy with INFO command support
• Configured GitHub Actions workflow for CI testing

2. Write Failing Tests First

Initial test run (before implementation): Tests: 33, Errors: 19, Failures: 1

• All cross-slot operations failed as expected
• Demonstrated the problem clearly with concrete test cases

3. Implement to Make Tests Pass

• Implemented server-side cluster mode detection using INFO command
• Added WeakMap-based caching for performance
• Applied cluster fallback to putMany(), many(), and tagged cache operations
• Handled phpredis vs predis response format differences

4. Verify All Tests Pass

Final test run (after implementation): Tests: 33, Assertions: 108 - All passing ✓

• All connection types working correctly
• Tagged cache flush operations working in cluster mode
• Backward compatibility maintained

Implementation Details

Server-side cluster detection:

protected function isServerInClusterMode($connection)
{
    if (! isset($this->clusterModeCache[$connection])) {
        try {
            $info = $connection->client()->info('cluster');
            
            // Handle different formats from phpredis vs predis
            $clusterEnabled = $info['cluster_enabled']
                ?? $info['Cluster']['cluster_enabled']
                ?? null;
                
            $this->clusterModeCache[$connection] = $clusterEnabled == 1;
        } catch (\Exception $e) {
            $this->clusterModeCache[$connection] = false;
        }
    }
    
    return $this->clusterModeCache[$connection];
}

Files Modified:

• src/Illuminate/Cache/RedisStore.php - Core cluster detection and fallback
• src/Illuminate/Cache/RedisTaggedCache.php - Tagged cache flush support

Test Coverage:

• tests/Integration/Cache/RedisSingleEndpointClusterTest.php - 33 tests covering all scenarios
• .github/workflows/redis-cluster.yml - CI workflow for cluster testing

CI Results

✅ All tests passing in GitHub Actions:

• Redis Cluster tests (3 jobs) - All passing
• Main test suite (48+ jobs across PHP 8.2/8.3/8.4, multiple PHPUnit versions, Linux/Windows) - All passing
• Backward compatibility confirmed

Next Steps

This implementation is ready to be submitted as a PR to laravel/framework. The test-first approach ensures:

1. Problem is clearly demonstrated with failing tests before any implementation
2. Solution is validated with passing tests
3. No regressions in existing functionality
4. Comprehensive documentation of the development process

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🤖 This PR demonstrates test-first development and is a preparation record for upstream contribution.