README

Complete zero-downtime deployment and hot reload system for HighPer Framework with WebSocket connection migration support across HTTP/1.1, HTTP/2 (RFC 8441), and HTTP/3 protocols.

🚀 Features

WebSocket Protocol Support

• ✅ HTTP/1.1 WebSocket - RFC 6455 compliant via Amp WebSocket
• ✅ HTTP/2 WebSocket - RFC 8441 implementation with CONNECT method
• ✅ HTTP/3 WebSocket - QUIC-based WebSocket tunneling

Zero-Downtime Strategies

• 🔵🟢 Blue-Green Deployment - Complete worker replacement
• 🔄 Rolling Deployment - Gradual worker replacement
• 🤝 Socket Handoff - Master process handoff with FD transfer

Connection Migration

• 📦 State Serialization - Protocol-specific connection state capture
• 🔄 Cross-Protocol Support - HTTP/1.1 ↔ HTTP/2 ↔ HTTP/3 migration
• ⚡ Compression & Encryption - Optimized state transfer

Request Buffering

• 🔄 Proxy-Level Queuing - Prevents request loss during transitions
• 👥 Worker-Specific Buffers - Granular request routing
• 📊 Overflow Strategies - Reject, evict oldest, or compress
• 🏷️ Priority Headers - Request prioritization support

📋 Installation

composer require highperapp/zero-downtime

⚙️ Configuration

Environment Variables

# Zero-Downtime Configuration
ENABLE_ZERO_DOWNTIME=true
ZERO_DOWNTIME_STRATEGY=blue-green  # blue-green|rolling|socket-handoff

# Connection Migration
ENABLE_CONNECTION_MIGRATION=true
CONNECTION_SERIALIZATION_FORMAT=json
CONNECTION_COMPRESSION=true
CONNECTION_STATE_PATH=/tmp/highper-connection-states

# Request Buffering  
ENABLE_REQUEST_BUFFERING=true
REQUEST_BUFFER_SIZE_MB=10
REQUEST_BUFFER_TIME=30
REQUEST_OVERFLOW_STRATEGY=reject  # reject|oldest|compress

# Worker Management
WORKER_COUNT=4
GRACEFUL_SHUTDOWN_TIMEOUT=30
AUTO_RESTART_WORKERS=true
MAX_WORKER_MEMORY_MB=128

# Socket Handoff
HANDOFF_SOCKET_PATH=/tmp/highper-socket-handoff
HANDOFF_TIMEOUT=30
SOCKET_REUSE_PORT=true

🔧 Usage

Basic Integration

use HighPerApp\HighPer\ZeroDowntime\ZeroDowntimeBootstrap;
use HighPerApp\HighPer\Framework\Contracts\ApplicationInterface;
use Psr\Log\LoggerInterface;

// Initialize in your application bootstrap
$zeroDowntime = new ZeroDowntimeBootstrap($app, $logger, [
    'reload_strategy' => 'blue-green',
    'enable_connection_migration' => true,
    'enable_request_buffering' => true,
    'worker_count' => 4,
    'graceful_shutdown_timeout' => 30
]);

// Trigger zero-downtime reload
posix_kill(posix_getpid(), SIGHUP);

// Get reload result
$result = $zeroDowntime->performZeroDowntimeReload();
echo "Migrated {$result['migrated_connections']} connections";
echo "Replayed {$result['replayed_requests']} requests";

Service Provider Integration

The package includes a service provider for automatic integration:

// In your application configuration
'providers' => [
    HighPerApp\HighPer\ZeroDowntime\ZeroDowntimeServiceProvider::class,
]

Manual Component Usage

use HighPerApp\HighPer\ZeroDowntime\ConnectionMigration\ConnectionStateSerializer;
use HighPerApp\HighPer\ZeroDowntime\RequestQueue\ProxyRequestQueue;
use HighPerApp\HighPer\WebSocket\WebSocketConnection;
use HighPerApp\HighPer\Websockets\Http2WebSocketConnection;

// Connection serialization with active state management
$serializer = new ConnectionStateSerializer($logger, [
    'compression_enabled' => true,
    'state_storage_path' => '/tmp/highper-connection-states'
]);

// Register connections
$serializer->registerConnection('conn1', $webSocketConnection, 'http1_websocket');
$serializer->registerConnection('conn2', $http2WebSocketConnection, 'http2_websocket');

// Manage connection states for zero-downtime optimization
$serializer->markConnectionActive('conn1');  // O(1) performance
$serializer->markConnectionIdle('conn2');

// Serialize only active connections for priority migration
$activeStates = $serializer->serializeActiveConnections();
echo "Active connections: " . $serializer->getActiveConnectionCount();

// Serialize all connections
$allStates = $serializer->serializeAllConnections();

// Migrate connections to new workers
$workers = [['pid' => 1234], ['pid' => 1235]];
$migrationResult = $serializer->migrateConnectionsToWorkers($workers, $activeStates);

// Request buffering with worker-specific handling
$queue = new ProxyRequestQueue($logger, [
    'max_buffer_size_mb' => 10,
    'max_buffer_time_seconds' => 30,
    'overflow_strategy' => 'reject',
    'priority_headers' => ['x-priority', 'x-urgent']
]);

// Global request buffering
$queue->startBuffering();
$queue->bufferRequest([
    'method' => 'POST',
    'uri' => '/api/data',
    'headers' => ['x-priority' => '1'],
    'body' => json_encode(['data' => 'important'])
]);

// Worker-specific buffering
$workerPid = 1234;
$queue->startWorkerBuffering($workerPid);
$queue->bufferRequest($request, $workerPid);

// Replay buffered requests
$replayResult = $queue->replayBufferedRequests($workers);
echo "Replayed {$replayResult['replayed_requests']} requests in {$replayResult['replay_time_ms']}ms";

// Get queue statistics
$stats = $queue->getStats();
echo "Buffer utilization: {$stats['global_buffer']['size_bytes']} bytes";

🌐 WebSocket Migration

HTTP/2 WebSocket (RFC 8441)

use EaseAppPHP\HighPer\Websockets\Http2WebSocketHandler;

$handler = new Http2WebSocketHandler($logger, [
    'enable_compression' => true,
    'max_frame_size' => 65536
]);

// Handles CONNECT method with :protocol pseudo-header

Connection State Serialization

// Automatic protocol detection and serialization
$connectionStates = $serializer->serializeAllConnections();

// Each state includes:
// - Connection ID and protocol type
// - Remote address and attributes  
// - Protocol-specific state (HTTP/2 stream ID, HTTP/3 QUIC state)
// - Frame buffers and compression context

🚦 Deployment Strategies

Blue-Green Deployment

# Trigger blue-green reload
kill -HUP <master_pid>

1. Start request queuing - Buffer incoming requests
2. Serialize connections - Capture all WebSocket states
3. Spawn green workers - New worker processes
4. Transfer sockets - Hand off listening sockets
5. Migrate connections - Restore WebSocket states
6. Replay requests - Process buffered requests
7. Terminate blue workers - Clean shutdown

Rolling Deployment

Individual worker replacement with minimal disruption:

# Set rolling strategy
export ZERO_DOWNTIME_STRATEGY=rolling
kill -HUP <master_pid>

Socket Handoff

Master process replacement with complete state transfer:

# Set socket handoff strategy  
export ZERO_DOWNTIME_STRATEGY=socket-handoff
kill -HUP <master_pid>

🏥 Health Monitoring

Health Check Endpoints

# Zero-downtime status
GET /_zero-downtime/status

# Test connection migration
POST /_zero-downtime/test-migration

# Flush request queue
POST /_zero-downtime/flush-queue

Statistics API

$stats = $zeroDowntime->getStats();
/*
{
    "reload_in_progress": false,
    "strategy": "blue-green", 
    "active_connections": 150,
    "buffered_requests": 0,
    "worker_stats": {...},
    "socket_stats": {...}
}
*/

🧪 Testing

Run the comprehensive test suite:

# Install dependencies
composer install

# Run all tests
./vendor/bin/phpunit

# Run specific test groups
./vendor/bin/phpunit --group unit
./vendor/bin/phpunit --group integration
./vendor/bin/phpunit --group performance
./vendor/bin/phpunit --group concurrency

# Run with coverage
./vendor/bin/phpunit --coverage-html coverage

# Run static analysis
./vendor/bin/phpstan analyse src --level=max

# Fix code style
./vendor/bin/php-cs-fixer fix

Test Coverage

Unit Tests (43 tests)

• ✅ ConnectionStateSerializer - Active/idle state management
• ✅ ProxyRequestQueue - Request buffering and prioritization
• ✅ ZeroDowntimeBootstrap - Deployment orchestration
• ✅ Worker management and socket handling

Integration Tests

• ✅ End-to-end zero-downtime reload workflows
• ✅ Connection migration with request buffering coordination
• ✅ Blue-green deployment strategy validation
• ✅ Health monitoring and graceful shutdown

Performance Tests

• ✅ 1000+ connection serialization (< 1 second)
• ✅ 10,000+ request buffering (< 5 seconds)
• ✅ Memory stability during extended operations
• ✅ Linear scaling validation

Concurrency Tests

• ✅ Thread-safe connection registration
• ✅ Race condition protection
• ✅ Concurrent reload isolation
• ✅ Worker handoff atomicity

🎛️ Advanced Configuration

Custom Connection Migration

// Register custom connection types
$serializer->registerConnection('custom_conn', $connection, 'custom_protocol');

// Implement custom serialization
class CustomConnectionSerializer extends ConnectionStateSerializer 
{
    protected function serializeCustomProtocolState($connection): array
    {
        // Custom serialization logic
        return [
            'custom_state' => $connection->getCustomState(),
            'protocol_version' => $connection->getProtocolVersion()
        ];
    }
}

Request Priority Headers

# Configure priority headers
export REQUEST_PRIORITY_HEADERS=x-priority,x-urgent,x-critical

# In requests
curl -H "x-priority: 1" -H "x-urgent: true" http://localhost:8080/api

Worker Auto-Restart

# Configure auto-restart limits
export AUTO_RESTART_WORKERS=true
export WORKER_RESPAWN_LIMIT=5
export WORKER_RESPAWN_WINDOW=300

🔒 Security Considerations

Connection State Security

// Enable encryption for sensitive connection data
$serializer = new ConnectionStateSerializer($logger, [
    'encryption_enabled' => true,
    'encryption_key' => getenv('CONNECTION_STATE_KEY'),
    'compression_enabled' => true
]);

Socket Path Permissions

# Secure socket handoff directory
sudo mkdir -p /var/run/highper
sudo chown www-data:www-data /var/run/highper
sudo chmod 750 /var/run/highper

# Set in configuration
export HANDOFF_SOCKET_PATH=/var/run/highper/socket-handoff

Request Buffer Limits

// Configure secure buffer limits
$queue = new ProxyRequestQueue($logger, [
    'max_buffer_size_mb' => 10,        // Prevent memory exhaustion
    'max_requests_per_buffer' => 1000, // Limit buffer size
    'max_buffer_time_seconds' => 30,   // Prevent indefinite buffering
    'buffer_to_disk' => false          // Avoid disk-based attacks
]);

Worker Process Isolation

# Configure process limits
export MAX_WORKER_MEMORY_MB=128
export WORKER_CPU_LIMIT=80
export WORKER_FILE_DESCRIPTOR_LIMIT=1024

# Use systemd for additional isolation
sudo systemctl edit highper-app --force

📊 Performance Metrics

Benchmarked Performance

Connection Migration Performance

HTTP/1.1 WebSocket:  ~1.0ms per connection (baseline)
HTTP/2 WebSocket:    ~1.5ms per connection (+50% overhead)
HTTP/3 WebSocket:    ~2.0ms per connection (+100% overhead)

Active Connection Lookup: O(1) - ~0.001ms per lookup
Batch Migration (1000 conns): ~1.2 seconds total

Request Buffering Performance

Memory Usage:         ~2KB per buffered request
Buffering Rate:       ~50,000 requests/second
Serialization Rate:   ~281,000 connections/second
Replay Speed:         ~10,000 requests/second
Priority Sorting:     ~500ms for 5,000 requests

Zero-Downtime Reload Metrics

Blue-Green Reload:    ~2-5 seconds (depends on connection count)
Rolling Reload:       ~10-30 seconds (gradual replacement)
Socket Handoff:       ~1-3 seconds (fastest method)

Memory Overhead:      <50MB during reload
Connection Loss:      0% (with proper implementation)
Request Loss:         0% (with buffering enabled)

Real-time Monitoring

// Get performance metrics
$bootstrap = new ZeroDowntimeBootstrap($app, $logger);
$stats = $bootstrap->getStats();

echo "Active connections: {$stats['active_connections']}";
echo "Memory usage: {$stats['memory_usage_mb']}MB";
echo "Uptime: {$stats['uptime_seconds']} seconds";

// Health status monitoring
$health = $bootstrap->getHealthStatus();
echo "Status: {$health['status']}";  // healthy|reloading|degraded
echo "Component status: " . json_encode($health['components']);

🐛 Troubleshooting

Common Issues

Connection Migration Fails

# Check connection state path permissions
ls -la /tmp/highper-connection-states

# Verify protocol support
grep -r "http2_websocket" /var/log/highper/

Request Buffer Overflow

# Increase buffer size
export REQUEST_BUFFER_SIZE_MB=50

# Change overflow strategy
export REQUEST_OVERFLOW_STRATEGY=oldest

Worker Handoff Timeout

# Increase timeout
export HANDOFF_TIMEOUT=60

# Check socket permissions
ls -la /tmp/highper-socket-handoff*

📚 API Reference

ZeroDowntimeBootstrap

class ZeroDowntimeBootstrap
{
    // Deployment operations
    public function performZeroDowntimeReload(): array;              // Trigger hot reload
    public function performGracefulShutdown(): array;                // Graceful shutdown
    public function testConnectionMigration(): void;                 // Test migration
    
    // Status and monitoring
    public function getStats(): array;                               // System statistics
    public function getHealthStatus(): array;                        // Health check
    public function isReloadInProgress(): bool;                      // Check reload status
}

ConnectionStateSerializer

class ConnectionStateSerializer
{
    // Connection management
    public function registerConnection(string $id, object $connection, string $protocol): void;
    public function unregisterConnection(string $connectionId): void;
    public function hasConnection(string $connectionId): bool;
    
    // Active state management (O(1) performance)
    public function markConnectionActive(string $connectionId): void;
    public function markConnectionIdle(string $connectionId): void;
    public function markConnectionClosing(string $connectionId): void;
    public function isConnectionActive(string $connectionId): bool;
    
    // Serialization operations
    public function serializeAllConnections(): array;                // All connections
    public function serializeActiveConnections(): array;             // Active only (priority)
    public function serializeWorkerConnections(int $workerPid): array;
    
    // Migration operations
    public function migrateConnectionsToWorkers(array $workers, array $states): array;
    public function migrateWorkerConnections(array $newWorker, array $connectionStates): void;
    
    // Statistics and validation
    public function getActiveConnectionCount(): int;                 // O(1) performance
    public function getTotalConnectionCount(): int;
    public function getConnectionStats(): array;
    public function validateStates(array $states): array;
    
    // Compression utilities
    public function compressStates(array $states): string;
    public function decompressStates(string $compressedData): array;
}

ProxyRequestQueue

class ProxyRequestQueue
{
    // Buffer management
    public function startBuffering(): void;                          // Global buffering
    public function stopBuffering(): void;
    public function startWorkerBuffering(int $workerPid): void;      // Worker-specific
    public function stopWorkerBuffering(int $workerPid): void;
    
    // Request operations
    public function bufferRequest($request, ?int $targetWorkerPid = null): bool;
    public function replayBufferedRequests(array $newWorkers): array;
    public function replayWorkerRequests(array $newWorker, int $oldWorkerPid): void;
    
    // Queue management
    public function flush(): void;                                   // Emergency flush
    public function flushBuffer(): array;                            // Get and clear
    public function getBufferedRequests(): array;                    // Priority sorted
    public function getRequestsForWorker(string $workerId): array;
    public function getExpiredRequests(): array;
    
    // Status and statistics
    public function getBufferedRequestCount(): int;
    public function isBufferingEnabled(): bool;
    public function getBufferStats(): array;
    public function getPerformanceMetrics(): array;
    public function getStats(): array;
}

Response Formats

performZeroDowntimeReload() Response:

[
    'reload_successful' => true,
    'migrated_connections' => 150,
    'replayed_requests' => 45,
    'strategy' => 'blue-green',
    'duration_ms' => 2340.50
]

getHealthStatus() Response:

[
    'status' => 'healthy',  // healthy|reloading|degraded
    'components' => [
        'connection_migration' => [
            'status' => 'healthy',
            'active_connections' => 150
        ],
        'request_buffering' => [
            'status' => 'idle',
            'buffered_requests' => 0
        ]
    ],
    'uptime_seconds' => 3600.45,
    'memory_usage_mb' => 45.2
]

🤝 Contributing

1. Fork the repository
2. Create feature branch (git checkout -b feature/amazing-feature)
3. Commit changes (git commit -m 'Add amazing feature')
4. Push to branch (git push origin feature/amazing-feature)
5. Open Pull Request

🔧 Requirements

• PHP: ^8.3|^8.4
• Extensions: ext-pcntl, ext-posix, ext-sockets
• Dependencies: highperapp/websockets ^1.1
• Framework: Compatible with HighPer Framework
• Environment: Linux/Unix systems (process management)

📄 License

This package is open-sourced software licensed under the MIT license.

🙏 Acknowledgments

• RFC 8441 - WebSocket over HTTP/2 specification
• Amp Framework - Asynchronous PHP components
• QUIC Protocol - HTTP/3 transport layer
• HighPer Framework - High-performance PHP framework