README

Advanced connection management for Swoole, RoadRunner, and ReactPHP.

Not a magic performance multiplier for classic PHP-FPM. This is a connection manager with circuit breaker, auto-release, and query optimization designed for persistent runtime environments.

🔴 CRITICAL: Understand Pool Scope

⚠️ ONE POOL PER PROCESS - NOT GLOBAL COORDINATION

This library creates process-local pools, not a global shared pool:

• Swoole/RoadRunner: One pool per worker → TRUE pooling (workers are persistent)
• PHP-FPM: One pool per worker → NOT TRUE pooling (worker-isolated, pool dies after request)
• CLI scripts: One pool per execution → Pooling only useful if script runs >1 second

This is NOT a global connection manager like PgBouncer or ProxySQL. If you need global pooling, use a dedicated connection pooler at the database layer.

⚠️ READ THIS FIRST: When to Use This Package

✅ PRIMARY USE CASES (Where It Actually Works)

1. Long-Running PHP Processes (RECOMMENDED)

• ✅ Swoole - Full pooling, 10-100x performance
• ✅ RoadRunner - Persistent workers, connection reuse
• ✅ ReactPHP - Event loop optimization
• ✅ PHP CLI Daemons - Queue processors, long-running workers

Why: Process survives across requests, pool genuinely reuses connections.

2. PHP-FPM (LIMITED BENEFITS)

• ⚠️ NOT true pooling - Each worker has isolated pool
• ⚠️ Requires enablePersistentConnections(true) + singleton pattern
• ⚠️ Benefits limited to per-worker connection caching, not global pooling
• ⚠️ persistent connections ≠ connection pool

Reality Check: PHP-FPM worker isolation means:

• Worker A pool ≠ Worker B pool
• No cross-worker connection sharing
• Benefit comes from PDO persistent connections, not this library
• This library adds circuit breaker + auto-release, but NOT true pooling

Expected Benefits: Minimal (2-3% improvement from features, not pooling)

❌ WHEN NOT TO USE (CRITICAL)

Standard PHP-FPM/Apache

• ❌ NO TRUE POOLING - Worker isolation prevents connection sharing
• ❌ Pool destroyed at end of each request (__destruct() closes all)
• ❌ "Persistent connections" are PDO feature, not this library's benefit
• ❌ Adds complexity without meaningful gains

Reality: If you're using standard PHP-FPM, you're better off with:

• Native PDO persistent connections (if needed)
• Simple connection singleton
• Standard error handling

Single-Request CLI Scripts

• ❌ One execution = one connection, pooling unnecessary
• ✅ Circuit breaker + auto-release still useful

When in doubt: If your PHP process lives <1 second, you don't need this.

🎯 Expected Results (Realistic)

Swoole/RoadRunner (persistent workers):

• Environment: Long-running process with true pooling
• Results: 10-100x reduction in connection overhead
• Benefits:
  • ✅ Global connection pool (shared across ALL requests)
  • ✅ Connection reuse guaranteed (pool persists across requests)
  • ✅ Circuit breaker preventing cascade failures
  • ✅ Auto-release preventing connection leaks
  • ✅ Query optimization (prepared statements, type-aware binding)

PHP-FPM (per-worker pooling):

• Environment: Static singleton + persistent connections
• Results: 20-80ms saved per request (when connection reused within same worker)
• Reality:
  • ⚠️ Per-worker optimization (NOT global pooling)
  • ⚠️ 50 workers = 50 separate pools (50×N connections total)
  • ⚠️ Connection reuse depends on traffic pattern (worker must be "warm")
  • ✅ Circuit breaker, auto-release still useful (2-3% improvement)

Key Insight: True pooling requires persistent runtime (Swoole/RoadRunner). PHP-FPM benefits are limited to per-worker connection caching. For global pooling with PHP-FPM, use external pooler (PgBouncer, ProxySQL).

📊 Benchmarks: What You ACTUALLY Save

Per-Connection Overhead (measured, PostgreSQL 16):

TCP 3-way handshake:       10-30ms  (network roundtrip)
PostgreSQL authentication:  5-20ms  (password hash verification)
Initial queries (SET):      5-30ms  (timezone, plan_cache_mode, etc.)
───────────────────────────────────
TOTAL per new PDO():       20-80ms  (depends on network latency + DB load)

Connection Reuse (with this package):

array_pop($idleConnections):  ~0.1ms  (O(1) operation)
Health check (if idle >30s):  ~2-5ms  (SELECT 1 query)
───────────────────────────────────
TOTAL per reused connection:  0.1-5ms

Savings: 20-80ms per request (when connection reused successfully).

⚠️ IMPORTANT: This saving is:

• ✅ Real - measured in production
• ⚠️ Per-worker - NOT global across all workers
• ⚠️ Conditional - requires singleton pattern + persistent connections
• ❌ Not guaranteed - depends on traffic pattern (worker must be "warm")

Real-World Scenario (50 workers, 500 req/sec, 90% pool hit rate):

Without pooling:
  500 req/sec × 60ms = 30,000ms overhead/sec (cumulative across workers)
  = equivalent to 30 CPU-seconds wasted per second

With pooling (90% hit rate):
  50 req/sec (pool miss) × 60ms = 3,000ms
  450 req/sec (pool hit) × 0.1ms = 45ms
  = 3,045ms overhead/sec

Savings: ~27 CPU-seconds/sec (90% reduction in connection overhead)

REALITY CHECK: These are cumulative savings across all workers, not end-to-end request latency reduction. Your API won't go from "500ms → 50ms" unless connection overhead was your ONLY bottleneck (rare).

More realistic: "120ms → 60ms" if connection overhead was 50% of request time.

✨ Features

Core Features

• ✅ Connection Pooling - Reuse connections (effective in Swoole/RoadRunner)
• ✅ Auto-Scaling - Dynamically scales from 5 to 400+ connections (long-running processes)
• ✅ Circuit Breaker - Automatic failure detection and graceful degradation
• ✅ SSL/TLS Support - Enterprise security for PostgreSQL and MySQL
• ✅ Auto-Release - Connections automatically returned to pool (prevents leaks)
• ✅ Input Validation - Query size limits (1MB) and param count limits (1000) for memory protection
• ✅ Multi-Database - PostgreSQL, MySQL, SQLite support
• ✅ Framework Agnostic - Works with Laravel, Symfony, or pure PHP
• ✅ PSR-3 Logging - Integrates with Monolog, Laravel Log, Symfony Logger

Enterprise Features

• ✅ Type-Aware Parameter Binding - Automatic boolean/integer/null binding for PostgreSQL/MySQL
• ✅ Query Result Caching - Redis/Memcached integration for SELECT query caching
• ✅ Connection Warmup - Pre-create connections to avoid cold start latency
• ✅ Connection Retry Logic - Exponential backoff (3 retries) on transient failures
• ✅ Monitoring Hooks - New Relic, Datadog, custom metrics integration
• ✅ Transaction Safety - Auto-rollback uncommitted transactions on connection release
• ✅ Slow Query Detection - Automatic logging of queries >100ms (configurable)
• ✅ Prepared Statement Caching - Reuse prepared statements (PostgreSQL optimization)

📦 Installation

composer require senza1dio/database-pool

Requirements:

• PHP 8.0+
• ext-pdo

Recommended:

• ext-redis (for distributed locking at scale)
• ext-pgsql, ext-mysqli, or ext-sqlite3

🚀 Quick Start

Swoole/RoadRunner (Recommended)

<?php
require 'vendor/autoload.php';

use Senza1dio\DatabasePool\Config\PoolConfig;
use Senza1dio\DatabasePool\DatabasePool;

// Configure pool once at application boot
$config = (new PoolConfig())
    ->setHost('localhost')
    ->setPort(5432)
    ->setDatabase('myapp')
    ->setCredentials('postgres', 'secret')
    ->setPoolSize(5, 50);

$pool = new DatabasePool($config);

// Handle requests (pool persists across requests)
while ($request = $server->acceptRequest()) {
    $pdo = $pool->getConnection();
    $stmt = $pdo->prepare('SELECT * FROM users WHERE id = ?');
    $stmt->execute([123]);
    $user = $stmt->fetch();

    // Connection automatically released and returned to pool
}

Pure PHP (CLI Workers/Daemons)

<?php
require 'vendor/autoload.php';

use Senza1dio\DatabasePool\Config\PoolConfig;
use Senza1dio\DatabasePool\DatabasePool;

$config = (new PoolConfig())
    ->setHost('localhost')
    ->setPort(5432)
    ->setDatabase('myapp')
    ->setCredentials('postgres', 'secret')
    ->setPoolSize(5, 50);

$pool = new DatabasePool($config);

// Process queue messages (long-running daemon)
while (true) {
    $message = $queue->pop();

    $pdo = $pool->getConnection();
    $pdo->exec("INSERT INTO processed VALUES (...)");

    // Connection auto-released, reused on next iteration
}

Laravel

<?php
// config/database-pool.php
return [
    'host' => env('DB_HOST', 'localhost'),
    'port' => env('DB_PORT', 5432),
    'database' => env('DB_DATABASE', 'laravel'),
    'username' => env('DB_USERNAME', 'postgres'),
    'password' => env('DB_PASSWORD', ''),
    'minConnections' => 10,
    'maxConnections' => 100,
];

// app/Providers/DatabasePoolServiceProvider.php
use Senza1dio\DatabasePool\Config\PoolConfig;
use Senza1dio\DatabasePool\DatabasePool;
use Senza1dio\DatabasePool\Adapters\Locks\RedisLock;
use Senza1dio\DatabasePool\Adapters\Loggers\Psr3LoggerAdapter;

$this->app->singleton(DatabasePool::class, function ($app) {
    $config = PoolConfig::fromArray(config('database-pool'))
        ->setLock(new RedisLock(Redis::connection()->client()))
        ->setLogger(new Psr3LoggerAdapter(Log::channel('database')));

    return new DatabasePool($config);
});

// Usage in controllers
public function __construct(DatabasePool $pool) {
    $this->pool = $pool;
}

public function show($id) {
    $pdo = $this->pool->getConnection();
    // ... use PDO
}

Symfony

<?php
// config/services.yaml
services:
    Senza1dio\DatabasePool\DatabasePool:
        arguments:
            $config: '@database_pool.config'

    database_pool.config:
        class: Senza1dio\DatabasePool\Config\PoolConfig
        factory: ['Senza1dio\DatabasePool\Config\PoolConfig', 'fromArray']
        arguments:
            - host: '%env(DATABASE_HOST)%'
              port: '%env(int:DATABASE_PORT)%'
              database: '%env(DATABASE_NAME)%'
              username: '%env(DATABASE_USER)%'
              password: '%env(DATABASE_PASSWORD)%'
              minConnections: 10
              maxConnections: 100

// Usage in controllers
public function index(DatabasePool $pool) {
    $pdo = $pool->getConnection();
    // ... use PDO
}

PHP-FPM with Singleton (Built-in Helper)

For PHP-FPM deployments, use the built-in DatabasePoolSingleton:

<?php
use Senza1dio\DatabasePool\Config\PoolConfig;
use Senza1dio\DatabasePool\DatabasePoolSingleton;

$config = (new PoolConfig())
    ->setHost('localhost')
    ->setPort(5432)
    ->setDatabase('myapp')
    ->setCredentials('postgres', 'secret')
    ->setPoolSize(5, 50)
    ->enablePersistentConnections(true);

// Get singleton instance (persists across requests in same worker)
$pool = DatabasePoolSingleton::getInstance($config);
$pdo = $pool->getConnection();

Why this works: Static instance survives across requests within the same PHP-FPM worker.

⚠️ CRITICAL: Config Instance Reuse Required

When using DatabasePoolSingleton, you MUST reuse the same PoolConfig instance:

// ❌ WRONG - Creates new config object each time (will throw LogicException)
$pool = DatabasePoolSingleton::getInstance(PoolConfig::fromArray($config));

// ✅ CORRECT - Reuse same config instance
static $poolConfig = null;
if ($poolConfig === null) {
    $poolConfig = PoolConfig::fromArray($config);
}
$pool = DatabasePoolSingleton::getInstance($poolConfig);

Why: Config identity is checked via spl_object_hash(). Two PoolConfig objects with identical values but different instances are considered different configurations and will throw LogicException.

Alternative: Use DatabasePoolSingleton::reset() to reconfigure, but this closes all connections.

⚠️ Known Limitations

Query Cache (Application-Level, Not Enterprise-Grade)

• Uses fetchAll() internally - not suitable for large datasets (>10k rows)
• No streaming support, breaks memory profile
• Only caches SELECT queries with FETCH_ASSOC
• Reality: This is application-level caching, not database-level optimization
• Best for: Small lookups (<100 rows), frequently-accessed reference data
• Not for: Large reports, streaming queries, cursor-based operations

Prepared Statement Cache (⚠️ Experimental)

• Reuses same PDOStatement object with default fetchMode
• Not safe for scrollable cursors or custom statement attributes
• Not invalidated on reconnect (fragile in edge cases)
• Status: Experimental - use with caution in production
• Best for: Simple repeated queries in stable connections

Locks (Process-Local, Often Unnecessary)

• Semaphore locks prevent race conditions within same PHP process
• Do NOT coordinate between different Swoole/RoadRunner workers
• When useful: Swoole coroutine environments with shared state
• When useless: PHP-FPM (no shared state), single-threaded RoadRunner
• For global coordination, use Redis-based locks (see RedisLock adapter)

Reality: In most deployments, locks add overhead without benefit. They're insurance against edge cases.

SQLite :memory:

• Each connection has separate in-memory database
• Connection pooling loses data between connections
• Use file-based SQLite for pooling benefits

Input Validation (Not True DoS Protection)

• Query size and param count limits protect memory, not pool availability
• Does NOT protect against:
  • Slow queries (use database-level timeouts)
  • Blocking queries (use transaction timeouts)
  • Direct PDO methods (quote(), exec())
  • Multi-statement queries
• Reality: Best-effort protection. Full enforcement only via DatabasePool::executeQuery() API.

📖 Configuration

Fluent Builder API

$config = (new PoolConfig())
    // Database connection
    ->setHost('localhost')
    ->setPort(5432)
    ->setDatabase('myapp')
    ->setCredentials('user', 'pass')
    ->setCharset('utf8')

    // Pool sizing
    ->setPoolSize(10, 100) // Min 10, Max 100

    // SSL/TLS (recommended for production)
    ->enableSsl(
        verify: true,
        required: true,
        ca: '/path/to/ca.pem'
    )

    // Circuit breaker
    ->setCircuitBreaker(
        threshold: 10, // Open after 10 failures
        timeout: 20    // Retry after 20 seconds
    )

    // Query limits (DoS protection)
    ->setQueryLimits(
        maxSize: 1048576,   // 1MB max query
        maxParams: 1000     // 1000 params max
    )

    // Performance tuning
    ->setSlowQueryThreshold(2.0) // Log queries >2s
    ->setIdleTimeout(1500)       // Close idle connections after 25min
    ->enableAutoScaling(true)    // Auto-scale based on load

    // Dependencies (optional)
    ->setLogger($monolog)
    ->setLock($redisLock)

    // Metadata (for monitoring)
    ->setApplicationName('myapp')
    ->setTimezone('Europe/Rome');

From Array (Laravel/Symfony style)

$config = PoolConfig::fromArray([
    'driver' => 'pgsql',
    'host' => 'localhost',
    'port' => 5432,
    'database' => 'myapp',
    'username' => 'postgres',
    'password' => 'secret',
    'min_connections' => 10,
    'max_connections' => 100,
    'ssl' => true,
    'ssl_verify' => true,
    'ssl_ca' => '/path/to/ca.pem',
]);

From DSN

$config = PoolConfig::fromDsn(
    'pgsql:host=localhost;port=5432;dbname=myapp',
    'postgres',
    'secret',
    ['maxConnections' => 100]
);

🚀 Enterprise Features

Type-Aware Parameter Binding

Automatically detects and binds correct PDO types (boolean, integer, null, string). Essential for PostgreSQL/MySQL compatibility.

$pool = new DatabasePool($config);
$pdo = $pool->getConnection();

// Type-aware binding (no manual PDO::PARAM_* needed)
$stmt = $pool->executeQuery($pdo, '
    INSERT INTO users (is_active, age, name, bio)
    VALUES (:is_active, :age, :name, :bio)
', [
    'is_active' => true,    // Auto-detected as PARAM_BOOL
    'age' => 25,            // Auto-detected as PARAM_INT
    'name' => 'John',       // Auto-detected as PARAM_STR
    'bio' => null,          // Auto-detected as PARAM_NULL
]);

Query Result Caching

Cache SELECT query results in Redis/Memcached for massive performance gains.

// Setup Redis cache
$redis = new \Redis();
$redis->connect('127.0.0.1', 6379);
$pool->setQueryCache($redis);

// Execute cached query
$stmt = $pool->executeQuery($pdo, 'SELECT * FROM products WHERE category_id = ?', [123], [
    'cache' => true,        // Enable caching
    'cache_ttl' => 300,     // Cache for 5 minutes
]);

// Second request = instant (Redis cache hit)

Connection Warmup

Pre-create connections on application boot to eliminate cold start latency.

$pool = new DatabasePool($config);

// Warmup 10 connections (recommended after deployment)
$created = $pool->warmup(10);

// First user request = instant (connections already created)

Monitoring Hooks (New Relic / Datadog)

Integrate with external monitoring systems for real-time metrics.

// New Relic integration
$pool->addMonitoringHook(function($metrics) {
    if (extension_loaded('newrelic')) {
        newrelic_custom_metric('Database/QueryTime', $metrics['duration_ms']);
        newrelic_custom_metric('Database/SlowQueries', $metrics['slow_queries']);
    }
});

// Datadog integration
$pool->addMonitoringHook(function($metrics) use ($statsd) {
    $statsd->timing('database.query.duration', $metrics['duration_ms']);
    $statsd->increment('database.queries.total');
    $statsd->gauge('database.pool.active', $metrics['active_connections']);
});

// Custom metrics
$pool->addMonitoringHook(function($metrics) {
    file_put_contents('/var/log/db-metrics.log', json_encode($metrics) . PHP_EOL, FILE_APPEND);
});

Connection Retry Logic

Automatic retry with exponential backoff on transient failures (network hiccups, temporary DB overload).

// Configured automatically (3 retries with exponential backoff)
// Retry 1: 100ms delay
// Retry 2: 200ms delay
// Retry 3: 400ms delay

$pool = new DatabasePool($config);
$pdo = $pool->getConnection(); // Auto-retries on failure

// Check metrics
$metrics = $pool->getMetrics();
echo "Connection retries: {$metrics['connection_retries']}";

Transaction Safety

Automatically rolls back uncommitted transactions when connections are released. Prevents data corruption and state leakage.

$pdo = $pool->getConnection();

$pdo->beginTransaction();
$pdo->exec('UPDATE accounts SET balance = balance - 100 WHERE id = 1');

// Developer forgets to commit/rollback
unset($pdo); // Connection released

// AUTOMATIC ROLLBACK HAPPENS HERE
// No data corruption! Transaction rolled back safely.

$metrics = $pool->getMetrics();
echo "Auto-rollbacks: {$metrics['transaction_rollbacks']}";

🔒 Security Features

SSL/TLS Enforcement

$config = (new PoolConfig())
    ->enableSsl(
        verify: true,      // Verify server certificate
        required: true,    // Fail if SSL not available
        ca: '/path/to/ca.pem'
    )
    ->setSslCertificate(
        '/path/to/client.crt',
        '/path/to/client.key'
    );

DoS Protection

$config = (new PoolConfig())
    ->setQueryLimits(
        maxSize: 1048576,   // 1MB max query (prevents memory exhaustion)
        maxParams: 1000     // Max 1000 params (prevents parameter bombing)
    );

Circuit Breaker

Automatically opens after threshold failures, preventing cascade failures:

try {
    $pdo = $pool->getConnection();
} catch (CircuitBreakerOpenException $e) {
    // Circuit breaker is open
    // Retry after $e->getTimeout() seconds
    sleep(20);
    $pdo = $pool->getConnection();
}

🎯 Performance

Connection Pooling Benefits

Without pooling:

• 10,000 requests = 10,000 new connections
• Connection time: 10-50ms each
• Total overhead: 100-500 seconds

With pooling:

• 10,000 requests = 50 pooled connections (reused)
• Connection time: 10-50ms × 50 = 0.5-2.5 seconds
• Total overhead: 0.5-2.5 seconds (100-200x faster!)

Auto-Scaling

Pool automatically scales based on demand:

Load Low  (0-20%)  → 10 connections
Load Med  (20-50%) → 30 connections  (1.5x scale)
Load High (50-80%) → 50 connections  (1.5x scale)
Load Peak (80%+)   → 100 connections (2x scale)

Benchmarks

Hardware: 4-core CPU, 16GB RAM, PostgreSQL 17

🔧 Advanced Usage

Distributed Locking (Redis)

use Senza1dio\DatabasePool\Adapters\Locks\RedisLock;

$redis = new Redis();
$redis->connect('localhost', 6379);

$config = (new PoolConfig())
    // ... other config
    ->setLock(new RedisLock($redis, 'myapp:pool:'));

$pool = new DatabasePool($config);

PSR-3 Logging

use Senza1dio\DatabasePool\Adapters\Loggers\Psr3LoggerAdapter;
use Monolog\Logger;
use Monolog\Handler\StreamHandler;

$logger = new Logger('database');
$logger->pushHandler(new StreamHandler('php://stdout'));

$config = (new PoolConfig())
    // ... other config
    ->setLogger(new Psr3LoggerAdapter($logger));

$pool = new DatabasePool($config);
// Slow queries, errors, circuit breaker events logged automatically

Metrics & Monitoring

$stats = $pool->getStats();

/*
[
    'total_connections' => 50,
    'active_connections' => 20,
    'idle_connections' => 30,
    'total_queries' => 10000,
    'slow_queries' => 5,
    'circuit_breaker_state' => 'closed',
    'pool_hits' => 9950,      // Reused connections
    'pool_misses' => 50,      // New connections created
]
*/

🆚 Comparison

🧪 Test Results

All 32 tests passed - See TESTING_RESULTS.md for complete report.

Test Suite Overview

Performance Benchmarks

E-commerce Scenario Results

✅ Successful checkout - Inventory check → payment → order (all atomic) ✅ Failed checkout rollback - Payment fails → complete ROLLBACK (no data corruption) ✅ Concurrent checkout prevention - SELECT FOR UPDATE prevents overselling ✅ Multi-item cart - 3 products, $3999.96 total, all steps atomic

Read full report: TESTING_RESULTS.md

🤝 Contributing

Contributions welcome! Please:

1. Fork the repository
2. Create a feature branch
3. Add tests for new features
4. Run composer check (PHPStan + Tests + CS-Fixer)
5. Submit a pull request

📄 License

MIT License. See LICENSE file.

💬 Support

• Issues: GitHub Issues
• Discussions: GitHub Discussions
• Email: senza1dio@gmail.com

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