KurrentDB PHP Client

A modern PHP client library for KurrentDB (formerly EventStoreDB) HTTP API, designed for event sourcing applications.

Note: This library uses the HTTP API. For TCP integration, see prooph/event-store-client.

Features

• ✅ Support for KurrentDB HTTP API
• ✅ Event stream management (read, write, delete)
• ✅ Optimistic concurrency control
• ✅ Stream iteration (forward and backward)
• ✅ Batch operations for performance
• ✅ Built-in HTTP caching support
• ✅ PSR-7 and PSR-18 compliant
• ✅ Type-safe with PHP 8.4 features
• ✅ Comprehensive error handling

Architecture

The library follows a clean architecture with a facade pattern that promotes separation of concerns and follows SOLID principles:

Facade Pattern

EventStore acts as a facade that delegates operations to specialized services:

• StreamReader - Handles all stream reading operations
• StreamWriter - Manages stream writing and deletion operations
• StreamIteratorFactory - Creates stream iterators for navigation

Factory Pattern

EventStoreFactory provides the recommended way to instantiate EventStore with proper dependency injection and connection validation:

// Simple creation with default dependencies
$eventStore = EventStoreFactory::create($uri);

// With custom HTTP client
$eventStore = EventStoreFactory::createWithHttpClient($uri, $httpClient);

// With all custom dependencies
$eventStore = EventStoreFactory::createWithDependencies(
    $uri,
    $httpClient,
    $streamReader,
    $streamWriter,
    $streamIteratorFactory
);

Benefits

• Testability - Each service can be mocked independently
• Separation of Concerns - Clear boundaries between reading, writing, and iteration
• SOLID Principles - Interface segregation and dependency inversion
• Maintainability - Easier to extend and modify individual components
• Type Safety - Strong typing throughout the service layer

Requirements

• PHP 8.4 or higher
• KurrentDB server (HTTP API enabled)

Installation

Via Composer

composer require friendsofouro/kurrentdb-core

Via Metapackage (Recommended)

For the complete package with additional integrations:

composer require friendsofouro/kurrentdb

Local Development

git clone [email protected]:FriendsOfOuro/kurrentdb-php-core.git
cd kurrentdb-php-core

# Start the environment
make up

# Install dependencies
make install

# Run tests to verify setup
make test

Quick Start

Basic Setup

use KurrentDB\EventStoreFactory;

// Create EventStore using factory (recommended)
$eventStore = EventStoreFactory::create('http://admin:[email protected]:2113');

// Or with custom HTTP client
use KurrentDB\Http\GuzzleHttpClient;

$httpClient = new GuzzleHttpClient();
$eventStore = EventStoreFactory::createWithHttpClient(
    'http://admin:[email protected]:2113',
    $httpClient
);

Writing Events

use KurrentDB\WritableEvent;
use KurrentDB\WritableEventCollection;

// Write a single event
$event = WritableEvent::newInstance(
    'UserRegistered',
    ['userId' => '123', 'email' => '[email protected]'],
    ['timestamp' => time()] // optional metadata
);

$version = $eventStore->writeToStream('user-123', $event);

// Write multiple events atomically
$events = new WritableEventCollection([
    WritableEvent::newInstance('OrderPlaced', ['orderId' => '456']),
    WritableEvent::newInstance('PaymentProcessed', ['amount' => 99.99])
]);

$eventStore->writeToStream('order-456', $events);

Reading Events

use KurrentDB\StreamFeed\EntryEmbedMode;

$feed = $eventStore->openStreamFeed('user-123');

// Get entries and read events
foreach ($feed->getEntries() as $entry) {
    $event = $eventStore->readEvent($entry->getEventUrl());
    echo sprintf("Event: %s, Version: %d\n", 
        $event->getType(), 
        $event->getVersion()
    );
}

// Read with embedded event data for better performance
$feed = $eventStore->openStreamFeed('user-123', EntryEmbedMode::BODY);

Stream Navigation

use KurrentDB\StreamFeed\LinkRelation;

// Navigate through pages
$feed = $eventStore->openStreamFeed('large-stream');
$nextPage = $eventStore->navigateStreamFeed($feed, LinkRelation::NEXT);

// Use iterators for convenient traversal
$iterator = $eventStore->forwardStreamFeedIterator('user-123');
foreach ($iterator as $entryWithEvent) {
    $event = $entryWithEvent->getEvent();
    // Process event...
}

// Backward iteration
$reverseIterator = $eventStore->backwardStreamFeedIterator('user-123');

Optimistic Concurrency Control

use KurrentDB\ExpectedVersion;

// Write with expected version
$eventStore->writeToStream(
    'user-123', 
    $event, 
    5
);

// Special version expectations
$eventStore->writeToStream('new-stream', $event, ExpectedVersion::NO_STREAM);
$eventStore->writeToStream('any-stream', $event, ExpectedVersion::ANY);

Stream Management

use KurrentDB\StreamDeletion;

// Soft delete (can be recreated)
$eventStore->deleteStream('old-stream', StreamDeletion::SOFT);

// Hard delete (permanent, will be 410 Gone)
$eventStore->deleteStream('obsolete-stream', StreamDeletion::HARD);

Advanced Usage

HTTP Caching

Improve performance with built-in caching:

// Filesystem cache
$httpClient = GuzzleHttpClient::withFilesystemCache('/tmp/kurrentdb-cache');
$eventStore = EventStoreFactory::createWithHttpClient($url, $httpClient);

// APCu cache (in-memory)
$httpClient = GuzzleHttpClient::withApcuCache();
$eventStore = EventStoreFactory::createWithHttpClient($url, $httpClient);

// Custom PSR-6 cache
use Symfony\Component\Cache\Adapter\RedisAdapter;
$cacheAdapter = new RedisAdapter($redisClient);
$httpClient = GuzzleHttpClient::withPsr6Cache($cacheAdapter);
$eventStore = EventStoreFactory::createWithHttpClient($url, $httpClient);

Custom Service Dependencies

For advanced use cases, you can provide custom implementations of the core services:

use KurrentDB\EventStoreFactory;
use KurrentDB\Service\StreamReaderInterface;
use KurrentDB\Service\StreamWriterInterface;
use KurrentDB\Service\StreamIteratorFactoryInterface;

// Create custom service implementations
$customStreamReader = new MyCustomStreamReader($httpClient);
$customStreamWriter = new MyCustomStreamWriter($httpClient);
$customIteratorFactory = new MyCustomIteratorFactory($streamReader);

// Create EventStore with custom dependencies
$eventStore = EventStoreFactory::createWithDependencies(
    $uri,
    $httpClient,
    $customStreamReader,
    $customStreamWriter,
    $customIteratorFactory
);

Batch Operations

Read multiple events efficiently:

// Collect event URLs
$eventUrls = [];
foreach ($feed->getEntries() as $entry) {
    $eventUrls[] = $entry->getEventUrl();
}

// Batch read
$events = $eventStore->readEventBatch($eventUrls);
foreach ($events as $event) {
    // Process events...
}

Error Handling

use KurrentDB\Exception\StreamNotFoundException;
use KurrentDB\Exception\WrongExpectedVersionException;
use KurrentDB\Exception\StreamGoneException;

try {
    $eventStore->writeToStream('user-123', $event, 10);
} catch (WrongExpectedVersionException $e) {
    // Handle version conflict
    echo "Version mismatch: " . $e->getMessage();
} catch (StreamNotFoundException $e) {
    // Stream doesn't exist
    echo "Stream not found: " . $e->getMessage();
} catch (StreamGoneException $e) {
    // Stream was permanently deleted (hard delete)
    echo "Stream gone: " . $e->getMessage();
}

Custom HTTP Client

You can provide your own HTTP client implementing HttpClientInterface:

use KurrentDB\Http\HttpClientInterface;

class MyCustomHttpClient implements HttpClientInterface
{
    public function send(RequestInterface $request): ResponseInterface
    {
        // Custom implementation
    }
    
    public function sendBatch(RequestInterface ...$requests): \Iterator
    {
        // Batch implementation
    }
}

$eventStore = EventStoreFactory::createWithHttpClient($url, new MyCustomHttpClient());

Development Setup

Quick Start with Make

# Start KurrentDB and build PHP container
make up

# Install dependencies
make install

# Run tests
make test

# Run tests with coverage
make test-coverage

# Check code style
make cs-fixer-ci

# Fix code style
make cs-fixer

# Run static analysis
make phpstan

# Run benchmarks
make benchmark

# View logs
make logs

# Stop containers
make down

Testing

The project uses PHPUnit for testing:

# Run all tests
make test

# Run with coverage report
make test-coverage

# Run specific test file
docker compose exec php bin/phpunit tests/Tests/EventStoreTest.php

API Reference

Main Classes

• EventStore - Main facade class for all operations
• EventStoreFactory - Factory for creating EventStore instances with proper dependencies
• WritableEvent - Represents an event to be written
• WritableEventCollection - Collection of events for atomic writes
• StreamFeed - Paginated view of a stream
• Event - Represents a read event with version and metadata

Service Classes

• StreamReader - Handles stream reading operations
• StreamWriter - Manages stream writing and deletion
• StreamIteratorFactory - Creates stream iterators for navigation

Enums

• StreamDeletion - SOFT or HARD deletion modes
• EntryEmbedMode - NONE, RICH, or BODY embed modes
• LinkRelation - FIRST, LAST, NEXT, PREVIOUS, etc.

Interfaces

• EventStoreInterface - Main service interface
• HttpClientInterface - HTTP client abstraction
• WritableToStream - Objects that can be written to streams

Docker Environment

The project includes a complete Docker setup with:

• KurrentDB (latest) with projections enabled and health checks
• PHP container with all required extensions and dependencies
• Persistent volumes for KurrentDB data and logs
• Automatic service dependency management

The KurrentDB instance is configured with:

• HTTP API on port 2113
• Default credentials: admin:changeit
• All projections enabled
• AtomPub over HTTP enabled

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Before submitting:

# Run tests
make test

# Check code style
make cs-fixer-ci

# Run static analysis
make phpstan

# Check source dependencies
make check-src-deps

Dependency Validation

The project includes dependency validation using composer-require-checker to ensure all used dependencies are properly declared in composer.json:

# Check for missing dependencies in source code
make check-src-deps

License

This project is licensed under the MIT License - see the LICENSE file for details.

Disclaimer

This project is not endorsed by Event Store LLP nor Kurrent Inc.

Support

• GitHub Issues
• Documentation
• KurrentDB Community