#16 Add Symfony Cache as an alternative SSE adapter

Introduced a new adapter leveraging Symfony Cache for handling SSE messages as an alternative to Redis. Updated configuration, README, and tests to support the `cache` adapter, providing more flexibility for environments without Redis. Implemented comprehensive unit tests for the new CachePoolAdapter.

Author: klapaudius

README.md

@@ -7,10 +7,10 @@
 <p align="center">
 <a href="https://github.com/klapaudius/symfony-mcp-server/actions"><img src="https://github.com/klapaudius/symfony-mcp-server/actions/workflows/tests.yml/badge.svg" alt="Build Status"></a>
 <a href="https://codecov.io/gh/klapaudius/symfony-mcp-server" >  <img src="https://codecov.io/gh/klapaudius/symfony-mcp-server/graph/badge.svg?token=5FXOJVXPZ1" alt="Coverage"/></a>
+<a href="https://packagist.org/packages/klapaudius/symfony-mcp-server"><img src="https://img.shields.io/packagist/l/klapaudius/symfony-mcp-server" alt="License"></a>
 
-[//]: # (<a href="https://packagist.org/packages/klapaudius/symfony-mcp-server"><img src="https://img.shields.io/packagist/dt/klapaudius/symfony-mcp-server" alt="Total Downloads"></a>)
 [//]: # (<a href="https://packagist.org/packages/klapaudius/symfony-mcp-server"><img src="https://img.shields.io/packagist/v/klapaudius/symfony-mcp-server" alt="Latest Stable Version"></a>)
-[//]: # (<a href="https://packagist.org/packages/klapaudius/symfony-mcp-server"><img src="https://img.shields.io/packagist/l/klapaudius/symfony-mcp-server" alt="License"></a>)
+[//]: # (<a href="https://packagist.org/packages/klapaudius/symfony-mcp-server"><img src="https://img.shields.io/packagist/dt/klapaudius/symfony-mcp-server" alt="Total Downloads"></a>)
 </p>
 
 ## Overview
@@ -41,7 +41,7 @@ Key benefits:
 
 - Real-time communication support through Server-Sent Events (SSE) integration specified in the MCP 2024-11-05 version (Streamable HTTP from 2025-03-26 version is planned)
 - Implementation of tools and resources compliant with Model Context Protocol specifications
-- Adapter-based design architecture with Pub/Sub messaging pattern (starting with Redis, more adapters planned)
+- Adapter-based design architecture with Pub/Sub messaging pattern
 
 ## Requirements
 
@@ -63,11 +63,10 @@ Key benefits:
             enabled: true  # Read the warning section in the default configuration file before disable it
             interval: 30
         server_provider: 'sse'
-        sse_adapter: 'redis'
+        sse_adapter: 'cache'
         adapters:
-            redis:
+            cache:
                 prefix: 'mcp_sse_'
-                host: 'localhost'  # Change it as needed
                 ttl: 100
         tools:
             - KLP\KlpMcpServer\Services\ToolService\Examples\HelloWorldTool
@@ -138,7 +137,7 @@ php bin/console mcp:test-tool MyCustomTool
 php bin/console mcp:test-tool --list
 
 # Test with specific JSON input
-php bin/console mcp:test-tool MyCustomTool --input='{"param":"value"}'
+php bin/console mcp:test-tool MyCustomTool --input='{"param1":"value"}'
 ```
 
 This helps you rapidly develop and debug tools by:
@@ -177,7 +176,7 @@ The package implements a publish/subscribe (pub/sub) messaging pattern through i
 
 1. **Publisher (Server)**: When clients send requests to the `/messages` endpoint, the server processes these requests and publishes responses through the configured adapter.
 
-2. **Message Broker (Adapter)**: The adapter (e.g., Redis) maintains message queues for each client, identified by unique client IDs. This provides a reliable asynchronous communication layer.
+2. **Message Broker (Adapter)**: The adapter maintains message queues for each client, identified by unique client IDs. This provides a reliable asynchronous communication layer.
 
 3. **Subscriber (SSE Connection)**: Long-lived SSE connections subscribe to messages for their respective clients and deliver them in real-time.
 
@@ -188,9 +187,9 @@ This architecture enables:
 - Efficient handling of multiple concurrent client connections
 - Potential for distributed server deployments
 
-### Redis Adapter Configuration
+### Redis Adapter Configuration (Optional)
 
-The default Redis adapter can be configured as follows:
+A Redis adapter can be configured as follows:
 
 
 ```yaml
@@ -219,6 +218,7 @@ Basic implementation of the Model Context Protocol (MCP) server using Server-Sen
 - **Core Features:**
   - **Refactoring:** Refactor `TestMcpToolCommand` to reduce technical debt and improve code maintainability.
   - **Testing Enhancements:** Enhance test coverage to achieve an acceptable and robust ratio, ensuring reliability and stability.
+  - **New Adapter**: Symfony Cache adpater for Pub/Sub messaging pattern
 - **Documentation:**
   - **Examples and Use Cases:** Include additional examples and use cases to illustrate practical applications and best practices.
 

composer.json

@@ -8,8 +8,8 @@
     "require": {
         "php": "^8.2",
         "ext-json": "*",
-        "ext-redis": "*",
         "psr/log": "^3.0",
+        "symfony/cache": "^7.2",
         "symfony/config": "~7.0",
         "symfony/console": "~7.0",
         "symfony/dependency-injection": "~7.0",
@@ -24,6 +24,7 @@
         "phpstan/phpstan-phpunit": "^1.3||^2.0"
     },
     "suggest": {
+        "ext-redis": "To enable redis SSE Adapter",
         "klapaudius/oauth-server-bundle": "For a complete OAuth2 Authentication mechanism"
     },
     "autoload": {

src/DependencyInjection/Configuration.php

@@ -11,7 +11,7 @@ public function getConfigTreeBuilder(): TreeBuilder
     {
         $treeBuilder = new TreeBuilder('klp_mcp_server');
         $rootNode = $treeBuilder->getRootNode();
-        $supportedAdapters = ['redis'];
+        $supportedAdapters = ['cache', 'redis'];
         $supportedAdaptersServices = array_map(function ($item) {
             return $item;
         }, $supportedAdapters);
@@ -67,7 +67,7 @@ public function getConfigTreeBuilder(): TreeBuilder
 
                 // SSE Adapter
             ->scalarNode('sse_adapter')
-            ->defaultValue('redis')
+            ->defaultValue('cache')
             ->cannotBeEmpty()
             ->validate()
             ->ifNotInArray($supportedAdaptersServices)
@@ -77,7 +77,7 @@ public function getConfigTreeBuilder(): TreeBuilder
 
                 // Adapters for SSE
             ->arrayNode('adapters')
-            ->useAttributeAsKey('name') // Allows keys like "in_memory" and "redis"
+            ->useAttributeAsKey('name') // Allows keys like "cache" and "redis"
             ->arrayPrototype()
             ->children()
             ->scalarNode('prefix')

src/DependencyInjection/KlpMcpServerExtension.php

@@ -22,10 +22,12 @@ public function load(array $configs, ContainerBuilder $container): void
         $container->setParameter('klp_mcp_server.ping.enabled', $config['ping']['enabled']);
         $container->setParameter('klp_mcp_server.ping.interval', $config['ping']['interval']);
         $container->setParameter('klp_mcp_server.provider', 'klp_mcp_server.provider.'.$config['server_provider']);
-        $container->setParameter('klp_mcp_server.adapter', 'klp_mcp_server.adapter.'.$config['sse_adapter']);
+        $container->setParameter('klp_mcp_server.sse_adapter', $config['sse_adapter']);
         $container->setParameter('klp_mcp_server.adapters.redis.prefix', $config['adapters']['redis']['prefix'] ?? 'mcp_sse');
         $container->setParameter('klp_mcp_server.adapters.redis.host', $config['adapters']['redis']['host'] ?? 'default');
         $container->setParameter('klp_mcp_server.adapters.redis.ttl', $config['adapters']['redis']['ttl'] ?? 100);
+        $container->setParameter('klp_mcp_server.adapters.cache.prefix', $config['adapters']['cache']['prefix'] ?? 'mcp_sse');
+        $container->setParameter('klp_mcp_server.adapters.cache.ttl', $config['adapters']['cache']['ttl'] ?? 100);
         $container->setParameter('klp_mcp_server.tools', $config['tools']);
     }
 }

src/Resources/config/packages/klp_mcp_server.yaml

@@ -49,8 +49,13 @@ klp_mcp_server:
     # The Redis adapter uses Redis lists as message queues, with each client
     # having its own queue identified by a unique client ID. This enables
     # efficient and scalable real-time communication in distributed environments
-    sse_adapter: 'redis'
+    # If a Redis server is not an option, the 'cache' adapter can be utilized
+    # as an alternative
+    sse_adapter: 'redis'        # Or 'cache'
     adapters:
+        cache:
+            prefix: 'mcp_sse_'  # Prefix for cache item keys
+            ttl: 100            # Message TTL in seconds
         redis:
             prefix: 'mcp_sse_'  # Prefix for Redis keys
             host: 'localhost'   # Change it as needed

src/Resources/config/services.xml

@@ -27,18 +27,17 @@
             <tag name="console.command" />
         </service>
 
-        <service id="klp_mcp_server.adapter.default" alias="klp_mcp_server.adapter.redis" />
-        <service id="klp_mcp_server.adapter.redis" class="KLP\KlpMcpServer\Transports\SseAdapters\RedisAdapter">
-            <argument type="collection">
-                <argument key="prefix">%klp_mcp_server.adapters.redis.prefix%</argument>
-                <argument key="host">%klp_mcp_server.adapters.redis.host%</argument>
-                <argument key="ttl">%klp_mcp_server.adapters.redis.ttl%</argument>
-            </argument>
-            <argument type="service" id="logger" on-invalid="null" />
+        <service id="klp_mcp_server.adapter.factory" class="KLP\KlpMcpServer\Transports\SseAdapters\SseAdapterFactory">
+            <argument type="service" id="service_container" />
         </service>
+
+        <service id="klp_mcp_server.adapter" class="KLP\KlpMcpServer\Transports\SseAdapters\SseAdapterInterface">
+            <factory service="klp_mcp_server.adapter.factory" method="create" />
+        </service>
+
         <service id="klp_mcp_server.transport.sse" class="KLP\KlpMcpServer\Transports\SseTransport">
             <argument type="string">%klp_mcp_server.default_path%</argument>
-            <argument type="service" id="klp_mcp_server.adapter.redis" on-invalid="null" />
+            <argument type="service" id="klp_mcp_server.adapter" on-invalid="null" />
             <argument type="service" id="logger" on-invalid="null" />
             <argument type="binary">%klp_mcp_server.ping.enabled%</argument>
             <argument type="string">%klp_mcp_server.ping.interval%</argument>

src/Transports/SseAdapters/CachePoolAdapter.php

@@ -0,0 +1,137 @@
+<?php
+
+namespace KLP\KlpMcpServer\Transports\SseAdapters;
+
+use Psr\Cache\CacheItemPoolInterface;
+use Psr\Cache\InvalidArgumentException;
+use Psr\Log\LoggerInterface;
+
+class CachePoolAdapter implements SseAdapterInterface
+{
+    private const DEFAULT_PREFIX = 'mcp_sse_';
+
+    private const DEFAULT_MESSAGE_TTL = 100;
+
+    /**
+     * Key prefix for SSE messages
+     */
+    private string $keyPrefix;
+
+    /**
+     * Message expiration time in seconds
+     */
+    private int $messageTtl;
+
+    public function __construct(
+        private readonly array $config,
+        private readonly CacheItemPoolInterface $cache,
+        private readonly ?LoggerInterface $logger
+    ) {
+        $this->keyPrefix = $this->config['prefix'] ?? self::DEFAULT_PREFIX;
+        $this->messageTtl = (int) ($this->config['ttl'] ?? self::DEFAULT_MESSAGE_TTL);
+    }
+
+    /**
+     * Get the Redis key for a client's message queue
+     *
+     * @param  string  $clientId  The client ID
+     * @return string The Redis key
+     */
+    private function generateQueueKey(string $clientId): string
+    {
+        return "$this->keyPrefix|client|$clientId";
+    }
+    /**
+     * @inheritDoc
+     */
+    public function pushMessage(string $clientId, string $message): void
+    {
+        try {
+            $cacheItem = $this->cache->getItem($this->generateQueueKey($clientId));
+
+            $messages = $cacheItem->isHit() ? $cacheItem->get() : [] ;
+            $messages[] = $message;
+            $cacheItem->set($messages);
+            $cacheItem->expiresAfter($this->messageTtl);
+            $this->cache->save($cacheItem);
+        } catch (InvalidArgumentException $e) {
+            $this->logger?->error('Failed to add message to cache: '.$e->getMessage());
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function removeAllMessages(string $clientId): void
+    {
+        try {
+            $this->cache->deleteItem($this->generateQueueKey($clientId));
+        } catch (InvalidArgumentException $e) {
+            $this->logger?->error('Failed to remove messages from cache: '.$e->getMessage());
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function receiveMessages(string $clientId): array
+    {
+        return $this->cache->getItem($this->generateQueueKey($clientId))->get() ?? [];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function popMessage(string $clientId): ?string
+    {
+        try {
+            $cacheItem = $this->cache->getItem($this->generateQueueKey($clientId));
+            $messages = $cacheItem->get() ?? [];
+            $message = array_shift($messages);
+            $cacheItem->set($messages);
+            $cacheItem->expiresAfter($this->messageTtl);
+            $this->cache->save($cacheItem);
+
+            return $message;
+        } catch (InvalidArgumentException $e) {
+            $this->logger?->error('Failed to pop message from cache: '.$e->getMessage());
+
+            return null;
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasMessages(string $clientId): bool
+    {
+        return $this->cache->getItem($this->generateQueueKey($clientId))->isHit();
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getMessageCount(string $clientId): int
+    {
+        return count($this->cache->getItem($this->generateQueueKey($clientId))->get() ?? []);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function storeLastPongResponseTimestamp(string $clientId, ?int $timestamp = null): void
+    {
+        $cacheItem = $this->cache->getItem($this->generateQueueKey($clientId).'|last_pong');
+        $cacheItem->set($timestamp ?? time());
+        $cacheItem->expiresAfter($this->messageTtl);
+        $this->cache->save($cacheItem);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getLastPongResponseTimestamp(string $clientId): ?int
+    {
+        return $this->cache->getItem($this->generateQueueKey($clientId).'|last_pong')->get();
+    }
+}

src/Transports/SseAdapters/SseAdapterFactory.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace KLP\KlpMcpServer\Transports\SseAdapters;
+
+use Psr\Log\LoggerInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
+
+class SseAdapterFactory
+{
+    private ?\Redis $mockRedis = null;
+
+    public function __construct(
+        private readonly ContainerInterface $container,
+        private readonly ?LoggerInterface $logger = null
+    ) {}
+
+    /**
+     * Creates and retrieves an instance of SseAdapterInterface.
+     *
+     * @return SseAdapterInterface Returns an instance of SseAdapterInterface if the retrieved adapter is valid.
+     * @throws SseAdapterException Throws an exception if the retrieved adapter is not a valid instance of SseAdapterInterface.
+     */
+    public function create(): SseAdapterInterface
+    {
+        return match ($this->container->getParameter('klp_mcp_server.sse_adapter')) {
+            'redis' => $this->createRedisAdapter(),
+            'cache' => $this->createCachePoolAdapter(),
+            default => throw new SseAdapterException('Invalid adapter')
+        };
+    }
+
+    private function createCachePoolAdapter(): CachePoolAdapter
+    {
+        return new CachePoolAdapter([
+                'prefix' => $this->container->getParameter('klp_mcp_server.adapters.cache.prefix'),
+                'ttl' => $this->container->getParameter('klp_mcp_server.adapters.cache.ttl'),
+            ],
+            $this->container->get('cache.app'),
+            $this->logger
+        );
+    }
+
+    private function createRedisAdapter(): RedisAdapter
+    {
+        return new RedisAdapter(
+            [
+                'prefix' => $this->container->getParameter('klp_mcp_server.adapters.redis.prefix'),
+                'host' => $this->container->getParameter('klp_mcp_server.adapters.redis.host'),
+                'ttl' => $this->container->getParameter('klp_mcp_server.adapters.redis.ttl'),
+            ],
+            $this->logger,
+            $this->mockRedis
+        );
+    }
+}