[Server] Add missing handler for resource subscribe/unsubscribe handlers

.github/workflows/pipeline.yaml

@@ -100,7 +100,7 @@ jobs:
           passedTests=$(echo "$OUTPUT" | sed -nE 's/.*Total: ([0-9]+) passed.*/\1/p')
           passedTests=${passedTests:-0}
           
-          REQUIRED_TESTS_TO_PASS=22
+          REQUIRED_TESTS_TO_PASS=25
           echo "Required tests to pass: $REQUIRED_TESTS_TO_PASS"
           [ "$passedTests" -ge "$REQUIRED_TESTS_TO_PASS" ] || exit $exit_code
 

src/Capability/Registry.php

@@ -25,14 +25,20 @@
 use Mcp\Exception\PromptNotFoundException;
 use Mcp\Exception\ResourceNotFoundException;
 use Mcp\Exception\ToolNotFoundException;
+use Mcp\Schema\Notification\ResourceUpdatedNotification;
 use Mcp\Schema\Page;
 use Mcp\Schema\Prompt;
 use Mcp\Schema\Resource;
 use Mcp\Schema\ResourceTemplate;
 use Mcp\Schema\Tool;
+use Mcp\Server\Protocol;
+use Mcp\Server\Session\SessionFactoryInterface;
+use Mcp\Server\Session\SessionInterface;
+use Mcp\Server\Session\SessionStoreInterface;
 use Psr\EventDispatcher\EventDispatcherInterface;
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
+use Psr\SimpleCache\InvalidArgumentException;
 
 /**
  * Registry implementation that manages MCP element registration and access.
@@ -64,6 +70,8 @@ final class Registry implements RegistryInterface
     public function __construct(
         private readonly ?EventDispatcherInterface $eventDispatcher = null,
         private readonly LoggerInterface $logger = new NullLogger(),
+        private readonly ?SessionStoreInterface $sessionStore = null,
+        private readonly ?SessionFactoryInterface $sessionFactory = null,
         private readonly NameValidator $nameValidator = new NameValidator(),
     ) {
     }
@@ -391,6 +399,64 @@ public function setDiscoveryState(DiscoveryState $state): void
         }
     }
 
+    /**
+     * @throws InvalidArgumentException
+     */
+    public function subscribe(SessionInterface $session, string $uri): void
+    {
+        $subscriptions = $session->get('resource_subscriptions', []);
+        $subscriptions[$uri] = true;
+        $session->set('resource_subscriptions', $subscriptions);
+        $session->save();
+    }
+
+    /**
+     * @throws InvalidArgumentException
+     */
+    public function unsubscribe(SessionInterface $session, string $uri): void
+    {
+        $subscriptions = $session->get('resource_subscriptions', []);
+        unset($subscriptions[$uri]);
+        $session->set('resource_subscriptions', $subscriptions);
+        $session->save();
+    }
+
+    public function notifyResourceChanged(Protocol $protocol, string $uri): void
+    {
+        if (!$this->sessionStore || !$this->sessionFactory) {
+            $this->logger->warning('Cannot send resource notifications: session store or factory not configured.');
+
+            return;
+        }
+
+        foreach ($this->sessionStore->getAllSessionIds() as $sessionId) {
+            try {
+                $sessionData = $this->sessionStore->read($sessionId);
+                if (!$sessionData) {
+                    continue;
+                }
+
+                $sessionArray = json_decode($sessionData, true);
+                if (!\is_array($sessionArray)) {
+                    continue;
+                }
+
+                if (!isset($sessionArray['resource_subscriptions'][$uri])) {
+                    continue;
+                }
+
+                $session = $this->sessionFactory->createWithId($sessionId, $this->sessionStore);
+                $protocol->sendNotification(new ResourceUpdatedNotification($uri), $session);
+            } catch (\Throwable $e) {
+                $this->logger->error('Error sending resource notification to session', [
+                    'session_id' => $sessionId->toRfc4122(),
+                    'uri' => $uri,
+                    'exception' => $e,
+                ]);
+            }
+        }
+    }
+
     /**
      * Calculate next cursor for pagination.
      *

src/Capability/RegistryInterface.php

@@ -25,6 +25,8 @@
 use Mcp\Schema\Resource;
 use Mcp\Schema\ResourceTemplate;
 use Mcp\Schema\Tool;
+use Mcp\Server\Protocol;
+use Mcp\Server\Session\SessionInterface;
 
 /**
  * @phpstan-import-type Handler from ElementReference
@@ -157,4 +159,20 @@ public function getPrompts(?int $limit = null, ?string $cursor = null): Page;
      * @throws PromptNotFoundException
      */
     public function getPrompt(string $name): PromptReference;
+
+    /**
+     * Subscribes a session to a specific resource URI.
+     */
+    public function subscribe(SessionInterface $session, string $uri): void;
+
+    /**
+     * Unsubscribes a session from a specific resource URI.
+     */
+    public function unsubscribe(SessionInterface $session, string $uri): void;
+
+    /**
+     * Notifies all sessions subscribed to the given resource URI that the
+     * resource has changed. Sends a ResourceUpdatedNotification for each subscriber.
+     */
+    public function notifyResourceChanged(Protocol $protocol, string $uri): void;
 }

src/Server/Builder.php

@@ -488,7 +488,17 @@ public function build(): Server
     {
         $logger = $this->logger ?? new NullLogger();
         $container = $this->container ?? new Container();
-        $registry = $this->registry ?? new Registry($this->eventDispatcher, $logger);
+
+        $sessionTtl = $this->sessionTtl ?? 3600;
+        $sessionFactory = $this->sessionFactory ?? new SessionFactory();
+        $sessionStore = $this->sessionStore ?? new InMemorySessionStore($sessionTtl);
+
+        $registry = $this->registry ?? new Registry(
+            $this->eventDispatcher,
+            $logger,
+            $sessionStore,
+            $sessionFactory
+        );
 
         $loaders = [
             ...$this->loaders,
@@ -504,16 +514,13 @@ public function build(): Server
             $loader->load($registry);
         }
 
-        $sessionTtl = $this->sessionTtl ?? 3600;
-        $sessionFactory = $this->sessionFactory ?? new SessionFactory();
-        $sessionStore = $this->sessionStore ?? new InMemorySessionStore($sessionTtl);
         $messageFactory = MessageFactory::make();
 
         $capabilities = $this->serverCapabilities ?? new ServerCapabilities(
             tools: $registry->hasTools(),
             toolsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
             resources: $registry->hasResources() || $registry->hasResourceTemplates(),
-            resourcesSubscribe: false,
+            resourcesSubscribe: $registry->hasResources() || $registry->hasResourceTemplates(),
             resourcesListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
             prompts: $registry->hasPrompts(),
             promptsListChanged: $this->eventDispatcher instanceof EventDispatcherInterface,
@@ -536,6 +543,8 @@ public function build(): Server
             new Handler\Request\ListToolsHandler($registry, $this->paginationLimit),
             new Handler\Request\PingHandler(),
             new Handler\Request\ReadResourceHandler($registry, $referenceHandler, $logger),
+            new Handler\Request\ResourceSubscribeHandler($registry, $logger),
+            new Handler\Request\ResourceUnsubscribeHandler($registry, $logger),
             new Handler\Request\SetLogLevelHandler(),
         ]);
 

src/Server/Handler/Request/ResourceSubscribeHandler.php

@@ -0,0 +1,66 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Handler\Request;
+
+use Mcp\Capability\RegistryInterface;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Schema\JsonRpc\Error;
+use Mcp\Schema\JsonRpc\Request;
+use Mcp\Schema\JsonRpc\Response;
+use Mcp\Schema\Request\ResourceSubscribeRequest;
+use Mcp\Schema\Result\EmptyResult;
+use Mcp\Server\Session\SessionInterface;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+
+/**
+ * @implements RequestHandlerInterface<EmptyResult>
+ *
+ * @author Larry Sule-balogun <suleabimbola@gmail.com>
+ */
+final class ResourceSubscribeHandler implements RequestHandlerInterface
+{
+    public function __construct(
+        private readonly RegistryInterface $registry,
+        private readonly LoggerInterface $logger = new NullLogger(),
+    ) {
+    }
+
+    public function supports(Request $request): bool
+    {
+        return $request instanceof ResourceSubscribeRequest;
+    }
+
+    public function handle(Request $request, SessionInterface $session): Response|Error
+    {
+        \assert($request instanceof ResourceSubscribeRequest);
+
+        $uri = $request->uri;
+
+        try {
+            $this->registry->getResource($uri);
+        } catch (ResourceNotFoundException $e) {
+            $this->logger->error('Resource not found', ['uri' => $uri]);
+
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
+        }
+
+        $this->logger->debug('Subscribing to resource', ['uri' => $uri]);
+
+        $this->registry->subscribe($session, $uri);
+
+        return new Response(
+            $request->getId(),
+            new EmptyResult(),
+        );
+    }
+}

src/Server/Handler/Request/ResourceUnsubscribeHandler.php

@@ -0,0 +1,66 @@
+<?php
+
+/*
+ * This file is part of the official PHP MCP SDK.
+ *
+ * A collaboration between Symfony and the PHP Foundation.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Mcp\Server\Handler\Request;
+
+use Mcp\Capability\RegistryInterface;
+use Mcp\Exception\ResourceNotFoundException;
+use Mcp\Schema\JsonRpc\Error;
+use Mcp\Schema\JsonRpc\Request;
+use Mcp\Schema\JsonRpc\Response;
+use Mcp\Schema\Request\ResourceUnsubscribeRequest;
+use Mcp\Schema\Result\EmptyResult;
+use Mcp\Server\Session\SessionInterface;
+use Psr\Log\LoggerInterface;
+use Psr\Log\NullLogger;
+
+/**
+ * @implements RequestHandlerInterface<EmptyResult>
+ *
+ * @author Larry Sule-balogun <suleabimbola@gmail.com>
+ */
+final class ResourceUnsubscribeHandler implements RequestHandlerInterface
+{
+    public function __construct(
+        private readonly RegistryInterface $registry,
+        private readonly LoggerInterface $logger = new NullLogger(),
+    ) {
+    }
+
+    public function supports(Request $request): bool
+    {
+        return $request instanceof ResourceUnsubscribeRequest;
+    }
+
+    public function handle(Request $request, SessionInterface $session): Response|Error
+    {
+        \assert($request instanceof ResourceUnsubscribeRequest);
+
+        $uri = $request->uri;
+
+        try {
+            $this->registry->getResource($uri);
+        } catch (ResourceNotFoundException $e) {
+            $this->logger->error('Resource not found', ['uri' => $uri]);
+
+            return Error::forResourceNotFound($e->getMessage(), $request->getId());
+        }
+
+        $this->logger->debug('Unsubscribing from resource', ['uri' => $uri]);
+
+        $this->registry->unsubscribe($session, $uri);
+
+        return new Response(
+            $request->getId(),
+            new EmptyResult(),
+        );
+    }
+}

src/Server/Session/FileSessionStore.php

@@ -150,6 +150,44 @@ public function gc(): array
         return $deleted;
     }
 
+    public function getAllSessionIds(): array
+    {
+        $sessionIds = [];
+        $now = $this->clock->now()->getTimestamp();
+
+        $dir = @opendir($this->directory);
+        if (false === $dir) {
+            return $sessionIds;
+        }
+
+        while (($entry = readdir($dir)) !== false) {
+            // Skip dot entries
+            if ('.' === $entry || '..' === $entry) {
+                continue;
+            }
+
+            $path = $this->directory.\DIRECTORY_SEPARATOR.$entry;
+            if (!is_file($path)) {
+                continue;
+            }
+
+            $mtime = @filemtime($path) ?: 0;
+            if (($now - $mtime) > $this->ttl) {
+                continue;
+            }
+
+            try {
+                $sessionIds[] = Uuid::fromString($entry);
+            } catch (\Throwable) {
+                // ignore non-UUID file names
+            }
+        }
+
+        closedir($dir);
+
+        return $sessionIds;
+    }
+
     private function pathFor(Uuid $id): string
     {
         return $this->directory.\DIRECTORY_SEPARATOR.$id->toRfc4122();

src/Server/Session/InMemorySessionStore.php

@@ -87,4 +87,14 @@ public function gc(): array
 
         return $deletedSessions;
     }
+
+    public function getAllSessionIds(): array
+    {
+        $ids = [];
+        foreach (array_keys($this->store) as $id) {
+            $ids[] = Uuid::fromString($id);
+        }
+
+        return $ids;
+    }
 }