feat(McpAsyncServer): Add non-blocking execution for tools and resources

- Execute tool calls, resource reads and prompt handling in a non-blocking
  manner using Schedulers.boundedElastic(). This prevents blocking operations
  from impacting server responsiveness.
- Added integration tests to verify non-blocking behavior with tools that
  make HTTP calls to external services.

Related to #48
This is  a temp patch until #48 is resolved properly.

Author: tzolov

README.md

@@ -32,14 +32,14 @@ Add the following dependencies to your Maven project:
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 
 <!-- For Spring AI integration -->
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>spring-ai-mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 ```
 

mcp-docs/src/main/antora/modules/ROOT/pages/mcp.adoc

@@ -25,7 +25,7 @@ Add the following dependency to your Maven project:
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 ----
 

mcp-docs/src/main/antora/modules/ROOT/pages/overview.adoc

@@ -40,7 +40,7 @@ Maven::
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 ----
 +
@@ -50,7 +50,7 @@ Maven::
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>spring-ai-mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 ----
 +

mcp-docs/src/main/antora/modules/ROOT/pages/spring-mcp.adoc

@@ -36,6 +36,6 @@ To use this module, add the following dependency to your Maven project:
 <dependency>
     <groupId>org.springframework.experimental</groupId>
     <artifactId>spring-ai-mcp</artifactId>
-    <version>0.4.0-SNAPSHOT</version>
+    <version>0.5.0-SNAPSHOT</version>
 </dependency>
 ----

mcp/src/main/java/org/springframework/ai/mcp/server/McpAsyncServer.java

@@ -374,9 +374,9 @@ private DefaultMcpSession.RequestHandler toolsCallRequestHandler() {
 				return Mono.<Object>error(new McpError("Tool not found: " + callToolRequest.name()));
 			}
 
-			CallToolResult callResponse = toolRegistration.get().call().apply(callToolRequest.arguments());
-
-			return Mono.just(callResponse);
+			return Mono.fromCallable(() -> toolRegistration.get().call().apply(callToolRequest.arguments()))
+				.map(result -> (Object) result)
+				.subscribeOn(Schedulers.boundedElastic());
 		};
 	}
 
@@ -462,7 +462,9 @@ private DefaultMcpSession.RequestHandler resourcesReadRequestHandler() {
 					});
 			var resourceUri = resourceRequest.uri();
 			if (this.resources.containsKey(resourceUri)) {
-				return Mono.just(this.resources.get(resourceUri).readHandler().apply(resourceRequest));
+				return Mono.fromCallable(() -> this.resources.get(resourceUri).readHandler().apply(resourceRequest))
+					.map(result -> (Object) result)
+					.subscribeOn(Schedulers.boundedElastic());
 			}
 			return Mono.error(new McpError("Resource not found: " + resourceUri));
 		};
@@ -558,7 +560,10 @@ private DefaultMcpSession.RequestHandler promptsGetRequestHandler() {
 
 			// Implement prompt retrieval logic here
 			if (this.prompts.containsKey(promptRequest.name())) {
-				return Mono.just(this.prompts.get(promptRequest.name()).promptHandler().apply(promptRequest));
+				return Mono
+					.fromCallable(() -> this.prompts.get(promptRequest.name()).promptHandler().apply(promptRequest))
+					.map(result -> (Object) result)
+					.subscribeOn(Schedulers.boundedElastic());
 			}
 
 			return Mono.error(new McpError("Prompt not found: " + promptRequest.name()));

mcp/src/test/java/org/springframework/ai/mcp/server/SseAsyncIntegrationTests.java

@@ -31,17 +31,22 @@
 
 import org.springframework.ai.mcp.client.McpClient;
 import org.springframework.ai.mcp.client.transport.SseClientTransport;
+import org.springframework.ai.mcp.server.McpServer.ToolRegistration;
 import org.springframework.ai.mcp.server.transport.SseServerTransport;
 import org.springframework.ai.mcp.spec.McpError;
 import org.springframework.ai.mcp.spec.McpSchema;
+import org.springframework.ai.mcp.spec.McpSchema.CallToolResult;
 import org.springframework.ai.mcp.spec.McpSchema.ClientCapabilities;
 import org.springframework.ai.mcp.spec.McpSchema.CreateMessageRequest;
 import org.springframework.ai.mcp.spec.McpSchema.CreateMessageResult;
 import org.springframework.ai.mcp.spec.McpSchema.InitializeResult;
 import org.springframework.ai.mcp.spec.McpSchema.Role;
 import org.springframework.ai.mcp.spec.McpSchema.Root;
+import org.springframework.ai.mcp.spec.McpSchema.ServerCapabilities;
+import org.springframework.ai.mcp.spec.McpSchema.Tool;
 import org.springframework.http.server.reactive.HttpHandler;
 import org.springframework.http.server.reactive.ReactorHttpHandlerAdapter;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.client.WebClient;
 import org.springframework.web.reactive.function.server.RouterFunctions;
 
@@ -314,4 +319,111 @@ void testRootsServerCloseWithActiveSubscription() {
 		mcpClient.close();
 	}
 
+	// ---------------------------------------
+	// Tools Tests
+	// ---------------------------------------
+	@Test
+	void testToolCallSuccess() {
+
+		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
+		ToolRegistration tool1 = new ToolRegistration(
+				new McpSchema.Tool("tool1", "tool1 description", Map.of("city", "String")), request -> {
+					// perform a blocking call to a remote service
+					String response = RestClient.create()
+						.get()
+						.uri("https://github.com/spring-projects-experimental/spring-ai-mcp/blob/main/README.md")
+						.retrieve()
+						.body(String.class);
+					assertThat(response).isNotBlank();
+					return callResponse;
+				});
+
+		var mcpServer = McpServer.using(mcpServerTransport)
+			.capabilities(ServerCapabilities.builder().tools(true).build())
+			.tools(tool1)
+			.sync();
+
+		var mcpClient = clientBuilder.sync();
+
+		InitializeResult initResult = mcpClient.initialize();
+		assertThat(initResult).isNotNull();
+
+		assertThat(mcpClient.listTools().tools()).contains(tool1.tool());
+
+		CallToolResult response = mcpClient.callTool(new McpSchema.CallToolRequest("tool1", Map.of()));
+
+		assertThat(response).isNotNull();
+		assertThat(response).isEqualTo(callResponse);
+
+		mcpClient.close();
+		mcpServer.close();
+	}
+
+	@Test
+	void testToolListChangeHandlingSuccess() {
+
+		var callResponse = new McpSchema.CallToolResult(List.of(new McpSchema.TextContent("CALL RESPONSE")), null);
+		ToolRegistration tool1 = new ToolRegistration(
+				new McpSchema.Tool("tool1", "tool1 description", Map.of("city", "String")), request -> {
+					// perform a blocking call to a remote service
+					String response = RestClient.create()
+						.get()
+						.uri("https://github.com/spring-projects-experimental/spring-ai-mcp/blob/main/README.md")
+						.retrieve()
+						.body(String.class);
+					assertThat(response).isNotBlank();
+					return callResponse;
+				});
+
+		var mcpServer = McpServer.using(mcpServerTransport)
+			.capabilities(ServerCapabilities.builder().tools(true).build())
+			.tools(tool1)
+			.sync();
+
+		AtomicReference<List<Tool>> rootsRef = new AtomicReference<>();
+		var mcpClient = clientBuilder.toolsChangeConsumer(toolsUpdate -> {
+			// perform a blocking call to a remote service
+			String response = RestClient.create()
+				.get()
+				.uri("https://github.com/spring-projects-experimental/spring-ai-mcp/blob/main/README.md")
+				.retrieve()
+				.body(String.class);
+			assertThat(response).isNotBlank();
+			rootsRef.set(toolsUpdate);
+		}).sync();
+
+		InitializeResult initResult = mcpClient.initialize();
+		assertThat(initResult).isNotNull();
+
+		assertThat(rootsRef.get()).isNull();
+
+		assertThat(mcpClient.listTools().tools()).contains(tool1.tool());
+
+		mcpServer.notifyToolsListChanged();
+
+		await().atMost(Duration.ofSeconds(5)).untilAsserted(() -> {
+			assertThat(rootsRef.get()).containsAll(List.of(tool1.tool()));
+		});
+
+		// Remove a tool
+		mcpServer.removeTool("tool1");
+
+		await().atMost(Duration.ofSeconds(5)).untilAsserted(() -> {
+			assertThat(rootsRef.get()).isEmpty();
+		});
+
+		// Add a new tool
+		ToolRegistration tool2 = new ToolRegistration(
+				new McpSchema.Tool("tool2", "tool2 description", Map.of("city", "String")), request -> callResponse);
+
+		mcpServer.addTool(tool2);
+
+		await().atMost(Duration.ofSeconds(5)).untilAsserted(() -> {
+			assertThat(rootsRef.get()).containsAll(List.of(tool2.tool()));
+		});
+
+		mcpClient.close();
+		mcpServer.close();
+	}
+
 }

spring-ai-mcp-sample/README.md

@@ -28,7 +28,7 @@ The server can be started in two transport modes, controlled by the `transport.m
 ### Stdio Mode (Default)
 
 ```bash
-java -Dtransport.mode=stdio -jar target/spring-ai-mcp-sample-0.4.0-SNAPSHOT.jar
+java -Dtransport.mode=stdio -jar target/spring-ai-mcp-sample-0.5.0-SNAPSHOT.jar
 ```
 
 The Stdio mode server is automatically started by the client - no explicit server startup is needed.
@@ -38,7 +38,7 @@ In Stdio mode the server must not emit any messages/logs to the console (e.g. st
 
 ### SSE Mode
 ```bash
-java -Dtransport.mode=sse -jar target/spring-ai-mcp-sample-0.4.0-SNAPSHOT.jar
+java -Dtransport.mode=sse -jar target/spring-ai-mcp-sample-0.5.0-SNAPSHOT.jar
 ```
 
 ## Sample Clients
@@ -49,7 +49,7 @@ The project includes example clients for both transport modes:
 ```java
 var stdioParams = ServerParameters.builder("java")
     .args("-Dtransport.mode=stdio", "-jar",
-            "target/spring-ai-mcp-sample-0.4.0-SNAPSHOT.jar")
+            "target/spring-ai-mcp-sample-0.5.0-SNAPSHOT.jar")
     .build();
 
 var transport = new StdioClientTransport(stdioParams);

spring-ai-mcp-sample/src/main/java/org/springframework/ai/mcp/sample/client/ClientStdio.java

@@ -28,7 +28,7 @@ public static void main(String[] args) {
 
 		var stdioParams = ServerParameters.builder("java")
 			.args("-Dtransport.mode=stdio", "-jar",
-					"spring-ai-mcp-sample/target/spring-ai-mcp-sample-0.4.0-SNAPSHOT.jar")
+					"spring-ai-mcp-sample/target/spring-ai-mcp-sample-0.5.0-SNAPSHOT.jar")
 			.build();
 
 		var transport = new StdioClientTransport(stdioParams);