[fel] Add close support in McpClient and release resources properly

framework/fel/java/plugins/tool-mcp-client/src/main/java/modelengine/fel/tool/mcp/client/support/DefaultMcpClient.java

@@ -22,6 +22,7 @@
 import modelengine.fit.http.entity.TextEvent;
 import modelengine.fit.http.protocol.HttpRequestMethod;
 import modelengine.fitframework.flowable.Choir;
+import modelengine.fitframework.flowable.Subscription;
 import modelengine.fitframework.log.Logger;
 import modelengine.fitframework.schedule.ExecutePolicy;
 import modelengine.fitframework.schedule.Task;
@@ -76,6 +77,9 @@ public class DefaultMcpClient implements McpClient {
     private final Map<Long, Boolean> pendingRequests = new ConcurrentHashMap<>();
     private final Map<Long, Object> pendingResults = new ConcurrentHashMap<>();
 
+    private volatile Subscription subscription;
+    private volatile ThreadPoolScheduler pingScheduler;
+
     /**
      * Constructs a new instance of the DefaultMcpClient.
      *
@@ -113,11 +117,12 @@ public void initialize() {
         messages.subscribeOn(threadPool).subscribe(subscription -> {
                     log.info("Prepare to create SSE channel.");
                     subscription.request(Long.MAX_VALUE);
+                    this.subscription = subscription;
                 },
                 (subscription, textEvent) -> this.consumeTextEvent(textEvent),
                 subscription -> log.info("SSE channel is completed."),
                 (subscription, cause) -> log.error("SSE channel is failed.", cause));
-        ThreadPoolScheduler pingScheduler = ThreadPoolScheduler.custom()
+        this.pingScheduler = ThreadPoolScheduler.custom()
                 .threadPoolName("mcp-client-ping-" + this.name)
                 .awaitTermination(3, TimeUnit.SECONDS)
                 .isImmediateShutdown(true)
@@ -127,7 +132,7 @@ public void initialize() {
                 .workQueueCapacity(Integer.MAX_VALUE)
                 .isDaemonThread(true)
                 .build();
-        pingScheduler.schedule(Task.builder()
+        this.pingScheduler.schedule(Task.builder()
                 .runnable(this::pingServer)
                 .policy(ExecutePolicy.fixedDelay(DELAY_MILLIS))
                 .build(), DELAY_MILLIS);
@@ -375,4 +380,16 @@ private boolean waitInitialized() {
         }
         return this.initialized;
     }
+
+    @Override
+    public void close() throws IOException {
+        this.subscription.cancel();
+        try {
+            this.pingScheduler.shutdown();
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            throw new IOException(e);
+        }
+        log.info("Close MCP client. [name={}, sessionId={}]", this.name, this.sessionId);
+    }
 }

framework/fel/java/plugins/tool-mcp-test/src/main/java/modelengine/fel/tool/mcp/test/TestController.java

@@ -16,6 +16,7 @@
 import modelengine.fit.http.annotation.RequestQuery;
 import modelengine.fitframework.annotation.Component;
 
+import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 
@@ -55,6 +56,22 @@ public String initialize(@RequestQuery(name = "baseUri") String baseUri,
         return "Initialized";
     }
 
+    /**
+     * Closes the MCP client and releases any resources associated with it.
+     * This method ensures that the MCP client is properly closed and resources are released.
+     *
+     * @return A string indicating that the close operation was successful.
+     */
+    @PostMapping(path = "/close")
+    public String close() {
+        try {
+            this.client.close();
+        } catch (IOException e) {
+            throw new IllegalStateException("Failed to close.", e);
+        }
+        return "Closed";
+    }
+
     /**
      * Retrieves a list of available tools from the MCP server.
      * This method calls the MCP client to fetch the list of tools and returns it to the caller.

framework/fel/java/services/tool-mcp-client-service/src/main/java/modelengine/fel/tool/mcp/client/McpClient.java

@@ -8,6 +8,7 @@
 
 import modelengine.fel.tool.mcp.entity.Tool;
 
+import java.io.Closeable;
 import java.util.List;
 import java.util.Map;
 
@@ -20,7 +21,7 @@
  * @author 季聿阶
  * @since 2025-05-21
  */
-public interface McpClient {
+public interface McpClient extends Closeable {
     /**
      * Initializes the MCP Client.
      */