feat: Enhance Keep-Alive configuration handling (#455)

src/services/keepAliveService.ts

@@ -0,0 +1,73 @@
+import { SSEClientTransport } from '@modelcontextprotocol/sdk/client/sse.js';
+import { StreamableHTTPClientTransport } from '@modelcontextprotocol/sdk/client/streamableHttp.js';
+import { ServerInfo, ServerConfig } from '../types/index.js';
+
+export interface KeepAliveOptions {
+  enabled?: boolean;
+  intervalMs?: number;
+}
+
+/**
+ * Set up keep-alive ping for MCP client connections (SSE or Streamable HTTP).
+ * Keepalive is controlled per-server via `serverConfig.enableKeepAlive` (default off).
+ */
+export const setupClientKeepAlive = async (
+  serverInfo: ServerInfo,
+  serverConfig: ServerConfig,
+): Promise<void> => {
+  // Only set up keep-alive for SSE or Streamable HTTP client transports
+  const isSSE = serverInfo.transport instanceof SSEClientTransport;
+  const isStreamableHttp = serverInfo.transport instanceof StreamableHTTPClientTransport;
+  if (!isSSE && !isStreamableHttp) {
+    return;
+  }
+
+  const enabled = serverConfig.enableKeepAlive === true;
+  if (!enabled) {
+    // Ensure any previous timer is cleared
+    if (serverInfo.keepAliveIntervalId) {
+      clearInterval(serverInfo.keepAliveIntervalId as NodeJS.Timeout);
+      serverInfo.keepAliveIntervalId = undefined;
+    }
+    return;
+  }
+
+  // Clear any existing interval first
+  if (serverInfo.keepAliveIntervalId) {
+    clearInterval(serverInfo.keepAliveIntervalId as NodeJS.Timeout);
+  }
+
+  // Default interval: 60 seconds
+  const interval = serverConfig.keepAliveInterval || 60000;
+
+  serverInfo.keepAliveIntervalId = setInterval(async () => {
+    try {
+      if (serverInfo.client && serverInfo.status === 'connected') {
+        // Use client.ping() if available, otherwise fallback to listTools
+        if (typeof (serverInfo.client as any).ping === 'function') {
+          await (serverInfo.client as any).ping();
+          console.log(`Keep-alive ping successful for server: ${serverInfo.name}`);
+        } else {
+          await serverInfo.client.listTools({ timeout: 5000 }).catch(() => void 0);
+        }
+      }
+    } catch (error) {
+      console.warn(`Keep-alive ping failed for server ${serverInfo.name}:`, error);
+    }
+  }, interval);
+
+  console.log(
+    `Keep-alive enabled for server ${serverInfo.name} at ${Math.round(interval / 1000)}s interval`,
+  );
+};
+
+/**
+ * Clear keep-alive timer for a server.
+ */
+export const clearClientKeepAlive = (serverInfo: ServerInfo): void => {
+  if (serverInfo.keepAliveIntervalId) {
+    clearInterval(serverInfo.keepAliveIntervalId as NodeJS.Timeout);
+    serverInfo.keepAliveIntervalId = undefined;
+    console.log(`Cleared keep-alive interval for server: ${serverInfo.name}`);
+  }
+};