Enhance socket cleanup and management for improved connection handling

- Refactor cleanupSocket function to support options for immediate destruction, allowing drain, and grace periods.
- Introduce createIndependentSocketHandlers for better management of half-open connections between client and server sockets.
- Update various handlers (HTTP, HTTPS passthrough, HTTPS terminate) to utilize new cleanup and socket management functions.
- Implement custom timeout handling in socket setup to prevent immediate closure during keep-alive connections.
- Add tests for long-lived connections and half-open connection scenarios to ensure stability and reliability.
- Adjust connection manager to handle socket cleanup based on activity status, improving resource management.

ts/core/utils/socket-utils.ts

@@ -1,27 +1,62 @@
 import * as plugins from '../../plugins.js';
 
+export interface CleanupOptions {
+  immediate?: boolean;      // Force immediate destruction
+  allowDrain?: boolean;     // Allow write buffer to drain
+  gracePeriod?: number;     // Ms to wait before force close
+}
+
 /**
  * Safely cleanup a socket by removing all listeners and destroying it
  * @param socket The socket to cleanup
  * @param socketName Optional name for logging
+ * @param options Cleanup options
  */
-export function cleanupSocket(socket: plugins.net.Socket | plugins.tls.TLSSocket | null, socketName?: string): void {
-  if (!socket) return;
+export function cleanupSocket(
+  socket: plugins.net.Socket | plugins.tls.TLSSocket | null, 
+  socketName?: string,
+  options: CleanupOptions = {}
+): Promise<void> {
+  if (!socket || socket.destroyed) return Promise.resolve();
   
-  try {
-    // Remove all event listeners
-    socket.removeAllListeners();
+  return new Promise<void>((resolve) => {
+    const cleanup = () => {
+      try {
+        // Remove all event listeners
+        socket.removeAllListeners();
+        
+        // Destroy if not already destroyed
+        if (!socket.destroyed) {
+          socket.destroy();
+        }
+      } catch (err) {
+        console.error(`Error cleaning up socket${socketName ? ` (${socketName})` : ''}: ${err}`);
+      }
+      resolve();
+    };
     
-    // Unpipe any streams
-    socket.unpipe();
-    
-    // Destroy if not already destroyed
-    if (!socket.destroyed) {
-      socket.destroy();
+    if (options.immediate) {
+      // Immediate cleanup (old behavior)
+      socket.unpipe();
+      cleanup();
+    } else if (options.allowDrain && socket.writable) {
+      // Allow pending writes to complete
+      socket.end(() => cleanup());
+      
+      // Force cleanup after grace period
+      if (options.gracePeriod) {
+        setTimeout(() => {
+          if (!socket.destroyed) {
+            cleanup();
+          }
+        }, options.gracePeriod);
+      }
+    } else {
+      // Default: immediate cleanup
+      socket.unpipe();
+      cleanup();
     }
-  } catch (err) {
-    console.error(`Error cleaning up socket${socketName ? ` (${socketName})` : ''}: ${err}`);
-  }
+  });
 }
 
 /**
@@ -30,6 +65,7 @@ export function cleanupSocket(socket: plugins.net.Socket | plugins.tls.TLSSocket
  * @param serverSocket The server socket (optional)
  * @param onCleanup Optional callback when cleanup is done
  * @returns A cleanup function that can be called multiple times safely
+ * @deprecated Use createIndependentSocketHandlers for better half-open support
  */
 export function createSocketCleanupHandler(
   clientSocket: plugins.net.Socket | plugins.tls.TLSSocket,
@@ -42,10 +78,10 @@ export function createSocketCleanupHandler(
     if (cleanedUp) return;
     cleanedUp = true;
     
-    // Cleanup both sockets
-    cleanupSocket(clientSocket, 'client');
+    // Cleanup both sockets (old behavior - too aggressive)
+    cleanupSocket(clientSocket, 'client', { immediate: true });
     if (serverSocket) {
-      cleanupSocket(serverSocket, 'server');
+      cleanupSocket(serverSocket, 'server', { immediate: true });
     }
     
     // Call cleanup callback if provided
@@ -55,15 +91,79 @@ export function createSocketCleanupHandler(
   };
 }
 
+/**
+ * Create independent cleanup handlers for paired sockets that support half-open connections
+ * @param clientSocket The client socket
+ * @param serverSocket The server socket
+ * @param onBothClosed Callback when both sockets are closed
+ * @returns Independent cleanup functions for each socket
+ */
+export function createIndependentSocketHandlers(
+  clientSocket: plugins.net.Socket | plugins.tls.TLSSocket,
+  serverSocket: plugins.net.Socket | plugins.tls.TLSSocket,
+  onBothClosed: (reason: string) => void
+): { cleanupClient: (reason: string) => Promise<void>, cleanupServer: (reason: string) => Promise<void> } {
+  let clientClosed = false;
+  let serverClosed = false;
+  let clientReason = '';
+  let serverReason = '';
+  
+  const checkBothClosed = () => {
+    if (clientClosed && serverClosed) {
+      onBothClosed(`client: ${clientReason}, server: ${serverReason}`);
+    }
+  };
+  
+  const cleanupClient = async (reason: string) => {
+    if (clientClosed) return;
+    clientClosed = true;
+    clientReason = reason;
+    
+    // Allow server to continue if still active
+    if (!serverClosed && serverSocket.writable) {
+      // Half-close: stop reading from client, let server finish
+      clientSocket.pause();
+      clientSocket.unpipe(serverSocket);
+      await cleanupSocket(clientSocket, 'client', { allowDrain: true, gracePeriod: 5000 });
+    } else {
+      await cleanupSocket(clientSocket, 'client', { immediate: true });
+    }
+    
+    checkBothClosed();
+  };
+  
+  const cleanupServer = async (reason: string) => {
+    if (serverClosed) return;
+    serverClosed = true;
+    serverReason = reason;
+    
+    // Allow client to continue if still active
+    if (!clientClosed && clientSocket.writable) {
+      // Half-close: stop reading from server, let client finish
+      serverSocket.pause();
+      serverSocket.unpipe(clientSocket);
+      await cleanupSocket(serverSocket, 'server', { allowDrain: true, gracePeriod: 5000 });
+    } else {
+      await cleanupSocket(serverSocket, 'server', { immediate: true });
+    }
+    
+    checkBothClosed();
+  };
+  
+  return { cleanupClient, cleanupServer };
+}
+
 /**
  * Setup socket error and close handlers with proper cleanup
  * @param socket The socket to setup handlers for
  * @param handleClose The cleanup function to call
+ * @param handleTimeout Optional custom timeout handler
  * @param errorPrefix Optional prefix for error messages
  */
 export function setupSocketHandlers(
   socket: plugins.net.Socket | plugins.tls.TLSSocket,
   handleClose: (reason: string) => void,
+  handleTimeout?: (socket: plugins.net.Socket | plugins.tls.TLSSocket) => void,
   errorPrefix?: string
 ): void {
   socket.on('error', (error) => {
@@ -77,8 +177,12 @@ export function setupSocketHandlers(
   });
   
   socket.on('timeout', () => {
-    const prefix = errorPrefix || 'socket';
-    handleClose(`${prefix}_timeout`);
+    if (handleTimeout) {
+      handleTimeout(socket);  // Custom timeout handling
+    } else {
+      // Default: just log, don't close
+      console.warn(`Socket timeout: ${errorPrefix || 'socket'}`);
+    }
   });
 }