fix: clean 'close' event listeners on socket server after generating new proxy config. (#5001)

Author: cwj0417

lib/Server.js

@@ -2087,6 +2087,12 @@ class Server {
 
             if (newProxyConfig !== proxyConfig) {
               proxyConfig = newProxyConfig;
+              const socket = req.socket != null ? req.socket : req.connection;
+              // @ts-ignore
+              const server = socket != null ? socket.server : null;
+              if (server) {
+                server.removeAllListeners("close");
+              }
               proxyMiddleware =
                 /** @type {RequestHandler} */
                 (getProxyMiddleware(proxyConfig));

test/server/proxy-option.test.js

@@ -75,9 +75,21 @@ const proxyOption = [
   },
 ];
 
+let maxServerListeners = 0;
 const proxyOptionOfArray = [
   { context: "/proxy1", target: `http://localhost:${port1}` },
   function proxy(req, res, next) {
+    if (req != null) {
+      const socket = req.socket != null ? req.socket : req.connection;
+      // @ts-ignore
+      const server = socket != null ? socket.server : null;
+      if (server) {
+        maxServerListeners = Math.max(
+          maxServerListeners,
+          server.listeners("close").length
+        );
+      }
+    }
     return {
       context: "/api/proxy2",
       target: `http://localhost:${port2}`,
@@ -463,6 +475,10 @@ describe("proxy option", () => {
       expect(response.statusCode).toEqual(200);
       expect(response.text).toEqual("foo+next+function");
     });
+
+    it("should not exist multiple close events registered", async () => {
+      expect(maxServerListeners).toBeLessThanOrEqual(1);
+    });
   });
 
   describe("as an array without the `route` option", () => {