http: start connections checking interval on listen

Fixes: nodejs#48604.

lib/_http_server.js

@@ -498,6 +498,10 @@ function storeHTTPOptions(options) {
 }
 
 function setupConnectionsTracking(server) {
+  if (!server) {
+    server = this;
+  }
+
   // Start connection handling
   server[kConnections] = new ConnectionsList();
 
@@ -542,11 +546,12 @@ function Server(options, requestListener) {
   this.httpAllowHalfOpen = false;
 
   this.on('connection', connectionListener);
+  this.on('listening', setupConnectionsTracking, this);
 
   this.timeout = 0;
   this.maxHeadersCount = null;
   this.maxRequestsPerSocket = 0;
-  setupConnectionsTracking(this);
+
   this[kUniqueHeaders] = parseUniqueHeadersOption(options.uniqueHeaders);
 }
 ObjectSetPrototypeOf(Server.prototype, net.Server.prototype);
@@ -558,15 +563,15 @@ Server.prototype.close = function() {
 };
 
 Server.prototype.closeAllConnections = function() {
-  const connections = this[kConnections].all();
+  const connections = this[kConnections]?.all() ?? [];
 
   for (let i = 0, l = connections.length; i < l; i++) {
     connections[i].socket.destroy();
   }
 };
 
 Server.prototype.closeIdleConnections = function() {
-  const connections = this[kConnections].idle();
+  const connections = this[kConnections]?.idle() ?? [];
 
   for (let i = 0, l = connections.length; i < l; i++) {
     if (connections[i].socket._httpMessage && !connections[i].socket._httpMessage.finished) {

test/parallel/test-http-server-connections-checking-leak.js

@@ -0,0 +1,32 @@
+'use strict';
+
+// Flags: --expose-gc
+
+require('../common');
+const assert = require('assert');
+const http = require('http');
+
+// Check that creating a server without listening is not leaking resources.
+
+const step = 10000;
+const max = 100000;
+
+const usages = [];
+
+for (let i = 0; i < max; i++) {
+  if (i % 100 === 0) {
+    global.gc();
+  }
+
+  if (i % step === 0) {
+    usages.push(process.memoryUsage());
+  }
+
+  http.createServer((req, res) => {});
+}
+
+for (let i = 1; i < usages.length; i++) {
+  const current = usages[i].heapTotal;
+  const reference = usages[0].heapTotal;
+  assert.ok(current / reference < 1.1, `memory usage is increasing (${i}): ${current} > ${reference} * 1.1`);
+}