cluster: use Map to track handles in cluster child

PR-URL: https://github.com/nodejs/node/pull/23125
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Denys Otrishko <shishugi@gmail.com>

lib/internal/cluster/child.js

@@ -7,7 +7,7 @@ const { owner_symbol } = require('internal/async_hooks').symbols;
 const Worker = require('internal/cluster/worker');
 const { internal, sendHelper } = require('internal/cluster/utils');
 const cluster = new EventEmitter();
-const handles = {};
+const handles = new Map();
 const indexes = new Map();
 const noop = () => {};
 
@@ -111,12 +111,12 @@ function shared(message, handle, indexesKey, cb) {
 
   handle.close = function() {
     send({ act: 'close', key });
-    delete handles[key];
+    handles.delete(key);
     indexes.delete(indexesKey);
     return close.apply(this, arguments);
   }.bind(handle);
-  assert(handles[key] === undefined);
+  assert(handles.has(key) === false);
-  handles[key] = handle;
+  handles.set(key, handle);
   cb(message.errno, handle);
 }
 
@@ -144,7 +144,7 @@ function rr(message, indexesKey, cb) {
       return;
 
     send({ act: 'close', key });
-    delete handles[key];
+    handles.delete(key);
     indexes.delete(indexesKey);
     key = undefined;
   }
@@ -166,15 +166,15 @@ function rr(message, indexesKey, cb) {
     handle.getsockname = getsockname;  // TCP handles only.
   }
 
-  assert(handles[key] === undefined);
+  assert(handles.has(key) === false);
-  handles[key] = handle;
+  handles.set(key, handle);
   cb(0, handle);
 }
 
 // Round-robin connection.
 function onconnection(message, handle) {
   const key = message.key;
-  const server = handles[key];
+  const server = handles.get(key);
   const accepted = server !== undefined;
 
   send({ ack: message.seq, accepted });
@@ -207,17 +207,16 @@ function _disconnect(masterInitiated) {
     }
   }
 
-  for (var key in handles) {
+  handles.forEach((handle) => {
-    const handle = handles[key];
-    delete handles[key];
     waitingCount++;
 
     if (handle[owner_symbol])
       handle[owner_symbol].close(checkWaitingCount);
     else
       handle.close(checkWaitingCount);
-  }
+  });
 
+  handles.clear();
   checkWaitingCount();
 }