child_process: fix memory leak in .fork()

Entries in the `net.Server#_slaves` array that is used to track handles sent from the master to workers were not deleted when a worker exited, resulting in a slow but inexorable memory leak. PR-URL: #15679 Backport-PR-URL: #16586Fixes: #15651 Reviewed-By: James M Snell <[email protected]> Reviewed-By: Luigi Pinca <[email protected]>

Author: bnoordhuis

lib/internal/socket_list.js

@@ -8,6 +8,7 @@ class SocketListSend extends EventEmitter{
 super();
 this.key=key;
 this.child=child;
+child.once('exit',()=>this.emit('exit',this));
 }
 
 _request(msg,cmd,callback){

lib/net.js

@@ -1664,6 +1664,10 @@ Server.prototype.listenFD = internalUtil.deprecate(function(fd, type){
 Server.prototype._setupSlave=function(socketList){
 this._usingSlaves=true;
 this._slaves.push(socketList);
+socketList.once('exit',(socketList)=>{
+constindex=this._slaves.indexOf(socketList);
+this._slaves.splice(index,1);
+});
 };
 
 Server.prototype.ref=function(){

test/parallel/test-child-process-fork-net2.js

@@ -156,6 +156,7 @@ if (process.argv[2] === 'child'){
 }
 
 process.on('exit',function(){
+assert.strictEqual(server._slaves.length,0);
 assert.strictEqual(disconnected,count);
 assert.strictEqual(connected,count);
 });