net: deprecate _setSimultaneousAccepts() undocumented function

This is an undocumented utility function that is of questionable utility. Fixes: #18391 PR-URL: #23760 Reviewed-By: Ben Noordhuis <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Michaël Zasso <[email protected]> Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Colin Ihrig <[email protected]>

Author: jasnell

doc/api/deprecations.md

@@ -2264,6 +2264,20 @@ undocumented `COUNTER_NET_SERVER_CONNECTION()`,
 `COUNTER_HTTP_SERVER_RESPONSE()`, `COUNTER_HTTP_CLIENT_REQUEST()`, and
 `COUNTER_HTTP_CLIENT_RESPONSE()` functions have been deprecated.
 
+<a id="DEP00XX"></a>
+### DEP00XX: net._setSimultaneousAccepts()
+<!-- YAML
+changes:
+ - version: REPLACEME
+ pr-url: https://github.com/nodejs/node/pull/23760
+ description: Runtime deprecation.
+-->
+
+The undocumented `net._setSimultaneousAccepts()` function was originally
+intended for debugging and performance tuning when using the `child_process`
+and `cluster` modules on Windows. The function is not generally useful and
+is being removed. See discussion here:
+https://github.com/nodejs/node/issues/18391
 
 [`--pending-deprecation`]: cli.html#cli_pending_deprecation
 [`Buffer.allocUnsafeSlow(size)`]: buffer.html#buffer_class_method_buffer_allocunsafeslow_size

lib/internal/child_process.js

@@ -604,8 +604,7 @@ function setupChannel(target, channel){
 
 // Update simultaneous accepts on Windows
 if(process.platform==='win32'){
-handle._simultaneousAccepts=false;
-net._setSimultaneousAccepts(handle);
+handle.setSimultaneousAccepts(false);
 }
 
 // Convert handle object
@@ -700,8 +699,8 @@ function setupChannel(target, channel){
 message=message.msg;
 
 // Update simultaneous accepts on Windows
-if(obj.simultaneousAccepts){
-net._setSimultaneousAccepts(handle);
+if(obj.simultaneousAccepts&&process.platform==='win32'){
+handle.setSimultaneousAccepts(true);
 }
 }elseif(this._handleQueue&&
 !(message&&(message.cmd==='NODE_HANDLE_ACK'||

lib/net.js

@@ -1668,11 +1668,18 @@ Server.prototype.unref = function(){
 };
 
 var_setSimultaneousAccepts;
+varwarnSimultaneousAccepts=true;
 
 if(process.platform==='win32'){
 varsimultaneousAccepts;
 
 _setSimultaneousAccepts=function(handle){
+if(warnSimultaneousAccepts){
+process.emitWarning(
+'net._setSimultaneousAccepts() is deprecated and will be removed.',
+'DeprecationWarning','DEP00XX');
+warnSimultaneousAccepts=false;
+}
 if(handle===undefined){
 return;
 }
@@ -1688,7 +1695,14 @@ if (process.platform === 'win32'){
 }
 };
 }else{
-_setSimultaneousAccepts=function(){};
+_setSimultaneousAccepts=function(){
+if(warnSimultaneousAccepts){
+process.emitWarning(
+'net._setSimultaneousAccepts() is deprecated and will be removed.',
+'DeprecationWarning','DEP00XX');
+warnSimultaneousAccepts=false;
+}
+};
 }
 
 module.exports={

test/parallel/test-net-deprecated-setsimultaneousaccepts.js

@@ -0,0 +1,16 @@
+// Flags: --no-warnings
+'use strict';
+
+const{
+ expectWarning
+}=require('../common');
+const{
+ _setSimultaneousAccepts
+}=require('net');
+
+expectWarning(
+'DeprecationWarning',
+'net._setSimultaneousAccepts() is deprecated and will be removed.',
+'DEP00XX');
+
+_setSimultaneousAccepts();