fix(server): address domain performance regression with Node v12.x (#1809)

Author: Peter Marton

lib/server.js

@@ -2,7 +2,6 @@
 
 'use strict';
 
-var domain = require('domain');
 var EventEmitter = require('events').EventEmitter;
 var http = require('http');
 var https = require('https');
@@ -27,6 +26,7 @@ var customErrorTypes = require('./errorTypes');
 var patchRequest = require('./request');
 var patchResponse = require('./response');
 
+var domain;
 var http2;
 
 patchResponse(http.ServerResponse);
@@ -930,6 +930,14 @@ Server.prototype._onRequest = function _onRequest(req, res) {
     // It has significant negative performance impact
     // Warning: this feature depends on the deprecated domains module
     if (self.handleUncaughtExceptions) {
+        // In Node v12.x requiring the domain module has a negative performance
+        // impact. As using domains in restify is optional and only required
+        // with the `handleUncaughtExceptions` options, we apply a singleton
+        // pattern to avoid any performance regression in the default scenario.
+        if (!domain) {
+            domain = require('domain');
+        }
+
         var handlerDomain = domain.create();
         handlerDomain.add(req);
         handlerDomain.add(res);

package.json

@@ -108,7 +108,7 @@
     "once": "^1.4.0",
     "pidusage": "^2.0.17",
     "qs": "^6.7.0",
-    "restify-errors": "^8.0.0",
+    "restify-errors": "^8.0.2",
     "semver": "^6.1.1",
     "send": "^0.16.2",
     "spdy": "^4.0.0",