lib: add signalMonitor event for process

Author: chenyuebiao

doc/api/process.md

@@ -625,6 +625,17 @@ added:
 
 The `'worker'` event is emitted after a new {Worker} thread has been created.
 
+### Event: `'signalMonitor'`
+
+<!-- YAML
+added:
+  - REPLACEME
+-->
+
+* `signal` {string} The signal name, such as `SIGINT`.
+
+The `'signalMonitor'` event is emitted after a signal is received.
+
 ### Signal events
 
 <!--type=event-->

lib/events.js

@@ -83,6 +83,7 @@ const {
   validateString,
 } = require('internal/validators');
 const { addAbortListener } = require('internal/events/abort_listener');
+const { signals } = internalBinding('constants').os;
 
 const kCapture = Symbol('kCapture');
 const kErrorMonitor = Symbol('events.errorMonitor');
@@ -454,6 +455,10 @@ function enhanceStackTrace(err, own) {
  * @returns {boolean}
  */
 EventEmitter.prototype.emit = function emit(type, ...args) {
+  if (this === process && signals[type] !== undefined) {
+    process.emit('signalMonitor', type);
+  }
+
   let doError = (type === 'error');
 
   const events = this._events;

test/parallel/test-event-emitter-signal-monitor.js

@@ -0,0 +1,18 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const EventEmitter = require('events');
+
+// Test that EventEmitter.signalMonitor is not called on EE.
+const EE = new EventEmitter();
+EE.on('signalMonitor', common.mustNotCall());
+EE.emit('SIGINT');
+
+// Test that EventEmitter.signalMonitor is called on process.
+process.on('signalMonitor', common.mustCall(function(signal) {
+  assert.strictEqual(signal, 'SIGINT');
+}, 1));
+process.emit('SIGINT');
+
+// Test that EventEmitter.signalMonitor is not called on other events.
+process.emit('test');