timers: make timer.refresh() a public API

Originally added in
bb5575a
discussions such as
#20261
show the usefulness of this API to the Node.js ecosystem.

PR-URL: #20298

Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ujjwal Sharma <usharma1998@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>

doc/api/timers.md

@@ -74,6 +74,21 @@ When called, requests that the Node.js event loop *not* exit so long as the
 By default, all `Timeout` objects are "ref'ed", making it normally unnecessary
 to call `timeout.ref()` unless `timeout.unref()` had been called previously.
 
+### timeout.refresh()
+<!-- YAML
+added: REPLACEME
+-->
+
+* Returns: {Timeout} a reference to `timeout`
+
+Sets the timer's start time to the current time, and reschedules the timer to
+call its callback at the previously specified duration adjusted to the current
+time. This is useful for refreshing a timer without allocating a new
+JavaScript object.
+
+Using this on a timer that has already called its callback will reactivate the
+timer.
+
 ### timeout.unref()
 <!-- YAML
 added: v0.9.1

lib/internal/http2/core.js

@@ -107,8 +107,7 @@ const {
 const {
   kTimeout,
   setUnrefTimeout,
-  validateTimerDuration,
-  refreshFnSymbol
+  validateTimerDuration
 } = require('internal/timers');
 const {
   createWriteWrap,
@@ -962,7 +961,7 @@ class Http2Session extends EventEmitter {
   [kUpdateTimer]() {
     if (this.destroyed)
       return;
-    if (this[kTimeout]) this[kTimeout][refreshFnSymbol]();
+    if (this[kTimeout]) this[kTimeout].refresh();
   }
 
   // Sets the id of the next stream to be created by this Http2Session.
@@ -1539,7 +1538,7 @@ class Http2Stream extends Duplex {
     if (this.destroyed)
       return;
     if (this[kTimeout])
-      this[kTimeout][refreshFnSymbol]();
+      this[kTimeout].refresh();
     if (this[kSession])
       this[kSession][kUpdateTimer]();
   }

lib/internal/timers.js

@@ -19,7 +19,6 @@ const {
 // Timeout values > TIMEOUT_MAX are set to 1.
 const TIMEOUT_MAX = 2 ** 31 - 1;
 
-const refreshFnSymbol = Symbol('refresh()');
 const unrefedSymbol = Symbol('unrefed');
 
 module.exports = {
@@ -29,7 +28,6 @@ module.exports = {
   trigger_async_id_symbol,
   Timeout,
   initAsyncResource,
-  refreshFnSymbol,
   setUnrefTimeout,
   validateTimerDuration
 };
@@ -82,7 +80,7 @@ function Timeout(callback, after, args, isRepeat, isUnrefed) {
   initAsyncResource(this, 'Timeout');
 }
 
-Timeout.prototype[refreshFnSymbol] = function refresh() {
+Timeout.prototype.refresh = function() {
   if (this._handle) {
     // Would be more ideal with uv_timer_again(), however that API does not
     // cause libuv's sorted timers data structure (a binary heap at the time
@@ -93,6 +91,8 @@ Timeout.prototype[refreshFnSymbol] = function refresh() {
   } else {
     getTimers().active(this);
   }
+
+  return this;
 };
 
 function setUnrefTimeout(callback, after, arg1, arg2, arg3) {

lib/net.js

@@ -89,8 +89,7 @@ const exceptionWithHostPort = errors.exceptionWithHostPort;
 const {
   kTimeout,
   setUnrefTimeout,
-  validateTimerDuration,
-  refreshFnSymbol
+  validateTimerDuration
 } = require('internal/timers');
 
 function noop() {}
@@ -325,7 +324,7 @@ util.inherits(Socket, stream.Duplex);
 Socket.prototype._unrefTimer = function _unrefTimer() {
   for (var s = this; s !== null; s = s._parent) {
     if (s[kTimeout])
-      s[kTimeout][refreshFnSymbol]();
+      s[kTimeout].refresh();
   }
 };
 

test/parallel/test-timers-refresh.js

@@ -5,7 +5,7 @@
 const common = require('../common');
 
 const { strictEqual } = require('assert');
-const { setUnrefTimeout, refreshFnSymbol } = require('internal/timers');
+const { setUnrefTimeout } = require('internal/timers');
 
 // Schedule the unrefed cases first so that the later case keeps the event loop
 // active.
@@ -27,7 +27,7 @@ const { setUnrefTimeout, refreshFnSymbol } = require('internal/timers');
     strictEqual(called, false, 'unref()\'d timer returned before check');
   }), 1);
 
-  timer[refreshFnSymbol]();
+  strictEqual(timer.refresh(), timer);
 }
 
 // unref pooled timer
@@ -41,7 +41,7 @@ const { setUnrefTimeout, refreshFnSymbol } = require('internal/timers');
     strictEqual(called, false, 'unref pooled timer returned before check');
   }), 1);
 
-  timer[refreshFnSymbol]();
+  strictEqual(timer.refresh(), timer);
 }
 
 // regular timer
@@ -55,5 +55,22 @@ const { setUnrefTimeout, refreshFnSymbol } = require('internal/timers');
     strictEqual(called, false, 'pooled timer returned before check');
   }), 1);
 
-  timer[refreshFnSymbol]();
+  strictEqual(timer.refresh(), timer);
+}
+
+// interval
+{
+  let called = 0;
+  const timer = setInterval(common.mustCall(() => {
+    called += 1;
+    if (called === 2) {
+      clearInterval(timer);
+    }
+  }, 2), 1);
+
+  setTimeout(common.mustCall(() => {
+    strictEqual(called, 0, 'pooled timer returned before check');
+  }), 1);
+
+  strictEqual(timer.refresh(), timer);
 }