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|
'use strict';
const TimerWrap = process.binding('timer_wrap').Timer;
const L = require('internal/linkedlist');
const assert = require('assert');
const util = require('util');
const debug = util.debuglog('timer');
const kOnTimeout = TimerWrap.kOnTimeout | 0;
// Timeout values > TIMEOUT_MAX are set to 1.
const TIMEOUT_MAX = 2147483647; // 2^31-1
// HOW and WHY the timers implementation works the way it does.
//
// Timers are crucial to Node.js. Internally, any TCP I/O connection creates a
// timer so that we can time out of connections. Additionally, many user
// libraries and applications also use timers. As such there may be a
// significantly large amount of timeouts scheduled at any given time.
// Therefore, it is very important that the timers implementation is performant
// and efficient.
//
// Note: It is suggested you first read though the lib/internal/linkedlist.js
// linked list implementation, since timers depend on it extensively. It can be
// somewhat counter-intuitive at first, as it is not actually a class. Instead,
// it is a set of helpers that operate on an existing object.
//
// In order to be as performant as possible, the architecture and data
// structures are designed so that they are optimized to handle the following
// use cases as efficiently as possible:
// - Adding a new timer. (insert)
// - Removing an existing timer. (remove)
// - Handling a timer timing out. (timeout)
//
// Whenever possible, the implementation tries to make the complexity of these
// operations as close to constant-time as possible.
// (So that performance is not impacted by the number of scheduled timers.)
//
// Object maps are kept which contain linked lists keyed by their duration in
// milliseconds.
// The linked lists within also have some meta-properties, one of which is a
// TimerWrap C++ handle, which makes the call after the duration to process the
// list it is attached to.
//
//
// ╔════ > Object Map
// ║
// ╠══
// ║ refedLists: { '40': { }, '320': { etc } } (keys of millisecond duration)
// ╚══ ┌─────────┘
// │
// ╔══ │
// ║ TimersList { _idleNext: { }, _idlePrev: (self), _timer: (TimerWrap) }
// ║ ┌────────────────┘
// ║ ╔══ │ ^
// ║ ║ { _idleNext: { }, _idlePrev: { }, _onTimeout: (callback) }
// ║ ║ ┌───────────┘
// ║ ║ │ ^
// ║ ║ { _idleNext: { etc }, _idlePrev: { }, _onTimeout: (callback) }
// ╠══ ╠══
// ║ ║
// ║ ╚════ > Actual JavaScript timeouts
// ║
// ╚════ > Linked List
//
//
// With this, virtually constant-time insertion (append), removal, and timeout
// is possible in the JavaScript layer. Any one list of timers is able to be
// sorted by just appending to it because all timers within share the same
// duration. Therefore, any timer added later will always have been scheduled to
// timeout later, thus only needing to be appended.
// Removal from an object-property linked list is also virtually constant-time
// as can be seen in the lib/internal/linkedlist.js implementation.
// Timeouts only need to process any timers due to currently timeout, which will
// always be at the beginning of the list for reasons stated above. Any timers
// after the first one encountered that does not yet need to timeout will also
// always be due to timeout at a later time.
//
// Less-than constant time operations are thus contained in two places:
// TimerWrap's backing libuv timers implementation (a performant heap-based
// queue), and the object map lookup of a specific list by the duration of
// timers within (or creation of a new list).
// However, these operations combined have shown to be trivial in comparison to
// other alternative timers architectures.
// Object maps containing linked lists of timers, keyed and sorted by their
// duration in milliseconds.
//
// The difference between these two objects is that the former contains timers
// that will keep the process open if they are the only thing left, while the
// latter will not.
//
// - key = time in milliseconds
// - value = linked list
const refedLists = Object.create(null);
const unrefedLists = Object.create(null);
// Schedule or re-schedule a timer.
// The item must have been enroll()'d first.
const active = exports.active = function(item) {
insert(item, false);
};
// Internal APIs that need timeouts should use `_unrefActive()` instead of
// `active()` so that they do not unnecessarily keep the process open.
exports._unrefActive = function(item) {
insert(item, true);
};
// The underlying logic for scheduling or re-scheduling a timer.
//
// Appends a timer onto the end of an existing timers list, or creates a new
// TimerWrap backed list if one does not already exist for the specified timeout
// duration.
function insert(item, unrefed) {
const msecs = item._idleTimeout;
if (msecs < 0 || msecs === undefined) return;
item._idleStart = TimerWrap.now();
const lists = unrefed === true ? unrefedLists : refedLists;
// Use an existing list if there is one, otherwise we need to make a new one.
var list = lists[msecs];
if (!list) {
debug('no %d list was found in insert, creating a new one', msecs);
lists[msecs] = list = createTimersList(msecs, unrefed);
}
L.append(list, item);
assert(!L.isEmpty(list)); // list is not empty
}
function createTimersList(msecs, unrefed) {
// Make a new linked list of timers, and create a TimerWrap to schedule
// processing for the list.
const list = new TimersList(msecs, unrefed);
L.init(list);
list._timer._list = list;
if (unrefed === true) list._timer.unref();
list._timer.start(msecs);
list._timer[kOnTimeout] = listOnTimeout;
return list;
}
function TimersList(msecs, unrefed) {
this._idleNext = null; // Create the list with the linkedlist properties to
this._idlePrev = null; // prevent any unnecessary hidden class changes.
this._timer = new TimerWrap();
this._unrefed = unrefed;
this.msecs = msecs;
this.nextTick = false;
}
function listOnTimeout() {
var list = this._list;
var msecs = list.msecs;
if (list.nextTick) {
list.nextTick = false;
process.nextTick(listOnTimeoutNT, list);
return;
}
debug('timeout callback %d', msecs);
var now = TimerWrap.now();
debug('now: %d', now);
var diff, timer;
while (timer = L.peek(list)) {
diff = now - timer._idleStart;
// Check if this loop iteration is too early for the next timer.
// This happens if there are more timers scheduled for later in the list.
if (diff < msecs) {
var timeRemaining = msecs - (TimerWrap.now() - timer._idleStart);
if (timeRemaining < 0) {
timeRemaining = 0;
}
this.start(timeRemaining);
debug('%d list wait because diff is %d', msecs, diff);
return;
}
// The actual logic for when a timeout happens.
L.remove(timer);
assert(timer !== L.peek(list));
if (!timer._onTimeout) continue;
var domain = timer.domain;
if (domain) {
// If the timer callback throws and the
// domain or uncaughtException handler ignore the exception,
// other timers that expire on this tick should still run.
//
// https://github.com/nodejs/node-v0.x-archive/issues/2631
if (domain._disposed)
continue;
domain.enter();
}
tryOnTimeout(timer, list);
if (domain)
domain.exit();
}
// If `L.peek(list)` returned nothing, the list was either empty or we have
// called all of the timer timeouts.
// As such, we can remove the list and clean up the TimerWrap C++ handle.
debug('%d list empty', msecs);
assert(L.isEmpty(list));
this.close();
// Either refedLists[msecs] or unrefedLists[msecs] may have been removed and
// recreated since the reference to `list` was created. Make sure they're
// the same instance of the list before destroying.
if (list._unrefed === true && list === unrefedLists[msecs]) {
delete unrefedLists[msecs];
} else if (list === refedLists[msecs]) {
delete refedLists[msecs];
}
}
// An optimization so that the try/finally only de-optimizes (since at least v8
// 4.7) what is in this smaller function.
function tryOnTimeout(timer, list) {
timer._called = true;
var threw = true;
try {
ontimeout(timer);
threw = false;
} finally {
if (!threw) return;
// Postpone all later list events to next tick. We need to do this
// so that the events are called in the order they were created.
const lists = list._unrefed === true ? unrefedLists : refedLists;
for (var key in lists) {
if (key > list.msecs) {
lists[key].nextTick = true;
}
}
// We need to continue processing after domain error handling
// is complete, but not by using whatever domain was left over
// when the timeout threw its exception.
const domain = process.domain;
process.domain = null;
// If we threw, we need to process the rest of the list in nextTick.
process.nextTick(listOnTimeoutNT, list);
process.domain = domain;
}
}
function listOnTimeoutNT(list) {
list._timer[kOnTimeout]();
}
// A convenience function for re-using TimerWrap handles more easily.
//
// This mostly exists to fix https://github.com/nodejs/node/issues/1264.
// Handles in libuv take at least one `uv_run` to be registered as unreferenced.
// Re-using an existing handle allows us to skip that, so that a second `uv_run`
// will return no active handles, even when running `setTimeout(fn).unref()`.
function reuse(item) {
L.remove(item);
var list = refedLists[item._idleTimeout];
// if empty - reuse the watcher
if (list && L.isEmpty(list)) {
debug('reuse hit');
list._timer.stop();
delete refedLists[item._idleTimeout];
return list._timer;
}
return null;
}
// Remove a timer. Cancels the timeout and resets the relevant timer properties.
const unenroll = exports.unenroll = function(item) {
var handle = reuse(item);
if (handle) {
debug('unenroll: list empty');
handle.close();
}
// if active is called later, then we want to make sure not to insert again
item._idleTimeout = -1;
};
// Make a regular object able to act as a timer by setting some properties.
// This function does not start the timer, see `active()`.
// Using existing objects as timers slightly reduces object overhead.
exports.enroll = function(item, msecs) {
if (typeof msecs !== 'number') {
throw new TypeError('"msecs" argument must be a number');
}
if (msecs < 0 || !isFinite(msecs)) {
throw new RangeError('"msecs" argument must be ' +
'a non-negative finite number');
}
// if this item was already in a list somewhere
// then we should unenroll it from that
if (item._idleNext) unenroll(item);
// Ensure that msecs fits into signed int32
if (msecs > TIMEOUT_MAX) {
msecs = TIMEOUT_MAX;
}
item._idleTimeout = msecs;
L.init(item);
};
/*
* DOM-style timers
*/
exports.setTimeout = function(callback, after, arg1, arg2, arg3) {
if (typeof callback !== 'function') {
throw new TypeError('"callback" argument must be a function');
}
var len = arguments.length;
var args;
if (len === 3) {
args = [arg1];
} else if (len === 4) {
args = [arg1, arg2];
} else if (len > 4) {
args = [arg1, arg2, arg3];
for (var i = 5; i < len; i++)
// extend array dynamically, makes .apply run much faster in v6.0.0
args[i - 2] = arguments[i];
}
return createSingleTimeout(callback, after, args);
};
function createSingleTimeout(callback, after, args) {
after *= 1; // coalesce to number or NaN
if (!(after >= 1 && after <= TIMEOUT_MAX))
after = 1; // schedule on next tick, follows browser behaviour
var timer = new Timeout(after, callback, args);
if (process.domain)
timer.domain = process.domain;
active(timer);
return timer;
}
function ontimeout(timer) {
var args = timer._timerArgs;
var callback = timer._onTimeout;
if (!args)
callback.call(timer);
else {
switch (args.length) {
case 1:
callback.call(timer, args[0]);
break;
case 2:
callback.call(timer, args[0], args[1]);
break;
case 3:
callback.call(timer, args[0], args[1], args[2]);
break;
default:
callback.apply(timer, args);
}
}
if (timer._repeat)
rearm(timer);
}
function rearm(timer) {
// // Do not re-arm unenroll'd or closed timers.
if (timer._idleTimeout === -1) return;
// If timer is unref'd (or was - it's permanently removed from the list.)
if (timer._handle && timer instanceof Timeout) {
timer._handle.start(timer._repeat);
} else {
timer._idleTimeout = timer._repeat;
active(timer);
}
}
const clearTimeout = exports.clearTimeout = function(timer) {
if (timer && (timer[kOnTimeout] || timer._onTimeout)) {
timer[kOnTimeout] = timer._onTimeout = null;
if (timer instanceof Timeout) {
timer.close(); // for after === 0
} else {
unenroll(timer);
}
}
};
exports.setInterval = function(callback, repeat, arg1, arg2, arg3) {
if (typeof callback !== 'function') {
throw new TypeError('"callback" argument must be a function');
}
var len = arguments.length;
var args;
if (len === 3) {
args = [arg1];
} else if (len === 4) {
args = [arg1, arg2];
} else if (len > 4) {
args = [arg1, arg2, arg3];
for (var i = 5; i < len; i++)
// extend array dynamically, makes .apply run much faster in v6.0.0
args[i - 2] = arguments[i];
}
return createRepeatTimeout(callback, repeat, args);
};
function createRepeatTimeout(callback, repeat, args) {
repeat *= 1; // coalesce to number or NaN
if (!(repeat >= 1 && repeat <= TIMEOUT_MAX))
repeat = 1; // schedule on next tick, follows browser behaviour
var timer = new Timeout(repeat, callback, args);
timer._repeat = repeat;
if (process.domain)
timer.domain = process.domain;
active(timer);
return timer;
}
exports.clearInterval = function(timer) {
if (timer && timer._repeat) {
timer._repeat = null;
clearTimeout(timer);
}
};
function Timeout(after, callback, args) {
this._called = false;
this._idleTimeout = after;
this._idlePrev = this;
this._idleNext = this;
this._idleStart = null;
this._onTimeout = callback;
this._timerArgs = args;
this._repeat = null;
}
function unrefdHandle() {
// Don't attempt to call the callback if it is not a function.
if (typeof this.owner._onTimeout === 'function') {
ontimeout(this.owner);
}
// Make sure we clean up if the callback is no longer a function
// even if the timer is an interval.
if (!this.owner._repeat ||
typeof this.owner._onTimeout !== 'function') {
this.owner.close();
}
}
Timeout.prototype.unref = function() {
if (this._handle) {
this._handle.unref();
} else if (typeof this._onTimeout === 'function') {
var now = TimerWrap.now();
if (!this._idleStart) this._idleStart = now;
var delay = this._idleStart + this._idleTimeout - now;
if (delay < 0) delay = 0;
// Prevent running cb again when unref() is called during the same cb
if (this._called && !this._repeat) {
unenroll(this);
return;
}
var handle = reuse(this);
this._handle = handle || new TimerWrap();
this._handle.owner = this;
this._handle[kOnTimeout] = unrefdHandle;
this._handle.start(delay);
this._handle.domain = this.domain;
this._handle.unref();
}
return this;
};
Timeout.prototype.ref = function() {
if (this._handle)
this._handle.ref();
return this;
};
Timeout.prototype.close = function() {
this._onTimeout = null;
if (this._handle) {
this._idleTimeout = -1;
this._handle[kOnTimeout] = null;
this._handle.close();
} else {
unenroll(this);
}
return this;
};
// A linked list for storing `setImmediate()` requests
function ImmediateList() {
this.head = null;
this.tail = null;
}
// Appends an item to the end of the linked list, adjusting the current tail's
// previous and next pointers where applicable
ImmediateList.prototype.append = function(item) {
if (this.tail) {
this.tail._idleNext = item;
item._idlePrev = this.tail;
} else {
this.head = item;
}
this.tail = item;
};
// Removes an item from the linked list, adjusting the pointers of adjacent
// items and the linked list's head or tail pointers as necessary
ImmediateList.prototype.remove = function(item) {
if (item._idleNext) {
item._idleNext._idlePrev = item._idlePrev;
}
if (item._idlePrev) {
item._idlePrev._idleNext = item._idleNext;
}
if (item === this.head)
this.head = item._idleNext;
if (item === this.tail)
this.tail = item._idlePrev;
item._idleNext = null;
item._idlePrev = null;
};
// Create a single linked list instance only once at startup
var immediateQueue = new ImmediateList();
function processImmediate() {
var immediate = immediateQueue.head;
var tail = immediateQueue.tail;
var domain;
// Clear the linked list early in case new `setImmediate()` calls occur while
// immediate callbacks are executed
immediateQueue.head = immediateQueue.tail = null;
while (immediate) {
domain = immediate.domain;
if (!immediate._onImmediate) {
immediate = immediate._idleNext;
continue;
}
if (domain)
domain.enter();
immediate._callback = immediate._onImmediate;
// Save next in case `clearImmediate(immediate)` is called from callback
var next = immediate._idleNext;
tryOnImmediate(immediate, tail);
if (domain)
domain.exit();
// If `clearImmediate(immediate)` wasn't called from the callback, use the
// `immediate`'s next item
if (immediate._idleNext)
immediate = immediate._idleNext;
else
immediate = next;
}
// Only round-trip to C++ land if we have to. Calling clearImmediate() on an
// immediate that's in |queue| is okay. Worst case is we make a superfluous
// call to NeedImmediateCallbackSetter().
if (!immediateQueue.head) {
process._needImmediateCallback = false;
}
}
// An optimization so that the try/finally only de-optimizes (since at least v8
// 4.7) what is in this smaller function.
function tryOnImmediate(immediate, oldTail) {
var threw = true;
try {
// make the actual call outside the try/catch to allow it to be optimized
runCallback(immediate);
threw = false;
} finally {
if (threw && immediate._idleNext) {
// Handle any remaining on next tick, assuming we're still alive to do so.
const curHead = immediateQueue.head;
const next = immediate._idleNext;
if (curHead) {
curHead._idlePrev = oldTail;
oldTail._idleNext = curHead;
next._idlePrev = null;
immediateQueue.head = next;
} else {
immediateQueue.head = next;
immediateQueue.tail = oldTail;
}
process.nextTick(processImmediate);
}
}
}
function runCallback(timer) {
const argv = timer._argv;
const argc = argv ? argv.length : 0;
switch (argc) {
// fast-path callbacks with 0-3 arguments
case 0:
return timer._callback();
case 1:
return timer._callback(argv[0]);
case 2:
return timer._callback(argv[0], argv[1]);
case 3:
return timer._callback(argv[0], argv[1], argv[2]);
// more than 3 arguments run slower with .apply
default:
return timer._callback.apply(timer, argv);
}
}
function Immediate() {
// assigning the callback here can cause optimize/deoptimize thrashing
// so have caller annotate the object (node v6.0.0, v8 5.0.71.35)
this._idleNext = null;
this._idlePrev = null;
this._callback = null;
this._argv = null;
this._onImmediate = null;
this.domain = process.domain;
}
exports.setImmediate = function(callback, arg1, arg2, arg3) {
if (typeof callback !== 'function') {
throw new TypeError('"callback" argument must be a function');
}
var i, args;
switch (arguments.length) {
// fast cases
case 1:
break;
case 2:
args = [arg1];
break;
case 3:
args = [arg1, arg2];
break;
default:
args = [arg1, arg2, arg3];
for (i = 4; i < arguments.length; i++)
// extend array dynamically, makes .apply run much faster in v6.0.0
args[i - 1] = arguments[i];
break;
}
return createImmediate(args, callback);
};
function createImmediate(args, callback) {
// declaring it `const immediate` causes v6.0.0 to deoptimize this function
var immediate = new Immediate();
immediate._callback = callback;
immediate._argv = args;
immediate._onImmediate = callback;
if (!process._needImmediateCallback) {
process._needImmediateCallback = true;
process._immediateCallback = processImmediate;
}
immediateQueue.append(immediate);
return immediate;
}
exports.clearImmediate = function(immediate) {
if (!immediate) return;
immediate._onImmediate = null;
immediateQueue.remove(immediate);
if (!immediateQueue.head) {
process._needImmediateCallback = false;
}
};
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