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Stephen Belanger
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lib: rewrite AsyncLocalStorage without async_hooks
PR-URL: #48528 Reviewed-By: Matteo Collina <[email protected]> Reviewed-By: Yagiz Nizipli <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Benjamin Gruenbaum <[email protected]> Reviewed-By: Rafael Gonzaga <[email protected]> Reviewed-By: Chengzhong Wu <[email protected]> Reviewed-By: Santiago Gimeno <[email protected]> Reviewed-By: Gerhard Stöbich <[email protected]>
1 parent 0c1877a commit d1229ee

29 files changed

+658
-173
lines changed

‎benchmark/async_hooks/async-local-storage-getstore-nested-resources.js

+6-4
Original file line numberDiff line numberDiff line change
@@ -38,9 +38,11 @@ function runInAsyncScopes(resourceCount, cb, i = 0) {
3838

3939
function main({ n, resourceCount }) {
4040
const store = new AsyncLocalStorage();
41-
runInAsyncScopes(resourceCount, () => {
42-
bench.start();
43-
runBenchmark(store, n);
44-
bench.end(n);
41+
store.run({}, () => {
42+
runInAsyncScopes(resourceCount, () => {
43+
bench.start();
44+
runBenchmark(store, n);
45+
bench.end(n);
46+
});
4547
});
4648
}

‎benchmark/async_hooks/async-local-storage-getstore-nested-run.js

+3-3
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@ const { AsyncLocalStorage } = require('async_hooks');
1414
* - AsyncLocalStorage1.getStore()
1515
*/
1616
const bench = common.createBenchmark(main, {
17-
sotrageCount: [1, 10, 100],
17+
storageCount: [1, 10, 100],
1818
n: [1e4],
1919
});
2020

@@ -34,8 +34,8 @@ function runStores(stores, value, cb, idx = 0) {
3434
}
3535
}
3636

37-
function main({ n, sotrageCount }) {
38-
const stores = new Array(sotrageCount).fill(0).map(() => new AsyncLocalStorage());
37+
function main({ n, storageCount }) {
38+
const stores = new Array(storageCount).fill(0).map(() => new AsyncLocalStorage());
3939
const contextValue = {};
4040

4141
runStores(stores, contextValue, () => {

‎doc/api/cli.md

+16
Original file line numberDiff line numberDiff line change
@@ -886,6 +886,21 @@ and `"` are usable.
886886
It is possible to run code containing inline types by passing
887887
[`--experimental-strip-types`][].
888888

889+
### `--experimental-async-context-frame`
890+
891+
<!-- YAML
892+
added: REPLACEME
893+
-->
894+
895+
> Stability: 1 - Experimental
896+
897+
Enables the use of AsyncLocalStorage backed by AsyncContextFrame rather than
898+
the default implementation which relies on async\_hooks. This new model is
899+
implemented very differently and so could have differences in how context data
900+
flows within the application. As such, it is presently recommended to be sure
901+
your application behaviour is unaffected by this change before using it in
902+
production.
903+
889904
### `--experimental-default-type=type`
890905

891906
<!-- YAML
@@ -2893,6 +2908,7 @@ one is included in the list below.
28932908
* `--enable-network-family-autoselection`
28942909
* `--enable-source-maps`
28952910
* `--experimental-abortcontroller`
2911+
* `--experimental-async-context-frame`
28962912
* `--experimental-default-type`
28972913
* `--experimental-detect-module`
28982914
* `--experimental-eventsource`

‎lib/async_hooks.js

+14-105
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,6 @@ const {
1010
NumberIsSafeInteger,
1111
ObjectDefineProperties,
1212
ObjectFreeze,
13-
ObjectIs,
1413
ReflectApply,
1514
Symbol,
1615
} = primordials;
@@ -30,6 +29,8 @@ const {
3029
} = require('internal/validators');
3130
const internal_async_hooks = require('internal/async_hooks');
3231

32+
const AsyncContextFrame = require('internal/async_context_frame');
33+
3334
// Get functions
3435
// For userland AsyncResources, make sure to emit a destroy event when the
3536
// resource gets gced.
@@ -158,6 +159,7 @@ function createHook(fns) {
158159
// Embedder API //
159160

160161
const destroyedSymbol = Symbol('destroyed');
162+
const contextFrameSymbol = Symbol('context_frame');
161163

162164
class AsyncResource {
163165
constructor(type, opts = kEmptyObject) {
@@ -177,6 +179,8 @@ class AsyncResource {
177179
throw new ERR_INVALID_ASYNC_ID('triggerAsyncId', triggerAsyncId);
178180
}
179181

182+
this[contextFrameSymbol] = AsyncContextFrame.current();
183+
180184
const asyncId = newAsyncId();
181185
this[async_id_symbol] = asyncId;
182186
this[trigger_async_id_symbol] = triggerAsyncId;
@@ -201,12 +205,12 @@ class AsyncResource {
201205
const asyncId = this[async_id_symbol];
202206
emitBefore(asyncId, this[trigger_async_id_symbol], this);
203207

208+
const contextFrame = this[contextFrameSymbol];
209+
const prior = AsyncContextFrame.exchange(contextFrame);
204210
try {
205-
const ret =
206-
ReflectApply(fn, thisArg, args);
207-
208-
return ret;
211+
return ReflectApply(fn, thisArg, args);
209212
} finally {
213+
AsyncContextFrame.set(prior);
210214
if (hasAsyncIdStack())
211215
emitAfter(asyncId);
212216
}
@@ -270,110 +274,15 @@ class AsyncResource {
270274
}
271275
}
272276

273-
const storageList = [];
274-
const storageHook = createHook({
275-
init(asyncId, type, triggerAsyncId, resource) {
276-
const currentResource = executionAsyncResource();
277-
// Value of currentResource is always a non null object
278-
for (let i = 0; i < storageList.length; ++i) {
279-
storageList[i]._propagate(resource, currentResource, type);
280-
}
281-
},
282-
});
283-
284-
class AsyncLocalStorage {
285-
constructor() {
286-
this.kResourceStore = Symbol('kResourceStore');
287-
this.enabled = false;
288-
}
289-
290-
static bind(fn) {
291-
return AsyncResource.bind(fn);
292-
}
293-
294-
static snapshot() {
295-
return AsyncLocalStorage.bind((cb, ...args) => cb(...args));
296-
}
297-
298-
disable() {
299-
if (this.enabled) {
300-
this.enabled = false;
301-
// If this.enabled, the instance must be in storageList
302-
ArrayPrototypeSplice(storageList,
303-
ArrayPrototypeIndexOf(storageList, this), 1);
304-
if (storageList.length === 0) {
305-
storageHook.disable();
306-
}
307-
}
308-
}
309-
310-
_enable() {
311-
if (!this.enabled) {
312-
this.enabled = true;
313-
ArrayPrototypePush(storageList, this);
314-
storageHook.enable();
315-
}
316-
}
317-
318-
// Propagate the context from a parent resource to a child one
319-
_propagate(resource, triggerResource, type) {
320-
const store = triggerResource[this.kResourceStore];
321-
if (this.enabled) {
322-
resource[this.kResourceStore] = store;
323-
}
324-
}
325-
326-
enterWith(store) {
327-
this._enable();
328-
const resource = executionAsyncResource();
329-
resource[this.kResourceStore] = store;
330-
}
331-
332-
run(store, callback, ...args) {
333-
// Avoid creation of an AsyncResource if store is already active
334-
if (ObjectIs(store, this.getStore())) {
335-
return ReflectApply(callback, null, args);
336-
}
337-
338-
this._enable();
339-
340-
const resource = executionAsyncResource();
341-
const oldStore = resource[this.kResourceStore];
342-
343-
resource[this.kResourceStore] = store;
344-
345-
try {
346-
return ReflectApply(callback, null, args);
347-
} finally {
348-
resource[this.kResourceStore] = oldStore;
349-
}
350-
}
351-
352-
exit(callback, ...args) {
353-
if (!this.enabled) {
354-
return ReflectApply(callback, null, args);
355-
}
356-
this.disable();
357-
try {
358-
return ReflectApply(callback, null, args);
359-
} finally {
360-
this._enable();
361-
}
362-
}
363-
364-
getStore() {
365-
if (this.enabled) {
366-
const resource = executionAsyncResource();
367-
return resource[this.kResourceStore];
368-
}
369-
}
370-
}
371-
372277
// Placing all exports down here because the exported classes won't export
373278
// otherwise.
374279
module.exports = {
375280
// Public API
376-
AsyncLocalStorage,
281+
get AsyncLocalStorage() {
282+
return AsyncContextFrame.enabled ?
283+
require('internal/async_local_storage/native') :
284+
require('internal/async_local_storage/async_hooks');
285+
},
377286
createHook,
378287
executionAsyncId,
379288
triggerAsyncId,

‎lib/internal/async_context_frame.js

+50
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,50 @@
1+
'use strict';
2+
3+
const {
4+
getContinuationPreservedEmbedderData,
5+
setContinuationPreservedEmbedderData,
6+
} = internalBinding('async_context_frame');
7+
8+
let enabled_;
9+
10+
class AsyncContextFrame extends Map {
11+
constructor(store, data) {
12+
super(AsyncContextFrame.current());
13+
this.set(store, data);
14+
}
15+
16+
static get enabled() {
17+
enabled_ ??= require('internal/options')
18+
.getOptionValue('--experimental-async-context-frame');
19+
return enabled_;
20+
}
21+
22+
static current() {
23+
if (this.enabled) {
24+
return getContinuationPreservedEmbedderData();
25+
}
26+
}
27+
28+
static set(frame) {
29+
if (this.enabled) {
30+
setContinuationPreservedEmbedderData(frame);
31+
}
32+
}
33+
34+
static exchange(frame) {
35+
const prior = this.current();
36+
this.set(frame);
37+
return prior;
38+
}
39+
40+
static disable(store) {
41+
const frame = this.current();
42+
frame?.disable(store);
43+
}
44+
45+
disable(store) {
46+
this.delete(store);
47+
}
48+
}
49+
50+
module.exports = AsyncContextFrame;

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