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async_hooks: AsyncLocalStorage to diagnostics_channel integration #45277

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Qard wants to merge 4 commits into from
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async_hooks: AsyncLocalStorage to diagnostics_channel integration #45277

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0438150
lib: add tracing channel to diagnostics_channel
Oct 9, 2022
f8605a6
diagnostics_channel: make tracing channels safer and support symbol n…
Nov 9, 2022
789d1e0
diagnostics_channel: Avoid wrapping with no subscribers
Nov 9, 2022
e72265b
async_hooks: AsyncLocalStorage to diagnostics_channel integration
Nov 2, 2022
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diagnostics_channel: make tracing channels safer and support symbol n… 
…ames
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Stephen Belanger
Stephen Belanger committed Nov 9, 2022
commit f8605a62b49003cc0bbe703361b848aa1ea4ddae
82 changes: 50 additions & 32 deletions lib/diagnostics_channel.js
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Original file line number Diff line number Diff line change
Expand Up @@ -30,13 +30,15 @@ class ActiveChannel {
subscribe(subscription) {
validateFunction(subscription, 'subscription');
ArrayPrototypePush(this._subscribers, subscription);
this._weak.incRef();
}

unsubscribe(subscription) {
const index = ArrayPrototypeIndexOf(this._subscribers, subscription);
if (index === -1) return false;

ArrayPrototypeSplice(this._subscribers, index, 1);
this._weak.decRef();

// When there are no more active subscribers, restore to fast prototype.
if (!this._subscribers.length) {
Expand Down Expand Up @@ -68,6 +70,7 @@ class ActiveChannel {
class Channel {
constructor(name) {
this._subscribers = undefined;
this._weak = undefined;
this.name = name;
}

Expand Down Expand Up @@ -107,24 +110,17 @@ function channel(name) {
}

channel = new Channel(name);
channels[name] = new WeakReference(channel);
channel._weak = new WeakReference(channel);
channels[name] = channel._weak;
return channel;
}

function subscribe(name, subscription) {
const chan = channel(name);
channels[name].incRef();
chan.subscribe(subscription);
return channel(name).subscribe(subscription);
}

function unsubscribe(name, subscription) {
const chan = channel(name);
if (!chan.unsubscribe(subscription)) {
return false;
}

channels[name].decRef();
return true;
return channel(name).unsubscribe(subscription);
}

function hasSubscribers(name) {
Expand All @@ -139,46 +135,54 @@ function hasSubscribers(name) {
}

class TracingChannel {
#channels;

constructor(name) {
this.name = name;
this.channels = {
start: channel(`${name}.start`),
end: channel(`${name}.end`),
asyncEnd: channel(`${name}.asyncEnd`),
error: channel(`${name}.error`)
this.#channels = {
start: new Channel(Symbol(`tracing.start`)),
end: new Channel(Symbol(`tracing.end`)),
asyncEnd: new Channel(Symbol(`tracing.asyncEnd`)),
error: new Channel(Symbol(`tracing.error`))
};
}

// Attach WeakReference to all the sub-channels so the liveness management
// in subscribe/unsubscribe keeps the TracingChannel the sub-channels are
// attached to alive.
set _weak(weak) {
for (const key in this.#channels) {
this.#channels[key]._weak = weak;
}
}

get hasSubscribers() {
const { channels } = this;
for (const key in channels) {
if (channels[key].hasSubscribers) return true;
for (const key in this.#channels) {
if (this.#channels[key].hasSubscribers) {
return true;
}
}
return false;
}

subscribe(handlers) {
let subscribed = true;
for (const key in handlers) {
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Outdated
if (!subscribe(`${this.name}.${key}`, handlers[key])) {
subscribed = false;
}
this.#channels[key]?.subscribe(handlers[key]);
}
return subscribed;
}

unsubscribe(handlers) {
let unsubscribed = true;
for (const key in handlers) {
if (!unsubscribe(`${this.name}.${key}`, handlers[key])) {
unsubscribed = false;
const channel = this.#channels[key];
if (!channel || !channel.unsubscribe(handlers[key])) {
return false;

@Flarna Flarna Nov 14, 2022

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Why end the loop just because there is maybe an extra key in the object?

}
}
return unsubscribed;
return true;
}

traceSync(fn, ctx = {}, thisArg, ...args) {
const { start, end, error } = this.channels;
const { start, end, error } = this.#channels;
start.publish(ctx);
try {
const result = ReflectApply(fn, thisArg, args);
Expand All @@ -194,7 +198,7 @@ class TracingChannel {
}

tracePromise(fn, ctx = {}, thisArg, ...args) {
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const { asyncEnd, start, end, error } = this.channels;
const { asyncEnd, start, end, error } = this.#channels;
start.publish(ctx);

const reject = (err) => {
Expand Down Expand Up @@ -223,7 +227,7 @@ class TracingChannel {
}

traceCallback(fn, position = 0, ctx = {}, thisArg, ...args) {
const { start, end, asyncEnd, error } = this.channels;
const { start, end, asyncEnd, error } = this.#channels;
start.publish(ctx);

function wrap(fn) {
Expand Down Expand Up @@ -258,8 +262,22 @@ class TracingChannel {
}
}

const tracingChannels = ObjectCreate(null);

function tracingChannel(name) {
return new TracingChannel(name);
let channel;
const ref = tracingChannels[name];
if (ref) channel = ref.get();
if (channel) return channel;

if (typeof name !== 'string' && typeof name !== 'symbol') {
throw new ERR_INVALID_ARG_TYPE('tracingChannel', ['string', 'symbol'], name);
}

channel = new TracingChannel(name);
channel._weak = new WeakReference(channel);

@Flarna Flarna Nov 14, 2022

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Suggested change
channel._weak = new WeakReference(channel);
channel._weak = tracingChannels[name] = new WeakReference(channel);

TracingChannel#_weak is a setter, there is no getter otherwise this is always undefined

tracingChannels[name] = channel._weak;
return channel;
}

module.exports = {
Expand Down