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feat: use a symbol to store patched listeners #1356

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merged 8 commits into from
Aug 12, 2020
+12 −17
Merged

feat: use a symbol to store patched listeners #1356

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b106fb3
feat: use a symbol to store patched listeners
Flarna Jul 27, 2020
30b7bba
Merge branch 'master' into use-symbol
dyladan Aug 4, 2020
2705b98
Merge branch 'master' into use-symbol
Flarna Aug 4, 2020
452b7e7
Merge branch 'master' into use-symbol
Flarna Aug 7, 2020
677466f
Merge branch 'master' into use-symbol
Flarna Aug 10, 2020
1ef54c1
Merge branch 'master' into use-symbol
dyladan Aug 10, 2020
9bba484
Merge branch 'master' into use-symbol
dyladan Aug 11, 2020
1d91320
Merge branch 'master' into use-symbol
Flarna Aug 12, 2020
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29 changes: 12 additions & 17 deletions packages/opentelemetry-context-async-hooks/src/AbstractAsyncHooksContextManager.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@
import { ContextManager, Context } from '@opentelemetry/context-base';
import { EventEmitter } from 'events';

const kOtListeners = Symbol('OtListeners');

type Func<T> = (...args: unknown[]) => T;

type PatchedEventEmitter = {
Expand All @@ -25,7 +27,7 @@ type PatchedEventEmitter = {
* version so when the listener is removed by the user, we remove the
* corresponding "patched" function.
*/
__ot_listeners?: { [name: string]: WeakMap<Func<void>, Func<void>> };
[kOtListeners]?: { [name: string]: WeakMap<Func<void>, Func<void>> };
} & EventEmitter;

const ADD_LISTENER_METHODS = [
Expand Down Expand Up @@ -91,8 +93,8 @@ export abstract class AbstractAsyncHooksContextManager
context: Context
): T {
const ee = (target as unknown) as PatchedEventEmitter;
if (ee.__ot_listeners !== undefined) return target;
ee.__ot_listeners = {};
if (ee[kOtListeners] !== undefined) return target;
ee[kOtListeners] = {};

// patch methods that add a listener to propagate context
ADD_LISTENER_METHODS.forEach(methodName => {
Expand Down Expand Up @@ -124,13 +126,10 @@ export abstract class AbstractAsyncHooksContextManager
*/
private _patchRemoveListener(ee: PatchedEventEmitter, original: Function) {
return function (this: {}, event: string, listener: Func<void>) {
if (
ee.__ot_listeners === undefined ||
ee.__ot_listeners[event] === undefined
) {
const events = ee[kOtListeners]?.[event];
if (events === undefined) {
return original.call(this, event, listener);
}
const events = ee.__ot_listeners[event];
const patchedListener = events.get(listener);
return original.call(this, event, patchedListener || listener);
};
Expand All @@ -147,13 +146,9 @@ export abstract class AbstractAsyncHooksContextManager
original: Function
) {
return function (this: {}, event: string) {
if (
ee.__ot_listeners === undefined ||
ee.__ot_listeners[event] === undefined
) {
return original.call(this, event);
if (ee[kOtListeners]?.[event] !== undefined) {
delete ee[kOtListeners]![event];
}
delete ee.__ot_listeners[event];
return original.call(this, event);
};
}
Expand All @@ -172,11 +167,11 @@ export abstract class AbstractAsyncHooksContextManager
) {
const contextManager = this;
return function (this: {}, event: string, listener: Func<void>) {
if (ee.__ot_listeners === undefined) ee.__ot_listeners = {};
let listeners = ee.__ot_listeners[event];
if (ee[kOtListeners] === undefined) ee[kOtListeners] = {};
let listeners = ee[kOtListeners]![event];
if (listeners === undefined) {
listeners = new WeakMap();
ee.__ot_listeners[event] = listeners;
ee[kOtListeners]![event] = listeners;
}
const patchedListener = contextManager.bind(listener, context);
// store a weak reference of the user listener to ours
Expand Down