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support async hooks #88

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merged 3 commits into from
Jun 11, 2020
Merged

support async hooks #88

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ebd401a
support async hooks
Jun 11, 2020
b43a4f7
require async_hooks
Jun 11, 2020
6d8a3da
update version
Jun 11, 2020
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19 changes: 19 additions & 0 deletions src/proto.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
* Module dependencies.
*/

const { AsyncResource } = require('async_hooks')
var ResourceLockedError = require('./errors').ResourceLockedError
var ValidationError = require('./errors').Validation
var normalize = require('to-no-case')
Expand Down Expand Up @@ -242,6 +243,24 @@ exports.request = function (method, path) {
return fn(err, res)
}

// Captures the current async context by creating an async resource for the
// superagent request.
//
// This is necessary because async_hooks does not follow "Thenable" types,
// depsite promises being compatible with them. The "then" method is invoked
// asynchronously on a "nextTick", where the async context that originally
// created the "Thenable" object has been lost.
//
// By creating the async resource here and overriding the "then" method, we
// bind the request object to the async execution context, and can restore
// it via a call to runInAsyncScope in the overriden "then" function.
const asyncResource = new AsyncResource('com.segment.integration.Request')
const thenFunction = Reflect.get(req, 'then')
const thenAsyncHook = function then (resolve, reject) {
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Interesting. Is the current implementation different than:

Suggested change
const thenAsyncHook = function then (resolve, reject) {
function thenAsyncHook (resolve, reject) {

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I think in the current code the function will be named then, so it leaks less details about the hack we're doing.

const thenAsyncHook = function then () {}
console.log(thenAsyncHook.name)
console.log((function thenAsyncHook () {}).name)
$ node test.js
then
thenAsyncHook

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Interesting thanks!

return asyncResource.runInAsyncScope(thenFunction, this, resolve, reject)
}

req.then = thenAsyncHook
return req
}

Expand Down