support async hooks

[achille-roussel]

In places where we use async_hooks, the propagation of the async execution context stops when async functions returning thenable objects are called. This is because the async function will chain the call to the thenable, but it happens asynchronously on the process' next tick, which is outside the scope of the async execution context that originally called the function.

The superagent request objects we use in integrations are thenable, which exposes them to this issue. This means that we cannot use async local storage to propagate values from the incoming to outgoing requests.

Full details on the topic can be found in nodejs/node#22360

This PR addresses the issue by explicitly creating an async resource for each request that the integration creates, capturing the current execution context, and restoring it when the then method is eventually called.

[pelletier]

Props on digging that up!

[mericsson]

Interesting. Is the current implementation different than:

Suggested change

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

[achille-roussel]

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

[mericsson]

Interesting thanks!

[mericsson]

Very interesting. I'm not familiar with async_hooks but this lgtm.

7.1.0 package semver is good too.

you can merge and then npm publish.

then please yarn install @segment/[email protected] --exact in analytics-cloud-integrations and integrations.

[achille-roussel]

Thank you all for the reviews!