Packaging async_hooks in wrangler

Developers Workers
1

I’m trying to use async_hooks in my worker code.
This is a node package so the build system does not know it by default.

I’ve added node_compat = true to wrangler.toml. I already had it there because of another package that I needed, and wrangler prompted me to add it.
Also tried adding --node-compat to wrangler publish. I think it’s the same as the toml config.

When I try to build I get a message
The package "async_hooks" wasn't found on the file system but is built into node. Are you trying to bundle for node? You can use "platform: 'node'" to do that, which will remove this error.

This seems like eshint’s message, not wrangler.

I saw this PR in workerd that was merged and was supposedly made it possible to use async_hooks in. I don’t know what’s the relation between workerd and cf workers. Is cf using workerd latest, or do they have their own version?

I believe the CF is using this rollup plugin to build with node compatibility. However, it is from 3 years ago and does not mention async_hooks in its supported packages list.

Another possible relevant PR is this one, which is still open.

Does anyone have any clue on how to enable this package?

2

It is.

Seems unlikely that a polyfill would ever get the functionality so waiting for it to be available in the Workers runtime appears to be the only bet.

Runtime releases are usually every 2 weeks, so latest changes in workerd take some time to be in the live runtime.

Notably, it’s not the entire async_hooks package.

  • The AsyncLocalStorage implementation provided by Workers intentionally omits support for the asyncLocalStorage.enterWith() and asyncLocalStorage.disable() methods.

  • Workers does not implement the full async_hooks API upon which Node.js’ implementation of AsyncLocalStorage is built.

  • Workers does not implement the ability to create an AsyncResource with an explicitly identified trigger context as allowed by Node.js. This means that a new AsyncResource will always be bound to the async context in which it was created.

3

Thanks, @KianNH
So if the above workerd was merged last week, it is expected to become available within a week or so?
This is great news.
I’m only using asyncLocalStorage.run() and asyncLocalStorage.getStore(), so I believe it should work.

I’ll check up again next week

Thanks!

4

Yesterday only I tested a pages functions application with asyncLocalStorage.enterWith() and asyncLocalStorage.getStore() and it is working fine without any issue.

I am starting wrangler dev server using following command -

wrangler pages dev --compatibility-date=2023-03-07 --compatibility-flag=nodejs_compat --port 8888 --proxy 30051 -- yarn preview