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async_hooks: add AsyncLocal class

Rodrigo Muino Tomonari requested to merge github/fork/Flarna/async_local into master

This introduces a new API to provide asynchronous storage via a new AsyncLocal class. Besides setting a value which is passed along asynchronous invocations it allows to register a callback to get informed about changes of the current value.

The implementation is based on async_hooks but it doesn't expose internals like execution Ids, resources or the hooks itself.

Naming and implementation is inspired by .NET AsyncLocal.

There is already #26540 adding similar functionality then this one and we should for sure not add both. I'm not sure if creating a new PR in parallel is the best way to discuss this but I think it's the easiest variant to allow anyone to give both a try.

Main differences between #26540 and this one:

  • #26540 follows trigger path of resources wheres this on follows execution path
  • This one has a copy on write semantic for the async value
  • This one allows to install a callback to get notified if value changes

As prove of concept I tried locally to port domains to use AsyncLocal instead async_hooks. I was able to get all tests green except 3 base on native addons using a domain property on the resource which seems to be deprecated meanwhile so I stopped there. The notification callback was needed to get this far.

Refs: https://docs.microsoft.com/en-us/dotnet/api/system.threading.asynclocal-1?view=netframework-4.7.2 Refs: #26540

fyi @nodejs/diagnostics @watson @vdeturckheim

Checklist
  • make -j4 test (UNIX), or vcbuild test (Windows) passes
  • tests and/or benchmarks are included
  • documentation is changed or added
  • commit message follows commit guidelines

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