fix: datadog tracer scope

[ngraef]

📝 Description

• Support dd-trace's AsyncLocalStorage and AsyncResource scope manager implementations (introduced in v0.27.0 and v0.28.0) and clean up the AsyncHooks implementation.
• Fix activation of moleculer spans in dd-trace, allowing for propagation to external modules. This also allows for log injection to connect logs and traces.
• Allow moleculer to continue a trace that was started in an external module. For example, this will show the moleculer-web handler as a child span of the node http listener.

🎯 Relevant issues

Resolves #690
Resolves #889

💎 Type of change

• Bug fix (non-breaking change which fixes an issue)

🚦 How Has This Been Tested?

• Unit and integration tests added
• Tested an environment with 5 distributed services (each running in separate containers) sending traces to Datadog. The sample screenshots below show cross-service calls, custom spans in an action handler, and modules auto-instrumented by dd-trace (http-client, tcp, dns, fs, redis, postgres).

A simple call through moleculer-web to a remote action that makes some HTTP calls and interacts with a postgres database

A call that includes some nested remote action calls, one of which calls redis and returns an error

The same call as the previous example, but with a remote service subscribing to an event it emits

The initial call to a lazy-loaded module with a bunch of fs reads needed to require the library

An action handler with some custom spans via ctx.startSpan

🏁 Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have commented my code, particularly in hard-to-understand areas

[ngraef]

@icebob This is now ready for review when you have some time.

[icebob]

It's a breaking change in the protocol, so it can be merged only in 0.15 or it can't work with schema-based serializers.

[ngraef]

I don't need it to work with schema-based serializers at the moment. Will the serializer implementations safely ignore the new property if they don't support it? The tracing middleware handles an undefined traceID in the context.

[icebob]

please merge changes from the master, some test is not up-to-date.

[ngraef]

please merge changes from the master, some test is not up-to-date.

This branch was already rebased onto master. I've rebased again to pull in the latest typing fixes.

I believe the failing test is either an incorrect implementation in src/async-storage.js or an incorrect assumption in the test.

[icebob]

It's an old module, it is not used in the library anymore. But somehow this PR affects the async_hooks if the unit test failed, but in the master it doesn't.

[ngraef]

But somehow this PR affects the async_hooks if the unit test failed, but in the master it doesn't.

I looked into this a bit more. The failure might not occur on a development machine by running npm test because jest will spawn multiple workers by default, and the datadog and async-storage tests might not run in the same process. The failure can be reproduced more easily (depending on test execution order) by setting the jest option --maxWorkers=1. This is the value used by default in the 2-core GitHub Actions runners.

The tests on the master branch don't have promise execution tracking enabled because storage.enable() is never called, so the hook is never enabled. Therefore, the executionAsyncId is 0 in both then callbacks and the shared resource is retrieved.

moleculer/test/integration/async-storage.spec.js

Lines 15 to 26 in c25f647

	const storage = new AsyncStorage(broker);
	const context = { a: 5 };
	return Promise.resolve()
	.then(() => {
	storage.setSessionData(context);
	expect(storage.getSessionData()).toBe(context);
	})
	.then(() => {
	expect(storage.getSessionData()).toBe(context);
	});

However, this PR adds tests for dd-trace's various scope implementations, which enable promise execution tracking for the process. In that case, the async-storage test fails because the then callbacks have different executionAsyncIds, and context propagation from parent to child async resources doesn't occur because the hook in the AsyncStorage class is not enabled. Enabling it in the test with storage.enable() will still fail because the context propagation implementation is broken.

Regardless, I've pushed a change that cleans up the hooks used in dd-trace and restores the previous passing behavior for the async-storage test.

[icebob]

@ngraef I see, I don't forget it, but I'm hesitating because it contains a lot of changes affecting the tracer, context, and the communication protocol. I don't feel it can be merged into the 0.14, instead on the next 0.15.
In the new version I will drop the schema-based serializer, and I plan to add headers feature in the Context, to store any middleware-based or user-based information which is transferred to remote nodes without causing breaking change in the protocol.

[icebob]

what do you think about it? DataDog/dd-trace-js#1598