Allow Remote Config acknowledgements to be async

[watson]

Old API

Remote Config updates coming from the Agent needs to be acknowledged. Currently this is done synchronously in the Node.js tracer:

If a listener is attached to a given product, any config updates to that product is automatically acknowledged (if the listener doesn't throw, the state is set to ACKNOWLEDGED and if it throws, it's set to ERROR).

However, just because there's a listener and it doesn't throw, doesn't mean that the received config can be processed by the listener. It could be that the listener needs to do some async things before it can determine if the received config is valid.

New API

This PR changes the existing behavior by making the acknowledgement async: A 4th argument is emitted to listeners of rc.on(product) which is an ack callback which should be called once the listener wants to acknowledge the received config. It can optionally be called with an error object as its only argument to set the state to ERROR instead of ACKNOWLEDGED.

Update:

This PR changes the existing behavior by optionally allowing the acknowledgement to be async. This is achieved by:

• Changing the way you register products from using the EventEmitter API to a custom API that only allows a single handler per product (event emitters can have more than one listener, which is problematic as we can't support more than one of the listeners to acknowledge the config). The new API is as follows:
  • rc.setProductHandler(product, handler) (prevously rc.on(product, handler))
  • rc.removeProductHandler(product) (prevously rc.off(product, handler))
• The new product handler is called similar to the old event listener, with the following exception: A new optional 4th argument is supplied called ack. This is a callback which can be called (sync or async) either without any arguments (to set the state to ACKNOWLEDGED) or with a single error argument (to set the state to ERROR).
  • If the handler function signature takes less than 4 arguments or doesn't use the rest operator (...args), and...
    • ...the handler doesn't return a Promise: The state is set to ACKNOWLEDGED right away without the handler having to do anything (existing behavior)
    • ...the handler returns a Promise, we wait until the promise is resolved or rejected and set the state accordingly (new behavior)
  • If the handler function signature takes 4 or more arguments or use the rest operator (...args): The state is left as UNACKNOWLEDGED until the ack callback is called (new behavior)
  • In any case, the state is still set to ERROR if the handler throws (existing behavior)

The RemoteConfigManager is still an EventEmitter however because the kPreUpdate symbol is still being emitted. That part could do with a complete refactor, but is out of scope for this PR.

[watson]

• [DI] Add ability to take state snapshot #4549
• Prepare support for Dynamic Instrumentation #4492
• Allow Remote Config acknowledgements to be async #4638 👈
• master

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[github-actions]

Overall package size

Self size: 7.04 MB
Deduped: 62.41 MB
No deduping: 62.69 MB

Dependency sizes

| name | version | self size | total size | |------|---------|-----------|------------| | @datadog/native-appsec | 8.1.1 | 18.67 MB | 18.68 MB | | @datadog/native-iast-taint-tracking | 3.1.0 | 12.27 MB | 12.28 MB | | @datadog/pprof | 5.3.0 | 9.85 MB | 10.22 MB | | protobufjs | 7.2.5 | 2.77 MB | 5.16 MB | | @datadog/native-iast-rewriter | 2.4.1 | 2.14 MB | 2.23 MB | | @opentelemetry/core | 1.14.0 | 872.87 kB | 1.47 MB | | @datadog/native-metrics | 2.0.0 | 898.77 kB | 1.3 MB | | @opentelemetry/api | 1.8.0 | 1.21 MB | 1.21 MB | | jsonpath-plus | 9.0.0 | 580.4 kB | 1.03 MB | | import-in-the-middle | 1.8.1 | 71.67 kB | 785.15 kB | | msgpack-lite | 0.1.26 | 201.16 kB | 281.59 kB | | opentracing | 0.14.7 | 194.81 kB | 194.81 kB | | pprof-format | 2.1.0 | 111.69 kB | 111.69 kB | | @datadog/sketches-js | 2.1.0 | 109.9 kB | 109.9 kB | | semver | 7.6.3 | 95.82 kB | 95.82 kB | | lodash.sortby | 4.7.0 | 75.76 kB | 75.76 kB | | lru-cache | 7.14.0 | 74.95 kB | 74.95 kB | | ignore | 5.3.1 | 51.46 kB | 51.46 kB | | int64-buffer | 0.1.10 | 49.18 kB | 49.18 kB | | shell-quote | 1.8.1 | 44.96 kB | 44.96 kB | | istanbul-lib-coverage | 3.2.0 | 29.34 kB | 29.34 kB | | rfdc | 1.3.1 | 25.21 kB | 25.21 kB | | tlhunter-sorted-set | 0.1.0 | 24.94 kB | 24.94 kB | | limiter | 1.1.5 | 23.17 kB | 23.17 kB | | dc-polyfill | 0.1.4 | 23.1 kB | 23.1 kB | | retry | 0.13.1 | 18.85 kB | 18.85 kB | | jest-docblock | 29.7.0 | 8.99 kB | 12.76 kB | | crypto-randomuuid | 1.0.0 | 11.18 kB | 11.18 kB | | path-to-regexp | 0.1.7 | 6.78 kB | 6.78 kB | | koalas | 1.0.2 | 6.47 kB | 6.47 kB | | module-details-from-path | 1.0.3 | 4.47 kB | 4.47 kB |

_{🤖 This report was automatically generated by heaviest-objects-in-the-universe}

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-09-04 11:05:41

Comparing candidate commit ce21573 in PR branch watson/DEBUG-2532/rc-async with baseline commit 4b565ac in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 260 metrics, 6 unstable metrics.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.55%. Comparing base (c8e6070) to head (502ac79).
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4638      +/-   ##
==========================================
+ Coverage   69.19%   77.55%   +8.35%     
==========================================
  Files           1       13      +12     
  Lines         198      980     +782     
  Branches       33       33              
==========================================
+ Hits          137      760     +623     
- Misses         61      220     +159     

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