FFL-1273 Native feature flags evaluation #5054

dd-oleksii · 2025-11-17T20:09:01Z

What does this PR do?

Implement OpenFeature evaluator using bindings to native libdatadog evaluator.

Change log entry

Additional Notes:

How to test the change?

github-actions · 2025-11-17T20:09:20Z

👋 Hey @p-datadog, please fill "Change log entry" section in the pull request description.

If changes need to be present in CHANGELOG.md you can state it this way

**Change log entry**

Yes. A brief summary to be placed into the CHANGELOG.md

(possible answers Yes/Yep/Yeah)

Or you can opt out like that

**Change log entry**

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^{Visited at: 2025-11-18 22:25:28 UTC}

ext/libdatadog_api/feature_flags.c

datadog-datadog-prod-us1 · 2025-11-17T20:30:08Z

✅ Tests

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

🎯 Code Coverage
• Patch Coverage: 96.99%
• Total Coverage: 95.21% (+0.04%)

View detailed report

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 1ae3feb | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

ext/libdatadog_api/feature_flags.c

pr-commenter · 2025-11-19T15:56:54Z

Benchmarks

Benchmark execution time: 2025-11-27 17:42:16

Comparing candidate commit 1ae3feb in PR branch FFL-1273-native-feature-flags-evaluation with baseline commit 92d6689 in branch master.

Found 1 performance improvements and 1 performance regressions! Performance is the same for 42 metrics, 2 unstable metrics.

scenario:profiling - intern mixed existing and new

🟩 throughput [+1.662op/s; +2.882op/s] or [+5.861%; +10.163%]

scenario:profiling - intern_all 1000 repeated strings

🟥 throughput [-3156.113op/s; -3083.383op/s] or [-12.144%; -11.864%]

github-actions · 2025-11-19T19:31:04Z

Typing analysis

Note: Ignored files are excluded from the next sections.

Untyped methods

This PR introduces 3 untyped methods and 1 partially typed method. It increases the percentage of typed methods from 54.99% to 55.21% (+0.22%).

Untyped methods (+3-0)

❌ Introduced:

sig/datadog/core/feature_flags.rbs:22
└── def raw_value: () -> untyped
sig/datadog/core/feature_flags.rbs:24
└── def value: () -> untyped
sig/datadog/core/feature_flags.rbs:26
└── def value=: (untyped) -> untyped

Partially typed methods (+1-0)

❌ Introduced:

sig/datadog/core/feature_flags.rbs:46
└── def json?: (untyped) -> bool

If you believe a method or an attribute is rightfully untyped or partially typed, you can add # untyped:accept to the end of the line to remove it from the stats.

This commit is recovering Sameeran's work from #5034

Co-authored-by: Leo Romanovsky <[email protected]>

ext/libdatadog_api/feature_flags.c

Strech · 2025-11-20T12:42:41Z

@codex review

lib/datadog/open_feature/native_evaluator.rb

sig/datadog/core/feature_flags.rbs

ext/libdatadog_api/feature_flags.c

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ext/libdatadog_api/feature_flags.c

Strech

Left a super-small correction of comment. I think we are good to go as soon as we get 👍🏼 from the perf team

ivoanjo

I'm a bit short on time today so I gave a pass only on the feature_flags.c file -- that part LGTM (after a final suggested fix)

ext/libdatadog_api/feature_flags.c

y9v

left some non-blocking comments

lib/datadog/core/feature_flags.rb

lib/datadog/open_feature/native_evaluator.rb

lib/datadog/core/feature_flags.rb

lib/datadog/open_feature/provider.rb

dd-oleksii · 2025-11-25T18:10:34Z

/merge

dd-devflow-routing-codex · 2025-11-25T18:10:38Z

View all feedbacks in Devflow UI.

2025-11-25 18:10:37 UTC ℹ️ Start processing command /merge

2025-11-25 18:10:52 UTC ℹ️ MergeQueue: waiting for PR to be ready

This pull request is not mergeable according to GitHub. Common reasons include pending required checks, missing approvals, or merge conflicts — but it could also be blocked by other repository rules or settings.
It will be added to the queue as soon as checks pass and/or get approvals.
Note: if you pushed new commits since the last approval, you may need additional approval.
You can remove it from the waiting list with /remove command.

2025-11-25 22:11:12 UTC ⚠️ MergeQueue: This merge request was unqueued

devflow unqueued this merge request: It did not become mergeable within the expected time

lib/datadog/core/feature_flags.rb

lib/datadog/open_feature/evaluation_engine.rb

lib/datadog/open_feature/native_evaluator.rb

lib/datadog/open_feature/provider.rb

p-datadog · 2025-11-26T00:01:07Z

ext/libdatadog_api/feature_flags.c

+
+// Forward declarations
+static VALUE configuration_new(VALUE klass, VALUE json_str);
+static void configuration_free(void *ptr);


Is this function taking a configuration as a parameter? If yes configuration would be a better name for the argument, void * already indicates it's a pointer.

Yes and no. ptr is a data portion of RTypedData. It happens to be ddog_ffe_Handle_Configuration right now, so it's technically a configuration but not the one exposed to Ruby.

Note that this function is not exposed to Ruby, it's a part of integration with GC

p-datadog · 2025-11-26T00:03:51Z

ext/libdatadog_api/feature_flags.c

+  VALUE feature_flags_module = rb_define_module_under(core_module, "FeatureFlags");
+
+  rb_gc_register_address(&feature_flags_error_class);
+  feature_flags_error_class = rb_define_class_under(feature_flags_module, "Error", rb_eStandardError);


This class is also defined in Ruby code, what is the purpose of having two definitions?

We need one here so we can refer to it later. I think we can remove the one defined in Ruby, although it would make the code confusing.

cc @Strech for your opinion

(For what it's worth, I like keeping the definitions on the Ruby side too, as a lot of tools gets confusing with the Ruby -> C transition and so it's clearer to have something on the Ruby side even though it gets used from C.)

(Instead of defining a class, it's possible to read from the constant instead, but the amount of code is similar so I'd keep it as-is)

dd-oleksii · 2025-11-26T15:03:42Z

@p-datadog I'll work on addressing the comments but could you please clarify what comments are actually blocking the merge?

ext/libdatadog_api/feature_flags.c

p-datadog · 2025-11-26T18:09:34Z

ext/libdatadog_api/feature_flags.c

+      break;
+    default:
+      // Skip unsupported attribute types.
+      return ST_CONTINUE;


Is there an exception guard around the entire feature? If so, would it make sense to raise an exception here instead of silently ignoring unhandled input?

Yes, there is a guard. No, it doesn't make sense because we can continue and produce results in most cases.

ext/libdatadog_api/feature_flags.c

lib/datadog/core/feature_flags.rb

Co-authored-by: Oleg Pudeyev <[email protected]>

* Add comments about reconfiguration argument and methods

Strech reviewed Nov 17, 2025

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dd-oleksii force-pushed the FFL-1273-native-feature-flags-evaluation branch 3 times, most recently from 90dd290 to df67799 Compare November 18, 2025 20:21

dd-oleksii changed the base branch from master to oleksii/libdatadog-24.0.1 November 18, 2025 20:22

Base automatically changed from oleksii/libdatadog-24.0.1 to master November 18, 2025 22:25

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dd-oleksii force-pushed the FFL-1273-native-feature-flags-evaluation branch from ccef8cc to a6db269 Compare November 19, 2025 19:41

github-actions bot added the core Involves Datadog core libraries label Nov 19, 2025

FFL-1273 C binding for feature flag evaluation

46baabd

This commit is recovering Sameeran's work from #5034

dd-oleksii force-pushed the FFL-1273-native-feature-flags-evaluation branch from a6db269 to 106a374 Compare November 19, 2025 19:42

FFL-1273 Feature flags extension module

bbf5bc4

Co-authored-by: Leo Romanovsky <[email protected]>

dd-oleksii force-pushed the FFL-1273-native-feature-flags-evaluation branch from 106a374 to 4862383 Compare November 19, 2025 19:49

dd-oleksii commented Nov 19, 2025

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dd-oleksii requested review from a team as code owners November 21, 2025 11:44

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Strech approved these changes Nov 21, 2025

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dd-oleksii added 2 commits November 21, 2025 14:21

fix comment typo

379e9eb

chore: expand TODO note referencing FFL-1450

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ivoanjo approved these changes Nov 21, 2025

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fix: register gc address before assignment

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dd-oleksii force-pushed the FFL-1273-native-feature-flags-evaluation branch 3 times, most recently from 3171bd5 to 74a8452 Compare November 25, 2025 15:04

Return GENERAL error_code instead of PROVIDER_FATAL by default

262cd28

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Strech and others added 4 commits November 27, 2025 12:23

Add comments for some methods and private APIs

0493802

Update lib/datadog/core/feature_flags.rb

b894158

Co-authored-by: Oleg Pudeyev <[email protected]>

Change methods signatures based on the feedback

f77fb61

* Add comments about reconfiguration argument and methods

raise exceptions in cases that should never happen

1ae3feb

dd-oleksii requested a review from p-datadog November 27, 2025 18:09

FFL-1273 Native feature flags evaluation #5054

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FFL-1273 Native feature flags evaluation #5054

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Benchmarks

scenario:profiling - intern mixed existing and new

scenario:profiling - intern_all 1000 repeated strings

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Typing analysis

Untyped methods

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