[FFL-1284] Create datadog-ffe-ffi crate #1282
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BenchmarksComparisonBenchmark execution time: 2025-10-29 22:47:58 Comparing candidate commit 2d4e32d in PR branch Found 0 performance improvements and 0 performance regressions! Performance is the same for 55 metrics, 2 unstable metrics. CandidateCandidate benchmark detailsGroup 1
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Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #1282 +/- ##
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- Coverage 72.05% 71.96% -0.09%
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Files 368 371 +3
Lines 58076 58158 +82
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+ Hits 41847 41854 +7
- Misses 16229 16304 +75
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Artifact Size Benchmark Reportaarch64-alpine-linux-musl
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Creates C-compatible FFI layer for Feature Flagging & Experimentation: - Add datadog-ffe-ffi crate following ddsketch-ffi patterns - Implement Handle<T> wrappers for Configuration, EvaluationContext, Assignment - Export get_assignment, configuration_new, evaluation_context_new functions - Add memory management with drop functions - Generate C headers via cbindgen for Ruby integration - Update Cargo.toml to include new FFI crate in workspace
- Remove trailing whitespace from doc comments - Reformat function call in assignment.rs to fit line length constraints
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- Updated build.rs to use a variable for the header name and improved readability. - Modified cbindgen.toml to reorganize export settings and enforce naming conventions for types and functions. - Added Clippy lints in lib.rs to enhance code quality and prevent common pitfalls.
sameerank
commented
Oct 27, 2025
| [package] | ||
| name = "datadog-ffe-ffi" | ||
| edition.workspace = true | ||
| version = "0.1.0" |
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To match with
libdatadog/datadog-ffe/Cargo.toml
Line 3 in 7e0063f
to indicate that
datadog-ffe-ffi is not production ready
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I wonder if we can pin this, so that datadog-ffe and datadog-ffe-ffi versions are always aligned? Maybe we should put FFI functions into datadog-ffe directly
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I think this is a temporary issue. When FFI is ready, we can update datadog-ffe/Cargo.toml and datadog-ffe-ffi/Cargo.toml to
version.workspace = true # Would use "22.1.0"
From
Line 68 in a0e4bff
Also the version in the dependency should cause a build failure, which is another way of ensuring that they match
libdatadog/datadog-ffe-ffi/Cargo.toml
Line 24 in c453cb9
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No, we will not use the workspace version.
- It doesn't really suit us to have use the workspace version as it makes version bumps more complicated requiring cross-team alignment without any benefit
- libdatadog is migrating into the direction of each package having its own version
sameerank
commented
Oct 27, 2025
ekump
reviewed
Oct 28, 2025
dd-oleksii
reviewed
Oct 28, 2025
Pin datadog-ffe to exact version Co-authored-by: Oleksii Shmalko <[email protected]>
refactor(ffe): simplify error handling Merge branch 'sameerank/FFL-1284-Create-datadog-ffe-ffi-crate' into ffe-simplify-error-handling Co-authored-by: sameerank <[email protected]>
Replace ddog_ffe_evaluation_context_new_with_attribute with ddog_ffe_evaluation_context_new_with_attributes that accepts an array of AttributePair structs.
Handle take() errors gracefully in ddog_ffe_configuration_drop and ddog_ffe_assignment_drop to prevent malloc corruption from double-free or use-after-free scenarios. Previously, take() failures would panic and cause "pointer being freed was not allocated" errors.
- Changed the `context` parameter in `ddog_ffe_get_assignment` to be a pointer for consistency. - Removed the single-attribute constructor `ddog_ffe_evaluation_context_new` and updated the multi-attribute constructor's documentation for clarity.
dd-oleksii
reviewed
Nov 3, 2025
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| let config = config.to_inner_mut()?; | ||
| let context = context.to_inner_mut()?; |
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minor (postpone for now): .to_inner_mut() is creating &mut references which is unsound/unsafe with multi-threading. We'll need to migrate to using const-references in the future
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| let assignment_result = get_assignment(Some(config), flag_key, context, None, now())?; | ||
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| let handle = if let Some(assignment) = assignment_result { | ||
| Handle::from(assignment) | ||
| } else { | ||
| Handle::empty() | ||
| }; |
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major: ? is stripping all of the error details which are going to be important to populate reason/error_code/error_message openfeature fields. We need to return a new structure that would accurately preserve error codes, similarly to ResolutionDetails in DataDog/dd-trace-py#15098
| mut config: *mut Handle<Configuration>, | ||
| flag_key: *const c_char, | ||
| mut context: *mut Handle<EvaluationContext>, | ||
| ) -> Result<Handle<Assignment>> { |
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major(?): is Ruby able to access fields directly (I guess not?) or we need to provide accessor methods?
| targeting_key: *const c_char, | ||
| attributes: *const AttributePair, | ||
| attributes_count: usize, | ||
| ) -> Handle<EvaluationContext> { |
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minor: consider using similar error-handling pattern here
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| Str::from(name_str.to_string()), | ||
| Attribute::from(value_str.to_string()), |
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minor: this seems to do unnecessary allocation of String: CStr -> &str -> String -> Str. We shall be able to go directly from &str to Str:
Suggested change
| Str::from(name_str.to_string()), | |
| Attribute::from(value_str.to_string()), | |
| Str::from(name_str), | |
| Attribute::from(value_str), |
| #[repr(C)] | ||
| pub struct AttributePair { | ||
| pub name: *const c_char, | ||
| pub value: *const c_char, |
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major: how does this work for numeric and boolean attributes?
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What does this PR do?
Adds a
datadog-ffe-fficrate, which provides a C FFI (Foreign Function Interface) bindings for thedatadog-ffe(Feature Flag Evaluation) library. This is to allowdd-trace-rbto interact with the feature flag evaluation engine through a C-compatible API.The crate exposes the following key components:
Motivation
The motivation for FFL-1284 is to enable non-Rust languages (PHP, Ruby, Python, etc.) to use the feature flag evaluator in
libdatadog, for consistent feature flag evaluation in SDKs across languages.Additional Notes
datadog-profiling-ffi,datadog-crashtracker-ffi)cbindgenfor automatic C generationstaticlib,cdylib)How to test the change?
cargo build -p datadog-ffe-fficargo build -p datadog-ffe-ffi --features cbindgen(Check that headers are generated intarget/include/)[FFL-1273] bindings for libdatadog datadog ffe api dd-trace-rb#5001[FFL-1273] bindings for ffe in openfeature provider dd-trace-rb#5007