Add FFE evaluation completion hook#3909
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Benchmarks [ tracer ]Benchmark execution time: 2026-05-24 04:07:19 Comparing candidate commit 04adf69 in PR branch Found 0 performance improvements and 5 performance regressions! Performance is the same for 188 metrics, 1 unstable metrics. scenario:ContextPropagationBench/benchInject64Bit-opcache
scenario:MessagePackSerializationBench/benchMessagePackSerialization
scenario:MessagePackSerializationBench/benchMessagePackSerialization-opcache
scenario:PHPRedisBench/benchRedisOverhead
scenario:SpanBench/benchDatadogAPI
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The canonical fixture PHPT explicitly enumerates the FFE classes it requires before instantiating the Datadog FeatureFlags client. The shared evaluation-completed envelope/hook added on this branch made Client::createWithDependencies() reference NoopEvaluationCompletedHook, EvaluationCompletedHook, and EvaluationCompleted, but the test helper had not been updated, so the packaged/extension PHPT failed with "Class DDTrace\FeatureFlags\Internal\NoopEvaluationCompletedHook not found" before any fixture case ran. Add the three new files to require_feature_flag_api so the PHPT matches the runtime class graph used by Client::evaluate().
Adds Mermaid sources and rendered PNGs for the hook (this) PR plus a README documenting the regeneration workflow. - `docs/php-ffe-stack/stack-pr3909.mmd` + `.png` — 4-PR stack with this PR highlighted (M1 done; EVP and metrics as siblings to come). - `docs/php-ffe-stack/system-pr3909.mmd` + `.png` — target system architecture; this PR contributes the EvaluationCompletedHook + OpenFeature provider hook surface. All downstream nodes (writers, sidecar FFI, sidecar process, backends) marked future. - `docs/php-ffe-stack/README.md` — npx invocation for regenerating PNGs locally; PR-by-PR diagram table; architectural rule note. The architectural rule encoded in the system diagram (all I/O via the libdatadog sidecar) is the same rule Bob applied to PR #3910. See DataDog/libdatadog#2026 for the sidecar-side support.
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Adds the M3 evaluation-metrics layer on top of the hook PR (#3909) as a sibling of the EVP exposures PR (#3910). Records `feature_flag.evaluations` for both PHP 7 (DD Client hook) and PHP 8 (OpenFeature SDK hook); both paths share `EvaluationMetricHook::sharedWriter()` for unified aggregation. OTLP/protobuf payloads are encoded in PHP via the existing `OtlpMetricEncoder` and delivered to the user-configured OTLP HTTP metrics intake through the libdatadog sidecar (`ddog_sidecar_send_ffe_metrics` FFI added in DataDog/libdatadog#2026). This branch is force-pushed (user-authorized one-time exception to the no-force-push rule, 2026-05-23) to restructure history away from being linearly stacked on the M2 exposures PR (#3910). The PR now stacks directly on the hook PR (#3909) as a sibling of the EVP PR. PHP side: - Add `Internal/Metric/EvaluationMetricWriter` with bounded series aggregation, drop accounting, and shutdown flush. - Add `Internal/Metric/EvaluationMetricHook` (DD Client hook) and `OtlpMetricEncoder` (PHP 7-safe protobuf encoding). - Add `Internal/Metric/SidecarOtlpMetricsTransport` that calls `\DDTrace\send_ffe_metrics()` (FFI declared in #3910). Endpoint resolution: `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT`, falling back to `OTEL_EXPORTER_OTLP_ENDPOINT + /v1/metrics`, default `http://localhost:4318/v1/metrics`. - Add `DDTrace\OpenFeature\EvalMetricsHook` implementing `OpenFeature\interfaces\hooks\Hook` (after + error stages), registered on `DataDogProvider` via `setHooks()`. - `DataDogProvider` constructs its internal DD `Client` with `DefaultEvaluationCompletedHook::createWithoutMetric()` so the OpenFeature path records the metric via the OpenFeature hook (PR 3911 scope) and NOT via the DD Client hook — preventing double-counting. PHP 7 path keeps recording via the DD Client hook. - Add `Internal/CompositeEvaluationCompletedHook` and `Internal/DefaultEvaluationCompletedHook` (metric-only composite). This is the merge-conflict point with PR #3910's `[ExposureHook]` composite — second merge resolves by combining both hooks. - Update `Client::create()` to call `DefaultEvaluationCompletedHook::create()`. - Drop the obsolete `testOtlpTransportBuildsHttpProtobufRequest` PHPUnit test (HTTP construction now lives in libdatadog, covered by `cargo test -p datadog-sidecar ffe_metrics_flusher`). - Add `_files_openfeature.php` entry for `EvalMetricsHook.php`. C/Rust bridge: the `\DDTrace\send_ffe_metrics()` native function, its C wrapper `ddtrace_sidecar_send_ffe_metrics()`, and the `ddog_sidecar_send_ffe_metrics` FFI declaration in `components-rs/sidecar.h` were already added in #3910. This PR's branch picks up those changes once #3910 merges (or via the same libdatadog submodule pin during review). For development locally the libdatadog submodule is pinned to the FFE branch tip (`29762335c`). Docs: - Add `docs/php-ffe-stack/{stack,system}-pr3911.{mmd,png}` per the 4-PR documentation convention. Validation: - `php vendor/bin/phpunit --config phpunit.xml tests/api/Unit/FeatureFlags` → 40 tests, 160 assertions, OK. - Mermaid PNGs regenerate via `npx @mermaid-js/mermaid-cli`. `make test_featureflags`, OpenFeature PHPUnit, and ffe-dogfooding end-to-end validation will run in CI / are validated separately by FOLLOW-05 Steps 4–5.
…gh rez Same three fixes as on the M2 (#3910) and M3 (#3911) sibling branches: 1. Quote the YAML `title:` so the `#PR-number` survives parsing (otherwise YAML treats the `#` as a comment and the title renders as "PHP FFE 4-PR stack — current =" with the rest missing). 2. `flowchart LR` → `flowchart TD` on the system diagram so the PHP-process / host-sidecar / backend lanes stack vertically. 3. Render at 2400×2400 `--scale 3` instead of ~600px default.
leoromanovsky
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Brings the PHP FFE diagram convention to the M1 PR. Each subsequent PR in the stack (#3909, #3910, #3911) already carried its own stack + system diagram; #3906 was missing them. Mirrors the format used by the rest of the stack: - `stack-pr3906.mmd` — the 4-PR stack with #3906 badged as current and the downstream layers shown as "future". - `system-pr3906.mmd` — the target end-to-end architecture with M1's scope (UserCode, OpenFeature Client, DataDogProvider, DDTrace FeatureFlags Client, NativeEvaluator, Remote Config client) highlighted, and everything from the Hook layer onward dashed. All conventions match the other branches: quoted YAML titles (to keep `#PR-number` out of the YAML comment parser), `flowchart TD` orientation, rendered with `-w 2400 -H 2400 --scale 3 -b white`.
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Motivation
EVP exposure delivery and OTLP evaluation metrics both need the same internal post-evaluation signal. This PR adds that shared hook layer on top of the runtime evaluation work in #3906.
It does not add exposure transport, caching, batching, OpenFeature SDK hook behavior, or metric export behavior.
Planning/reference doc: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0
Decisions
Client::evaluate()producesEvaluationDetailsfor evaluated success/default/error results.createWithDependencies()only.DefaultEvaluationCompletedHook,CompositeEvaluationCompletedHook, and OpenFeature SDK hook behavior land with their first consumers in Add FFE exposure emission #3910 / Add FFE evaluation metrics #3911.Where this PR fits in the stack
This is the internal hook layer. Runtime evaluations (#3906) sit beneath it; EVP exposures (#3910) and OTLP metrics (#3911) are independent siblings directly on top of it.
Where this PR fits in the target system
This PR contributes only the internal DD Client post-evaluation envelope and callback point. Downstream writers, sidecar FFIs, libdatadog sidecar forwarding, and Agent / OTLP backends land in #3910 / #3911 / DataDog/libdatadog#2026.
Changes
EvaluationCompletedenvelope with flag key, value/default types, targeting context, result value, reason, variant, error fields, allocation key, anddoLog.EvaluationCompletedHookplus a no-op implementation.DDTrace\FeatureFlags\Client::evaluate()after evaluation details are produced.