Add FFE evaluation metrics#3911
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Benchmarks [ tracer ]Benchmark execution time: 2026-05-27 02:29:23 Comparing candidate commit a04bdda in PR branch Found 0 performance improvements and 5 performance regressions! Performance is the same for 189 metrics, 0 unstable metrics. scenario:MessagePackSerializationBench/benchMessagePackSerialization-opcache
scenario:PDOBench/benchPDOOverhead
scenario:PDOBench/benchPDOOverheadWithDBM
scenario:TraceSerializationBench/benchSerializeTrace
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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().
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Adds a parallel pathway for PHP feature-flag evaluation metrics mirroring the FfeExposures forwarder. dd-trace-php encodes `feature_flag.evaluations` counters as OTLP/protobuf in PHP (via its existing PHP 7-safe `OtlpMetricEncoder`) and ships the encoded bytes to the sidecar, which POSTs them to the user-configured OTLP HTTP metrics intake. Why a sibling action instead of reusing FfeExposures: - The OTLP collector is not the Datadog Agent. It's user-configurable via OTEL_EXPORTER_OTLP_METRICS_ENDPOINT (default http://localhost:4318/v1/metrics), so the endpoint travels with the payload rather than being derived from the sidecar session's agent base URL. - Content type differs (application/x-protobuf vs application/json). - No EVP subdomain header. - The payload is binary protobuf, not a JSON string. dd-trace-php side (PR DataDog/dd-trace-php#3911) will refactor its existing `OtlpHttpMetricTransport` (which currently does PHP-side HTTP I/O, violating the architectural rule "no I/O outside the sidecar") to call this new FFI. Validation: - `cargo test -p datadog-sidecar ffe` passes 7 tests (3 exposures + 4 metrics). - `cargo check -p datadog-sidecar-ffi` clean.
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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Per Bob's PR review (2026-05-22), the tracer extension must perform no I/O outside the sidecar. Replaces the raw-socket `AgentExposureTransport` with `SidecarExposureTransport`, which forwards exposure batches to the libdatadog sidecar via a new native PHP function `\DDTrace\send_ffe_exposures` that calls the `ddog_sidecar_send_ffe_exposures` FFI added in DataDog/libdatadog#2026. PHP side: - Delete `Internal/Exposure/AgentExposureTransport.php` (raw socket POST to the Agent EVP proxy). - Add `Internal/Exposure/SidecarExposureTransport.php` that JSON-encodes the batch and calls `\DDTrace\send_ffe_exposures()`. Fire-and-forget; the sidecar handles retries. - Update `ExposureWriter::createDefault()` to instantiate the sidecar transport. - Drop the obsolete `testAgentTransportBuildsAgentEvpRequest` PHPUnit test (HTTP construction now lives in libdatadog, covered by `cargo test -p datadog-sidecar ffe_flusher`). - Add `Internal/DefaultEvaluationCompletedHook` and `Internal/CompositeEvaluationCompletedHook` so production callers go through a composite hook factory. In this PR the composite contains only `ExposureHook`; the metrics PR (#3911) contributes `EvaluationMetricHook` and the file conflict at merge resolves by combining both. Update `Client::create()` to call `DefaultEvaluationCompletedHook::create()`. C/Rust bridge: - Declare `ddog_ByteSlice` (and underlying `ddog_Slice_U8`) in `components-rs/common.h` for the metrics path; declare both `ddog_sidecar_send_ffe_exposures` and `ddog_sidecar_send_ffe_metrics` in `components-rs/sidecar.h`. - Add C wrappers `ddtrace_sidecar_send_ffe_exposures(zend_string *)` and `ddtrace_sidecar_send_ffe_metrics(zend_string *endpoint, zend_string *payload_bytes)` in `ext/sidecar.{h,c}` that call the FFI with the current sidecar transport + instance id + queue id. - Declare native PHP functions `\DDTrace\send_ffe_exposures(string): bool` and `\DDTrace\send_ffe_metrics(string, string): bool` in `ext/ddtrace.stub.php`; add corresponding arginfo entries and `ZEND_FUNCTION` registrations in `ext/ddtrace_arginfo.h`; implement `PHP_FUNCTION(DDTrace_send_ffe_exposures)` and `PHP_FUNCTION(DDTrace_send_ffe_metrics)` in `ext/ddtrace.c`. - Bump `libdatadog` submodule to FFE branch tip `29762335c` (which provides both FFIs). The submodule will be bumped to the libdatadog main commit once #2026 merges. Docs: - Add `docs/php-ffe-stack/{stack,system}-pr3910.{mmd,png}` for this PR. Validation: - `php vendor/bin/phpunit --config phpunit.xml tests/api/Unit/FeatureFlags` → 41 tests, 174 assertions, OK. - libdatadog sidecar tests (`cargo test -p datadog-sidecar ffe_flusher`) → 3 passed, on the pinned submodule commit. - Mermaid PNGs regenerate via `npx @mermaid-js/mermaid-cli`. `make test_featureflags` and `make test_c TESTS=tests/ext/ffe/...` will run in CI; running them locally requires rebuilding the extension which is gated behind libdatadog #2026 merging.
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.
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The SidecarOtlpMetricsTransport::resolveEndpoint() default ("http://localhost:4318/v1/metrics")
doesn't match the system-tests parametric setup, where the PHP test
client receives DD_AGENT_HOST=<test_agent_container> but no
OTEL_EXPORTER_OTLP_METRICS_ENDPOINT. The previous OtlpHttpMetricTransport
(replaced by this transport) derived the OTLP endpoint from DD_AGENT_HOST
+ port 4318. Restore that fallback so system-tests
test_php_ffe_evaluation_metric finds the test-agent OTLP intake.
Resolution order (now matches the old transport):
1. OTEL_EXPORTER_OTLP_METRICS_ENDPOINT (explicit)
2. OTEL_EXPORTER_OTLP_ENDPOINT + /v1/metrics
3. DD_AGENT_HOST + :4318/v1/metrics
4. localhost:4318/v1/metrics
The C/Rust bridge for the new native PHP functions \DDTrace\send_ffe_exposures() and \DDTrace\send_ffe_metrics() lives on the M2 EVP exposures PR (#3910) because that PR introduced the bridge when refactoring the exposure transport. PR #3911 (this PR) needs the same bridge for its OTLP metrics transport — without it the SidecarOtlpMetricsTransport silently drops batches because function_exists('\\DDTrace\\send_ffe_metrics') is false. Adds the same bridge files here so the M3 branch is independently compilable. At merge time the two PRs will conflict at the file level on these bridge files; resolution is deduplication (the bridge is identical in both PRs by design). Files added/modified: - components-rs/sidecar.h: declares ddog_sidecar_send_ffe_exposures and ddog_sidecar_send_ffe_metrics FFIs. - components-rs/common.h: declares ddog_ByteSlice typedef for the metrics payload. - ext/sidecar.h, ext/sidecar.c: C wrappers ddtrace_sidecar_send_ffe_exposures() and ddtrace_sidecar_send_ffe_metrics(). - ext/ddtrace.stub.php, ext/ddtrace_arginfo.h, ext/ddtrace.c: declares the native PHP functions and the PHP_FUNCTION implementations.
Pulls in libdatadog commit `875ec8f0e` ("fix(sidecar): dispatch FFE
actions before application-entry check"). Without this fix, the
`SidecarOtlpMetricsTransport::send()` call from PHP would silently
no-op for short-lived processes: the sidecar received the
`FfeMetrics` action but dropped it because the `Entry::Occupied`
gate on the application metadata had not yet fired.
This unblocks the parametric system-test
`Test_Feature_Flag_Parametric_Evaluation_Metrics::test_php_ffe_evaluation_metric`
which exercises the full PHP -> sidecar -> OTLP-HTTP-intake path
end-to-end. Local result: 26/27 FFE-scoped parametric tests pass
(remaining failure is the EVP exposure test, which lives on the
M2 PR #3910 branch).
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Pulls in libdatadog commit `875ec8f0e` ("fix(sidecar): dispatch FFE
actions before application-entry check") so the EVP exposure batch sent
via `ddog_sidecar_send_ffe_exposures` is no longer silently dropped
when the PHP runtime hasn't yet registered the application against the
sidecar's `QueueId`. Same fix is on the sibling PR #3911 (`2a48c4987")
for the OTLP metric path.
Without this submodule bump, `Test_Feature_Flag_Parametric_Exposures::test_php_ffe_exposure_event`
sees zero EVP POSTs at the test-agent because the sidecar's
`enqueue_actions` handler discards the `FfeExposures` action under
the `Entry::Occupied` gate.
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…macOS+colima
`build-debug-artifact` produces a `/output` bind mount via `-v
${TMP_OUT}:/output`. On macOS+colima only paths under $HOME are
mounted into the Linux VM; the macOS default `/var/folders/...` temp
dir is not, so writes from inside the container to `/output` land in
the VM and never propagate back to the host. The script exits without
error and the user's binaries dir is left with whatever stale artifact
was there before.
Pin TMP_OUT/TMP_PKG under $OUTPUT_DIR (which the user just passed as
an absolute, usable destination) so the bind mount is always on a
host-visible path. Inherits cleanup via the existing EXIT trap.
The same fix is independently on the M3 branch (#3911) as part of
e74b050; bringing it to the M2 branch (#3910) so both branches are
buildable on macOS without a `TMPDIR=$HOME/...` override.
…gh rez Three fixes to the per-PR FFE diagrams: 1. **Titles were truncated to "PHP FFE 4-PR stack — current =" with the PR number missing.** Mermaid uses the YAML frontmatter for the title block, and YAML treats unquoted `#` as the start of a comment, so `title: PHP FFE 4-PR stack — current = #3911 (OTLP metrics)` got parsed as just `PHP FFE 4-PR stack — current =`. Quoting the title keeps the `#PR-number` portion intact. 2. **System diagrams switched from `flowchart LR` to `flowchart TD`.** LR forced the PHP-process / host / backend lanes into a single very-wide row that rendered as an unreadable horizontal strip on PR pages. TD stacks them vertically and keeps the per-lane subgraphs readable. 3. **Re-rendered at 2400×2400 with `--scale 3`** (~1800×2000 stack, ~3000×4500 system) instead of the default ~600px width. PR-page thumbnails render legibly and zoomed-in detail stays sharp. README's regeneration recipe updated with all three knobs and a note on why the `title:` quoting matters.
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…gh rez Same three fixes as the parallel commit on the M3 (PR #3911) branch: 1. Quote the YAML `title:` so the `#PR-number` is not parsed as a comment (previous render had the title truncated at "current ="). 2. `flowchart LR` → `flowchart TD` on system diagrams so vertical PHP-process → host → backend lanes stack vertically instead of getting squeezed into one wide row. 3. Render with `-w 2400 -H 2400 --scale 3 -b white` (~1900×2000 stack, ~3000×4600 system) instead of ~600px default.
…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.
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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`.
…-ffe-evaluation-metrics
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| return rtrim($baseEndpoint, '/') . '/v1/metrics'; | ||
| } | ||
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| return 'http://localhost:4318/v1/metrics'; |
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When DD_METRICS_OTEL_ENABLED is used with the usual Datadog agent config (DD_AGENT_HOST or DD_TRACE_AGENT_URL) but no explicit OTEL_EXPORTER_OTLP*_ENDPOINT, this hardcoded localhost fallback sends FFE metrics to the application container instead of the agent. The existing OTel resolver in src/DDTrace/OpenTelemetry/CompositeResolver.php derives metrics endpoints from those Datadog settings, so in containerized deployments where DD_AGENT_HOST=datadog-agent makes normal OTel metrics work, these new feature_flag.evaluations batches are posted to localhost:4318 and get dropped.
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Motivation
PHP FFE evaluation metrics need to follow the native runtime architecture from the shared design doc: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0
PR 3906 gives PHP a real Remote Config-backed evaluator. This PR adds metric delivery without PHP OTLP writer, encoder, or transport code. The goal is for PHP to record one typed final evaluation result and have native/libdatadog sidecar code own buffering, aggregation, encoding, and OTLP submission.
Changes
This PR is stacked on #3906 and points the
libdatadogsubmodule at DataDog/libdatadog#2052 (1f1fca439), which is metric-only. NativeDDTrace\ffe_evaluaterecords evaluation metrics by default; the PHP 8 OpenFeature path disables that automatic native recording for the raw evaluation call and then records the final OpenFeature-aware outcome once through the typedEvaluationMetricRecorderadapter.The result FFI shape was also simplified per review feedback: Rust now exposes nullable raw
zend_string*pointers forFfeResultstrings instead of cbindgen-taggedOption<OwnedZendString>fields. C can move those strings directly into PHP result properties and metric recording without the extra result accessor/cleanup machinery.Decisions
Metric delivery remains separate from exposure logging. This PR intentionally expects OTLP evaluation metrics and no EVP exposure stream; #3910 owns exposure delivery and DataDog/libdatadog#2026 owns the exposure-only sidecar work.
The PHP layer is a typed adapter only. It does not aggregate metrics, encode OTLP, or submit HTTP payloads.
Validation
Focused PHP tests:
Result: 2 passed, 0 failed. The explicit
codesignstep works around a local macOSCODESIGNING / Invalid Pageload failure on the freshly linked local artifact; Linux/docker builds were not affected.Local ffe-dogfooding, PHP containers mounted from this branch, subject
php-3911-split-1779981881, 3 requests per PHP service:System-tests local validation, with PHP 8.0 NTS artifact rebuilt from commit
287184e2bandapache-mod-8.0rebuilt:cd /Users/leo.romanovsky/go/src/github.com/DataDog/system-tests-pr-g-php-ffe-scaffold TEST_LIBRARY=php ./run.sh FEATURE_FLAGGING_AND_EXPERIMENTATION tests/ffe/test_flag_eval_metrics.py -vvResult: 17 passed in 81.26 seconds.
Related PRs: #3906, DataDog/libdatadog#2052, DataDog/system-tests#7033.