Enable PHP FFE exposure system tests#7031
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## Motivation PHP FFE exposure delivery needs a native path with a cache that persists beyond a single PHP request/thread. The shared design doc is the cross-PR reference: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0 This PR is exposure-only. Metrics were split into #2052 so reviewers can evaluate exposure cache and delivery separately from OTLP evaluation metrics. ## Changes This adds caller-driven FFE exposure sidecar actions, exposure payload forwarding through the Agent EVP proxy, and a shared exposure cache that deduplicates repeated `(service, env, version, flag, subject)` assignments across PHP requests and sidecar connections. The reusable FFE-domain pieces now live in `datadog-ffe` behind the `exposure-events` feature: exposure input types, the LRU deduplication cache, and JSON payload encoding. `datadog-sidecar` keeps only sidecar-specific work: deriving the agent EVP endpoint, building the HTTP request, applying the timeout, logging delivery failures, and integrating with sidecar lifecycle/actions. Current PHP MVP path: ```mermaid flowchart LR Eval["PHP native evaluation<br/>ddog_ffe_evaluate"] Batch["PHP tracer native memory<br/>request/thread-local exposure batch"] Shutdown["PHP RSHUTDOWN<br/>flush exposure batch"] Action["sidecar action<br/>record FFE exposures"] Domain["datadog-ffe<br/>feature: exposure-events<br/>types + cache + JSON encoder"] Sidecar["shared sidecar<br/>cross-request and cross-thread exposure cache"] Agent["Datadog Agent<br/>EVP proxy"] Intake["FFE exposure intake"] Eval -->|"doLog=true assignment"| Batch Batch --> Shutdown Shutdown --> Action Action --> Domain Domain --> Sidecar Sidecar --> Agent Agent --> Intake ``` Future Python/Ruby connection: ```mermaid flowchart LR PyToday["dd-trace-py today<br/>host-language exposure writer"] RbToday["dd-trace-rb today<br/>host-language exposure writer"] PyFuture["dd-trace-py future<br/>explicit native opt-in"] RbFuture["dd-trace-rb future<br/>explicit native opt-in"] Native["libdatadog caller-driven<br/>FFE exposure action"] Shared["shared sidecar<br/>dedupe + EVP delivery"] Agent["Datadog Agent<br/>EVP proxy"] PyToday -. "current direct EVP path" .-> Agent RbToday -. "current direct EVP path" .-> Agent PyFuture -. "after ownership switch" .-> Native RbFuture -. "after ownership switch" .-> Native Native --> Shared Shared --> Agent ``` The future Python/Ruby arrows are intentionally not active behavior in this PR. They show why the reusable code lives in `datadog-ffe` rather than directly in sidecar internals, while preserving today's host-language ownership. Why Python/Ruby do not double count today: - Python and Ruby use libdatadog for evaluation only; the evaluator returns assignment metadata and does not enqueue exposure telemetry as a side effect. - This PR adds a separate caller-driven sidecar action. Exposure emission happens only when an SDK explicitly records exposure candidates into that action. PHP wires this in its companion PR; Python and Ruby do not. - Python and Ruby therefore keep exactly their current host-language EVP exposure writers. They are not also sending exposure candidates through this native sidecar path. - The sidecar cache only deduplicates exposure candidates that enter the native sidecar path. It cannot protect direct host-language EVP writers, so future Python/Ruby migration must switch ownership to native logging and disable/bypass the host exposure writer for the same evaluations. Reference implementation check: dd-trace-java follows the same exposure semantics and user ergonomics. Java's `DDEvaluator` is SDK-owned evaluation code; after resolving an assignment, it checks allocation `doLog`, builds an exposure event with flag, variant, allocation, targeting key, and context, and dispatches it through `FeatureFlaggingGateway`. `ExposureWriterImpl` subscribes to those exposure events, queues them, deduplicates with an LRU exposure cache, serializes service/env/version context, and posts to the Agent EVP proxy. Application code only calls the OpenFeature provider; it does not call an exposure API. PHP mirrors that canonical shape, with PHP-specific lifecycle mechanics: the dd-trace-php evaluation bridge records `doLog=true` exposure candidates internally, request shutdown flushes the batch, and this PR's sidecar path owns cross-request deduplication and EVP delivery. For future Python/Ruby migration, the same rule applies: wire native exposure recording inside the SDK-owned evaluation path, and turn off the existing host-language exposure writer for those evaluations. ## Decisions No telemetry is emitted automatically from shared libdatadog evaluator calls. SDKs must explicitly enqueue FFE telemetry actions. This remains required for Python/Ruby coexistence because those SDKs currently log exposures and metrics in host-language code. The sidecar cache deduplicates only exposure candidates sent through this native sidecar path; it cannot deduplicate direct host-language EVP writers. Future Python/Ruby migration must be an ownership switch, not an additional writer. When those SDKs opt into this native exposure path, their host-language exposure writers must be disabled or bypassed for the same evaluations to avoid double counting. ## Validation Current head (`8be471fbc`) local validation: ```sh cd /Users/leo.romanovsky/go/src/github.com/DataDog/libdatadog-ffe-sidecar-exposures cargo fmt --check cargo test -p datadog-ffe --features exposure-events telemetry::exposures cargo test -p datadog-sidecar ffe_exposure cargo check -p datadog-ffe cargo check -p datadog-sidecar-ffi ``` Results: datadog-ffe exposure tests passed (4 passed), sidecar exposure tests passed (6 passed), default datadog-ffe check passed, sidecar FFI check passed, fmt check passed with only the repo stable-rustfmt warnings. Prior downstream PHP behavior validation before the reusable-crate refactor, from DataDog/dd-trace-php#3910 using this PR at `6d23848a`: ```text ffe-dogfooding subject=php-3910-split-1779981442 php7_exposures=1 php8_exposures=1 php7_metrics=0 php8_metrics=0 ``` System-tests downstream validation: ```sh TEST_LIBRARY=php ./run.sh FEATURE_FLAGGING_AND_EXPERIMENTATION tests/ffe/test_exposures.py -vv ``` Result: 11 passed in 77.53 seconds. Related PRs: DataDog/dd-trace-php#3906, DataDog/dd-trace-php#3910, #2052, DataDog/system-tests#7031. Co-authored-by: leo.romanovsky <leo.romanovsky@datadoghq.com>
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Motivation
PHP FFE exposure logging now lives in the native dd-trace-php/runtime path and needs the shared FFE exposure system tests enabled so regressions are caught outside local dogfooding.
Planning/reference doc: https://docs.google.com/document/d/1NvMfTpZWLBlFmEFNjdnlMyeVpy5l7KD8qujGFco6w2w/edit?tab=t.0
Changes
This PR enables
tests/ffe/test_exposures.pyfor PHP atv1.21.0-dev.#7003 has already merged to
main, so this PR is now intentionally just one manifest activation on top ofmain. It does not enable FFE evaluation-metric tests; those belong to the separate metrics validation stack for DataDog/dd-trace-php#3911 and #7033.Decisions
The scope is deliberately one manifest activation. The shared exposure tests already cover the required product behavior: event generation, multiple RC files, malformed/empty RC handling, same-subject deduplication, different-subject emission, allocation/variant changes,
doLog=false, missing flags, and empty targeting keys.The PHP behavior being validated here is implemented in DataDog/dd-trace-php#3910 and the sidecar delivery/cache support is implemented in DataDog/libdatadog#2026.
Related PRs
Validation
Current branch state after rebase onto
main:Current PR diff is one file, enabling only
tests/ffe/test_exposures.pyfor PHP atv1.21.0-dev.Earlier local behavior validation for this activation used a matched PHP 8.2 NTS artifact and the
php-fpm-8.2weblog:Result:
11 passed in 78.22s.