Enable Ruby FFE APM span-enrichment parametric tests

[leoromanovsky]

Motivation

The FFE APM feature-flag span-enrichment contract (frozen against dd-trace-js#8343)
is now implemented in the Ruby tracer (DataDog/dd-trace-rb#5910). This PR enables the
existing frozen parametric suite tests/parametric/test_ffe/test_span_enrichment.py
for Ruby so the harness asserts Ruby's ffe_* tags (ffe_flags_enc,
ffe_subjects_enc, ffe_runtime_defaults) stay in parity with the backend/Trino
decode and the Node.js reference.

Changes

Two language-scoped changes, no cross-language drift:

1. utils/build/docker/ruby/parametric/server.rb — the /ffe/evaluate handler now
   re-activates the caller-supplied span's live TraceOperation around the
   evaluation (the in-process equivalent of the Node reference's
   tracer.scope().activate(span, fn) in utils/build/docker/nodejs/parametric/server.js).

   • OpenFeatureArgs now reads span_id (cast to Integer — the test client sends it as
     a string, DD_SPANS is keyed by integer span id).
   • The eval runs via call_context.activate!(trace_op) { ... } so the SDK's
     SpanEnrichmentHook — which keys its accumulator and its span_before_finish
     subscription by the active TraceOperation — aggregates every flag onto the
     test's real root span.
   • Missing/unknown span_id falls through to a plain eval; never raises.

2. manifests/ruby.yml — flip tests/parametric/test_ffe/test_span_enrichment.py
   from missing_feature to v2.36.0-dev.

Decisions

• Why call_context.activate! and not continue_from: — a continue_from: digest
  starts a new TraceOperation per call (Tracer#continue_trace! →
  start_trace(continue_from:)). Each /ffe/evaluate would then land on a throwaway
  forked root span, so multi-flag / multi-subject / child-span tests would aggregate
  nothing onto the test's actual root. Activating the stored live trace keeps all evals
  on the one trace the test created — matching the Node reference behavior exactly. This
  was a parametric-app harness fix; no dd-trace-rb source change was needed.

• Limit-test parity — serial IDs (200), subjects (10), experiments/subject (20),
  runtime defaults (5), 64-char value truncation all pass against the frozen assertions.

Validation results

Run locally against the dd-trace-rb#5910 gem (datadog-2.36.0.dev,
libdatadog-33.0.0.1.0):

TEST_LIBRARY=ruby ./run.sh PARAMETRIC -k span_enrichment
...
============================= 18 passed in 30.48s ==============================

All 18 cases green: delta-varint codec (5), serial-ID/subject aggregation, multiple
subjects tracked separately, child-span→root propagation, SHA256 subject hashing,
__dd_do_log gating, runtime-default detection + 64-char truncation, and all frozen
limits.

Host-arch note (not a code issue): utils/build/docker/ruby/parametric/Dockerfile
pins FROM --platform=linux/amd64. On an arm64 host the in-container native-ext build
of ext/libdatadog_api/di.c segfaults under QEMU x86_64 emulation
(make: *** [di.o] Segmentation fault). The 18-passing run above was produced on arm64
using a local-only workaround (dropping the --platform pin so the ext compiles
natively); that workaround is intentionally not part of this PR. The server.rb
delta validated is byte-identical to the one in this PR, and the gem/enrichment behavior
is platform-independent — so CI (amd64) exercises the same code path. Flagging the host
QEMU bug explicitly so the PR is not blocked on it.

[github-actions]

CODEOWNERS have been resolved as:

manifests/ruby.yml                                                      @DataDog/ruby-guild @DataDog/asm-ruby
utils/build/docker/ruby/parametric/server.rb                            @DataDog/ruby-guild @DataDog/asm-ruby @DataDog/system-tests-core

[datadog-prod-us1-6]

 

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⚠️ Warnings

🚦 3 Pipeline jobs failed

Testing the test | System Tests (ruby, dev) / parametric / parametric (2)     

🧪 12 Tests failed

tests.parametric.test_ffe.test_span_enrichment.Test_Span_Enrichment_Child_Span_Propagation.test_child_span_flag_evaluation_propagates_to_root[library_env0, parametric-ruby] from system_tests_suite  

AssertionError: ffe_flags_enc not found in root span meta: ['_dd.base_service', '_dd.svc_src', '_dd.p.dm', '_dd.p.ksr', 'language', 'runtime-id', '_dd.p.tid']
assert 'ffe_flags_enc' in {'_dd.base_service': 'server', '_dd.p.dm': '-0', '_dd.p.ksr': '1', '_dd.p.tid': '6a31df1500000000', ...}

self = <tests.parametric.test_ffe.test_span_enrichment.Test_Span_Enrichment_Child_Span_Propagation object at 0x7fbb8e596000>
test_agent = <utils.docker_fixtures._test_agent.TestAgentAPI object at 0x7fbb5e09c290>
test_library = <utils.docker_fixtures._test_clients._test_client_parametric.ParametricTestClientApi object at 0x7fbb5e5d6300>

    @parametrize("library_env", [{**DEFAULT_ENVVARS}])
    def test_child_span_flag_evaluation_propagates_to_root(
        self, test_agent: TestAgentAPI, test_library: APMLibrary
...

tests.parametric.test_ffe.test_span_enrichment.Test_Span_Enrichment_Default_Fallback.test_ffe_runtime_defaults_value_truncated_at_64_chars[library_env0, parametric-ruby] from system_tests_suite  

AssertionError: ffe_runtime_defaults not found in span meta: ['_dd.base_service', '_dd.svc_src', '_dd.p.dm', '_dd.p.ksr', 'language', 'runtime-id', '_dd.p.tid', '_dd.tags.process']
assert 'ffe_runtime_defaults' in {'_dd.base_service': 'server', '_dd.p.dm': '-0', '_dd.p.ksr': '1', '_dd.p.tid': '6a31df1d00000000', ...}

self = <tests.parametric.test_ffe.test_span_enrichment.Test_Span_Enrichment_Default_Fallback object at 0x7fcdcafd59a0>
test_agent = <utils.docker_fixtures._test_agent.TestAgentAPI object at 0x7fcdca0f6300>
test_library = <utils.docker_fixtures._test_clients._test_client_parametric.ParametricTestClientApi object at 0x7fcdca4f7890>

    @parametrize("library_env", [{**DEFAULT_ENVVARS}])
    def test_ffe_runtime_defaults_value_truncated_at_64_chars(
        self, test_agent: TestAgentAPI, test_library: APMLibrary
...

View all 12 test failures

Testing the test | System Tests (cpp_kong, dev) / Build end-to-end (kong)     

Testing the test | all-jobs-are-green     

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❄️ No new flaky tests detected

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