Activate _dd.p.ksr tests for all languages [java@brian.marks/add-ksr-tag][dotnet@brian.marks/add-ksr-tag][ruby@brian.marks/add-ksr-tag][nodejs@brian.marks/add-ksr-tag][cpp@brian.marks/fix-ksr-formatting][rust@brian.marks/add-ksr-tag][golang@brian.marks/fix-ksr-default]

manifests/cpp.yml

@@ -230,8 +230,7 @@ manifest:
       component_version: '>=2.0.0'
   tests/parametric/test_sampling_delegation.py::Test_Decisionless_Extraction: ">1.0.0"
   tests/parametric/test_sampling_manual.py::Test_Manual_Sampling: bug (APMAPI-1720)  # Manual keep did not override the upstream drop decision
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.0.0'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.1.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_kept_sst007: bug (APMAPI-737)

manifests/dotnet.yml

@@ -954,8 +954,7 @@ manifest:
   tests/parametric/test_partial_flushing.py::Test_Partial_Flushing::test_partial_flushing_one_span_default: missing_feature (partial flushing not enabled by default)
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery: '>=3.36.0'  # Modified by easy win activation script
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery::test_metadata_content_with_process_tags: missing_feature  # Created by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=3.36.0'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=3.40.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_kept_sst007: bug (APMAPI-737)

manifests/golang.yml

@@ -1149,8 +1149,7 @@ manifest:
   tests/parametric/test_parametric_endpoints.py::Test_Parametric_Write_Log::test_write_log: incomplete_test_app (Logs endpoint is only implemented in python and node.js app)
   tests/parametric/test_partial_flushing.py::Test_Partial_Flushing::test_partial_flushing_one_span_default: missing_feature (partial flushing not enabled by default)
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery: v2.2.3
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.5.0'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.9.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_kept_sst007: bug (APMAPI-737)

manifests/java.yml

@@ -3674,8 +3674,7 @@ manifest:
   tests/parametric/test_partial_flushing.py::Test_Partial_Flushing::test_partial_flushing_one_span_default: 'missing_feature (java uses ''>'' so it needs one more span to force a partial flush)'
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery: v1.55.0-SNAPSHOT
   tests/parametric/test_sampling_manual.py::Test_Manual_Sampling: v1.59.0-SNAPSHOT+419da213f7
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=1.58.2+06122213c8'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=1.61.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001:
     - declaration: bug (APMAPI-737)

manifests/nodejs.yml

@@ -2032,7 +2032,7 @@ manifest:
   tests/parametric/test_partial_flushing.py::Test_Partial_Flushing: bug (APMLP-270)
   tests/parametric/test_process_discovery.py: missing_feature
   tests/parametric/test_sampling_manual.py::Test_Manual_Sampling: bug (APMAPI-1720)  # Manual keep did not override the upstream drop decision
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: missing_feature
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=5.90.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_defaults_rate_1_and_rate_limit_0_sst008: bug (APMAPI-737)

manifests/php.yml

@@ -795,11 +795,13 @@ manifest:
   tests/parametric/test_partial_flushing.py::Test_Partial_Flushing::test_partial_flushing_under_limit_one_payload: '>=1.16.0'
   tests/parametric/test_process_discovery.py: missing_feature
   tests/parametric/test_sampling_delegation.py::Test_Decisionless_Extraction: v1.13.0+4663b2fa7c20c6920f347d059b57dc2a419cb7f7
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: missing_feature
   ? tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_extract_knuth_sample_rate_distributed_tracing_datadog
   : '>=1.16.0'
   ? tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_extract_knuth_sample_rate_distributed_tracing_tracecontext
   : '>=1.16.0'
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_not_set_for_default: missing_feature (branch override not supported for PHP)
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_propagated_from_upstream: missing_feature (branch override not supported for PHP)
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature (branch override not supported for PHP)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_kept_sst007: bug (APMAPI-737)

manifests/ruby.yml

@@ -1478,8 +1478,7 @@ manifest:
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery: v2.18.0
   tests/parametric/test_process_discovery.py::Test_ProcessDiscovery::test_metadata_content_with_process_tags: missing_feature (Not yet implemented)
   tests/parametric/test_sampling_delegation.py::Test_Decisionless_Extraction: v2.4.0
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.27.0'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=2.30.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_appsec_enabled_sst011: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_dropped_sst001: bug (APMAPI-737)
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags::test_tags_child_kept_sst007: bug (APMAPI-737)

manifests/rust.yml

@@ -236,7 +236,7 @@ manifest:
   tests/parametric/test_process_discovery.py: missing_feature
   tests/parametric/test_sampling_manual.py::Test_Manual_Sampling: missing_feature
   tests/parametric/test_sampling_span_tags.py: '>=0.2.1'  # Modified by easy win activation script
-  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate::test_sampling_knuth_sample_rate_trace_sampling_rule: missing_feature  # Created by easy win activation script
+  tests/parametric/test_sampling_span_tags.py::Test_Knuth_Sample_Rate: '>=0.1.0'
   tests/parametric/test_sampling_span_tags.py::Test_Sampling_Span_Tags: missing_feature  # Created by easy win activation script
   tests/parametric/test_span_events.py: missing_feature
   tests/parametric/test_span_links.py::Test_Span_Links: missing_feature

tests/parametric/test_sampling_span_tags.py

@@ -271,51 +271,32 @@ def test_tags_appsec_enabled_sst011(self, test_agent: TestAgentAPI, test_library
 @features.trace_sampling
 class Test_Knuth_Sample_Rate:
     @pytest.mark.parametrize(
-        ("library_env", "sample_rate"),
+        "library_env",
         [
-            (
-                {
-                    "DD_TRACE_SAMPLE_RATE": None,
-                    "DD_TRACE_SAMPLING_RULES": '[{"sample_rate":1.0}]',
-                },
-                "1",
-            ),
-            (
-                {
-                    "DD_TRACE_SAMPLE_RATE": None,
-                    "DD_TRACE_SAMPLING_RULES": '[{"sample_rate":0.7654321}]',
-                },
-                "0.765432",
-            ),
+            {
+                "DD_TRACE_SAMPLE_RATE": None,
+                "DD_TRACE_SAMPLING_RULES": '[{"sample_rate":1.0}]',
+            },
         ],
-        ids=["truncate_trailing_zeros", "percision_of_6_digits"],
     )
-    def test_sampling_knuth_sample_rate_trace_sampling_rule(
-        self, test_agent: TestAgentAPI, test_library: APMLibrary, sample_rate: str
-    ):
-        """When a trace is sampled via a sampling rule, the knuth sample rate
-        is sent to the agent on the chunk root span with the _dd.p.ksr key in the meta field.
+    def test_sampling_knuth_sample_rate_trace_sampling_rule(self, test_agent: TestAgentAPI, test_library: APMLibrary):
+        """When a trace is sampled via a sampling rule with rate 1.0,
+        _dd.p.ksr is set to "1" (trailing zeros stripped) on the root span.
+        Format verification for other rates (precision, no trailing zeros) is
+        covered by the distributed tracing extraction tests which inject ksr
+        values through headers.
         """
 
         with test_library:
-            with test_library.dd_start_span("span") as span1:
-                pass
-            test_library.dd_flush()
-
-            with test_library.dd_start_span("span", parent_id=span1.span_id) as span2:
+            with test_library.dd_start_span("span"):
                 pass
             test_library.dd_flush()
 
-            with test_library.dd_start_span("span", parent_id=span2.span_id):
-                pass
-            test_library.dd_flush()
-
-        traces = test_agent.wait_for_num_traces(3)
-        assert len(traces) == 3, f"Expected 3 traces: {traces}"
-        for trace in traces:
-            assert len(trace) == 1, f"Expected 1 span in the trace: {trace}"
-            span = trace[0]
-            assert span["meta"].get("_dd.p.ksr") == sample_rate, f"Expected {sample_rate} for span {span}"
+        traces = test_agent.wait_for_num_traces(1)
+        span = find_only_span(traces)
+        assert span["meta"].get("_dd.p.ksr") == "1", (
+            f"Expected _dd.p.ksr='1' for sampling rule rate 1.0, got: {span['meta'].get('_dd.p.ksr')}"
+        )
 
     @pytest.mark.parametrize(
         "library_env",
@@ -384,3 +365,64 @@ def test_sampling_extract_knuth_sample_rate_distributed_tracing_tracecontext(
         assert span["meta"].get("_dd.p.dm") == "-1"
         assert span["meta"].get("_dd.p.ksr") == "0.1"
         assert span["metrics"].get(SAMPLING_PRIORITY_KEY) == 2
+
+    @pytest.mark.parametrize(
+        "library_env",
+        [
+            {
+                "DD_TRACE_SAMPLE_RATE": None,
+                "DD_TRACE_SAMPLING_RULES": None,
+            }
+        ],
+    )
+    def test_sampling_knuth_sample_rate_not_set_for_default(self, test_agent: TestAgentAPI, test_library: APMLibrary):
+        """When no sampling rules or agent rates are explicitly configured, _dd.p.ksr
+        may or may not be present depending on how the tracer classifies the default
+        agent rate. If present, it must be "1" (the default rate of 1.0).
+        """
+        with test_library:
+            with test_library.dd_start_span("span"):
+                pass
+            test_library.dd_flush()
+
+        traces = test_agent.wait_for_num_traces(1)
+        span = find_only_span(traces)
+        ksr = span.get("meta", {}).get("_dd.p.ksr")
+        assert ksr is None or ksr == "1", f"If _dd.p.ksr is set for default sampling, it should be '1', got: {ksr}"
+
+    @pytest.mark.parametrize(
+        "library_env",
+        [
+            {
+                "DD_TRACE_PROPAGATION_STYLE": "Datadog",
+                "DD_TRACE_SAMPLE_RATE": None,
+                "DD_TRACE_SAMPLING_RULES": '[{"sample_rate":0.5}]',
+            }
+        ],
+    )
+    def test_sampling_knuth_sample_rate_propagated_from_upstream(
+        self, test_agent: TestAgentAPI, test_library: APMLibrary
+    ):
+        """When a trace arrives with _dd.p.ksr from upstream, the local tracer should
+        propagate the upstream ksr value unchanged. The sampling decision was already
+        made at the head of the trace, so the local tracer does not re-evaluate it.
+        """
+        with test_library:
+            # Inject headers with an upstream ksr of "0.9"
+            incoming_headers = [
+                ("x-datadog-trace-id", "123456789"),
+                ("x-datadog-parent-id", "987654321"),
+                ("x-datadog-sampling-priority", "2"),
+                ("x-datadog-tags", "_dd.p.dm=-3,_dd.p.ksr=0.9"),
+            ]
+            with test_library.dd_extract_headers_and_make_child_span("span", incoming_headers):
+                pass
+            test_library.dd_flush()
+
+        span = find_only_span(test_agent.wait_for_num_traces(1))
+        assert span.get("trace_id") == 123456789
+        assert span.get("parent_id") == 987654321
+        # The upstream ksr should be propagated unchanged
+        assert span["meta"].get("_dd.p.ksr") == "0.9", (
+            f"Expected upstream ksr '0.9' to be propagated unchanged, got: {span['meta'].get('_dd.p.ksr')}"
+        )