Fix parent based sampling in tracer

opentelemetry/src/api/trace/context.rs

@@ -42,6 +42,11 @@ pub trait TraceContextExt {
     /// ```
     fn span(&self) -> &dyn crate::trace::Span;
 
+    /// Used to see if a span has been marked as active
+    ///
+    /// This is useful for building tracers.
+    fn has_active_span(&self) -> bool;
+
     /// Returns a copy of this context with the span context included.
     ///
     /// This is useful for building propagators.
@@ -71,6 +76,10 @@ impl TraceContextExt for Context {
         }
     }
 
+    fn has_active_span(&self) -> bool {
+        self.get::<Span>().is_some()
+    }
+
     fn with_remote_span_context(&self, span_context: crate::trace::SpanContext) -> Self {
         self.with_value(RemoteSpanContext(span_context))
     }

opentelemetry/src/sdk/metrics/aggregators/array.rs

@@ -205,7 +205,7 @@ impl Quantile for PointsData {
             return Err(MetricsError::NoDataCollected);
         }
 
-        if q < 0.0 || q > 1.0 {
+        if !(0.0..=1.0).contains(&q) {
             return Err(MetricsError::InvalidQuantile);
         }
 

opentelemetry/src/sdk/metrics/aggregators/ddsketch.rs

@@ -116,7 +116,7 @@ impl Distribution for DDSKetchAggregator {}
 
 impl Quantile for DDSKetchAggregator {
     fn quantile(&self, q: f64) -> Result<Number> {
-        if q < 0.0 || q > 1.0 {
+        if !(0.0..=1.0).contains(&q) {
             return Err(MetricsError::InvalidQuantile);
         }
         self.inner.read().map_err(From::from).and_then(|inner| {

opentelemetry/src/sdk/trace/tracer.rs

@@ -172,9 +172,14 @@ impl crate::trace::Tracer for Tracer {
         let parent_span_context = builder
             .parent_context
             .as_ref()
-            .or_else(|| Some(cx.span().span_context()).filter(|cx| cx.is_valid()))
-            .or_else(|| cx.remote_span_context())
-            .filter(|cx| cx.is_valid());
+            .or_else(|| {
+                if cx.has_active_span() {
+                    Some(cx.span().span_context())
+                } else {
+                    None
+                }
+            })
+            .or_else(|| cx.remote_span_context());
         // Build context for sampling decision
         let (no_parent, trace_id, parent_span_id, remote_parent, parent_trace_flags) =
             parent_span_context
@@ -283,11 +288,12 @@ mod tests {
     use crate::{
         sdk::{
             self,
-            trace::{Config, SamplingDecision, SamplingResult, ShouldSample},
+            trace::{Config, Sampler, SamplingDecision, SamplingResult, ShouldSample},
         },
+        testing::trace::TestSpan,
         trace::{
-            Link, Span, SpanBuilder, SpanContext, SpanId, SpanKind, TraceId, TraceState, Tracer,
-            TracerProvider, TRACE_FLAG_SAMPLED,
+            Link, Span, SpanBuilder, SpanContext, SpanId, SpanKind, TraceContextExt, TraceId,
+            TraceState, Tracer, TracerProvider, TRACE_FLAG_SAMPLED,
         },
         Context, KeyValue,
     };
@@ -340,4 +346,19 @@ mod tests {
         let expected = span_context.trace_state();
         assert_eq!(expected.get("foo"), Some("notbar"))
     }
+
+    #[test]
+    fn drop_parent_based_children() {
+        let sampler = Sampler::ParentBased(Box::new(Sampler::AlwaysOn));
+        let config = Config::default().with_default_sampler(sampler);
+        let tracer_provider = sdk::trace::TracerProvider::builder()
+            .with_config(config)
+            .build();
+
+        let context = Context::current_with_span(TestSpan(SpanContext::empty_context()));
+        let tracer = tracer_provider.get_tracer("test", None);
+        let span = tracer.start_from_context("must_not_be_sampled", &context);
+
+        assert!(!span.span_context().is_sampled());
+    }
 }