sdk: expose Tracer::id_generator() (#1934)

Author: djc

opentelemetry-sdk/src/trace/tracer.rs

@@ -11,7 +11,7 @@ use crate::{
     trace::{
         provider::TracerProvider,
         span::{Span, SpanData},
-        SpanLimits, SpanLinks,
+        IdGenerator, SpanEvents, SpanLimits, SpanLinks,
     },
     InstrumentationLibrary,
 };
@@ -22,8 +22,6 @@ use opentelemetry::{
 use std::fmt;
 use std::sync::Arc;
 
-use super::SpanEvents;
-
 /// `Tracer` implementation to create and manage spans
 #[derive(Clone)]
 pub struct Tracer {
@@ -160,6 +158,14 @@ impl Tracer {
             span_limits,
         )
     }
+
+    /// The [`IdGenerator`] associated with this tracer.
+    ///
+    // Note: this is necessary for tracing-opentelemetry's `PreSampledTracer`.
+    #[doc(hidden)]
+    pub fn id_generator(&self) -> &dyn IdGenerator {
+        &*self.provider.config().id_generator
+    }
 }
 
 impl opentelemetry::trace::Tracer for Tracer {