From 17855be169024c7ac961e3916958c844bb695198 Mon Sep 17 00:00:00 2001
From: Takahiro Ebato <takahiro.ebato@gmail.com>
Date: Tue, 31 Dec 2024 16:53:33 +0900
Subject: [PATCH] Retain empty tracer name as is instead of using default name
 (#2486)

Co-authored-by: Cijo Thomas <cijo.thomas@gmail.com>
---
 opentelemetry-sdk/CHANGELOG.md          |  4 +++
 opentelemetry-sdk/src/trace/mod.rs      | 44 ++++++++++++++++++++++++-
 opentelemetry-sdk/src/trace/provider.rs | 14 +++-----
 3 files changed, 51 insertions(+), 11 deletions(-)

diff --git a/opentelemetry-sdk/CHANGELOG.md b/opentelemetry-sdk/CHANGELOG.md
index 937e3b0c6b..b7a3f2a0da 100644
--- a/opentelemetry-sdk/CHANGELOG.md
+++ b/opentelemetry-sdk/CHANGELOG.md
@@ -211,6 +211,10 @@ metadata, a feature introduced in version 0.1.40. [#2418](https://github.com/ope
     - Continue enabling one of the async runtime feature flags: `rt-tokio`,
       `rt-tokio-current-thread`, or `rt-async-std`.
 
+- Bug fix: Empty Tracer names are retained as-is instead of replacing with
+  "rust.opentelemetry.io/sdk/tracer"
+  [#2486](https://github.com/open-telemetry/opentelemetry-rust/pull/2486)
+
 ## 0.27.1
 
 Released 2024-Nov-27
diff --git a/opentelemetry-sdk/src/trace/mod.rs b/opentelemetry-sdk/src/trace/mod.rs
index 4acf809022..e714364a85 100644
--- a/opentelemetry-sdk/src/trace/mod.rs
+++ b/opentelemetry-sdk/src/trace/mod.rs
@@ -48,7 +48,7 @@ mod tests {
 
     use super::*;
     use crate::{
-        testing::trace::InMemorySpanExporterBuilder,
+        testing::trace::{InMemorySpanExporter, InMemorySpanExporterBuilder},
         trace::span_limit::{DEFAULT_MAX_EVENT_PER_SPAN, DEFAULT_MAX_LINKS_PER_SPAN},
     };
     use opentelemetry::trace::{
@@ -342,4 +342,46 @@ mod tests {
             .attributes()
             .eq(&[KeyValue::new("test_k", "test_v")]));
     }
+
+    #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+    async fn empty_tracer_name_retained() {
+        async fn tracer_name_retained_helper(
+            tracer: super::Tracer,
+            provider: TracerProvider,
+            exporter: InMemorySpanExporter,
+        ) {
+            // Act
+            tracer.start("my_span").end();
+
+            // Force flush to ensure spans are exported
+            provider.force_flush().into_iter().for_each(|result| {
+                result.expect("failed to flush spans");
+            });
+
+            // Assert
+            let finished_spans = exporter
+                .get_finished_spans()
+                .expect("spans are expected to be exported.");
+            assert_eq!(finished_spans.len(), 1, "There should be a single span");
+
+            let tracer_name = finished_spans[0].instrumentation_scope.name();
+            assert_eq!(tracer_name, "", "The tracer name should be an empty string");
+
+            exporter.reset();
+        }
+
+        let exporter = InMemorySpanExporter::default();
+        let span_processor = SimpleSpanProcessor::new(Box::new(exporter.clone()));
+        let tracer_provider = TracerProvider::builder()
+            .with_span_processor(span_processor)
+            .build();
+
+        // Test Tracer creation in 2 ways, both with empty string as tracer name
+        let tracer1 = tracer_provider.tracer("");
+        tracer_name_retained_helper(tracer1, tracer_provider.clone(), exporter.clone()).await;
+
+        let tracer_scope = InstrumentationScope::builder("").build();
+        let tracer2 = tracer_provider.tracer_with_scope(tracer_scope);
+        tracer_name_retained_helper(tracer2, tracer_provider, exporter).await;
+    }
 }
diff --git a/opentelemetry-sdk/src/trace/provider.rs b/opentelemetry-sdk/src/trace/provider.rs
index 6d6f35fd94..447404cbb0 100644
--- a/opentelemetry-sdk/src/trace/provider.rs
+++ b/opentelemetry-sdk/src/trace/provider.rs
@@ -68,8 +68,8 @@ use crate::trace::{
 use crate::Resource;
 use crate::{export::trace::SpanExporter, trace::SpanProcessor};
 use opentelemetry::trace::TraceError;
-use opentelemetry::InstrumentationScope;
 use opentelemetry::{otel_debug, trace::TraceResult};
+use opentelemetry::{otel_info, InstrumentationScope};
 use std::borrow::Cow;
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, OnceLock};
@@ -252,20 +252,11 @@ impl TracerProvider {
     }
 }
 
-/// Default tracer name if empty string is provided.
-const DEFAULT_COMPONENT_NAME: &str = "rust.opentelemetry.io/sdk/tracer";
-
 impl opentelemetry::trace::TracerProvider for TracerProvider {
     /// This implementation of `TracerProvider` produces `Tracer` instances.
     type Tracer = Tracer;
 
     fn tracer(&self, name: impl Into<Cow<'static, str>>) -> Self::Tracer {
-        let mut name = name.into();
-
-        if name.is_empty() {
-            name = Cow::Borrowed(DEFAULT_COMPONENT_NAME)
-        };
-
         let scope = InstrumentationScope::builder(name).build();
         self.tracer_with_scope(scope)
     }
@@ -274,6 +265,9 @@ impl opentelemetry::trace::TracerProvider for TracerProvider {
         if self.inner.is_shutdown.load(Ordering::Relaxed) {
             return Tracer::new(scope, noop_tracer_provider().clone());
         }
+        if scope.name().is_empty() {
+            otel_info!(name: "TracerNameEmpty",  message = "Tracer name is empty; consider providing a meaningful name. Tracer will function normally and the provided name will be used as-is.");
+        };
         Tracer::new(scope, self.clone())
     }
 }