fix: ServiceName default should include executable name

opentelemetry-sdk/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## vNext
 
+- Fix `service.name` Resource attribute fallback to follow OpenTelemetry
+  specification by using `unknown_service:<process.executable.name>` format when
+  service name is not explicitly configured. Previously, it only used
+  `unknown_service`.
 - Fix `SpanExporter::shutdown()` default timeout from 5 nanoseconds to 5 seconds.
 - **Breaking** `SpanExporter` trait methods `shutdown`, `shutdown_with_timeout`, and `force_flush` now take `&self` instead of `&mut self` for consistency with `LogExporter` and `PushMetricExporter`. Implementers using interior mutability (e.g., `Mutex`, `AtomicBool`) require no changes.
 - Added `Resource::get_ref(&self, key: &Key) -> Option<&Value>` to allow retrieving a reference to a resource value without cloning.

opentelemetry-sdk/src/logs/logger_provider.rs

@@ -477,11 +477,15 @@ mod tests {
             let _ = super::SdkLoggerProvider::builder()
                 .with_log_processor(processor_with_resource.clone())
                 .build();
-            assert_resource(
-                &processor_with_resource,
-                &exporter_with_resource,
-                SERVICE_NAME,
-                Some("unknown_service"),
+            let service_name = processor_with_resource
+                .resource()
+                .get(&Key::from_static_str(SERVICE_NAME))
+                .map(|v| v.to_string())
+                .unwrap();
+            assert!(
+                service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                service_name
             );
             assert_telemetry_resource(&processor_with_resource, &exporter_with_resource);
         });
@@ -516,11 +520,15 @@ mod tests {
                 let _ = super::SdkLoggerProvider::builder()
                     .with_log_processor(processor_with_resource.clone())
                     .build();
-                assert_resource(
-                    &processor_with_resource,
-                    &exporter_with_resource,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = processor_with_resource
+                    .resource()
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(
                     &processor_with_resource,
@@ -558,11 +566,15 @@ mod tests {
                     )
                     .with_log_processor(processor_with_resource.clone())
                     .build();
-                assert_resource(
-                    &processor_with_resource,
-                    &exporter_with_resource,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = processor_with_resource
+                    .resource()
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(
                     &processor_with_resource,

opentelemetry-sdk/src/metrics/meter_provider.rs

@@ -461,10 +461,15 @@ mod tests {
             let default_meter_provider = super::SdkMeterProvider::builder()
                 .with_reader(reader)
                 .build();
-            assert_resource(
-                &default_meter_provider,
-                SERVICE_NAME,
-                Some("unknown_service"),
+            let service_name = default_meter_provider.inner.pipes.0[0]
+                .resource
+                .get(&Key::from_static_str(SERVICE_NAME))
+                .map(|v| v.to_string())
+                .unwrap();
+            assert!(
+                service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                service_name
             );
             assert_telemetry_resource(&default_meter_provider);
         });
@@ -491,10 +496,15 @@ mod tests {
                 let env_resource_provider = super::SdkMeterProvider::builder()
                     .with_reader(reader3)
                     .build();
-                assert_resource(
-                    &env_resource_provider,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = env_resource_provider.inner.pipes.0[0]
+                    .resource
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(&env_resource_provider, "key1", Some("value1"));
                 assert_resource(&env_resource_provider, "k3", Some("value2"));
@@ -520,10 +530,15 @@ mod tests {
                             .build(),
                     )
                     .build();
-                assert_resource(
-                    &user_provided_resource_config_provider,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = user_provided_resource_config_provider.inner.pipes.0[0]
+                    .resource
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(
                     &user_provided_resource_config_provider,

opentelemetry-sdk/src/resource/env.rs

@@ -86,7 +86,19 @@ impl ResourceDetector for SdkProvidedResourceDetector {
                             .detect()
                             .get(&Key::new(super::SERVICE_NAME))
                     })
-                    .unwrap_or_else(|| "unknown_service".into()),
+                    .unwrap_or_else(|| {
+                        // Fallback to unknown_service:<process.executable.name> per spec
+                        // https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/resource/sdk.md#sdk-provided-resource-attributes
+                        env::current_exe()
+                            .ok()
+                            .and_then(|path| {
+                                path.file_name()
+                                    .and_then(|name| name.to_str())
+                                    .map(|name| format!("unknown_service:{}", name))
+                            })
+                            .unwrap_or_else(|| "unknown_service".to_string())
+                            .into()
+                    }),
             )])
             .build()
     }
@@ -135,11 +147,18 @@ mod tests {
 
     #[test]
     fn test_sdk_provided_resource_detector() {
-        // Ensure no env var set
+        // Ensure no env var set - should fallback to unknown_service:<executable_name>
+        // For cargo tests, the executable name is typically <crate_name>-<hash>
         let no_env = SdkProvidedResourceDetector.detect();
-        assert_eq!(
-            no_env.get(&Key::from_static_str(crate::resource::SERVICE_NAME)),
-            Some(Value::from("unknown_service")),
+        let service_name = no_env
+            .get(&Key::from_static_str(crate::resource::SERVICE_NAME))
+            .map(|v| v.to_string())
+            .unwrap();
+
+        assert!(
+            service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+            "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+            service_name
         );
 
         temp_env::with_var(OTEL_SERVICE_NAME, Some("test service"), || {

opentelemetry-sdk/src/trace/provider.rs

@@ -606,10 +606,16 @@ mod tests {
         // If users didn't provide a resource and there isn't a env var set. Use default one.
         temp_env::with_var_unset("OTEL_RESOURCE_ATTRIBUTES", || {
             let default_config_provider = super::SdkTracerProvider::builder().build();
-            assert_resource(
-                &default_config_provider,
-                SERVICE_NAME,
-                Some("unknown_service"),
+            let service_name = default_config_provider
+                .config()
+                .resource
+                .get(&Key::from_static_str(SERVICE_NAME))
+                .map(|v| v.to_string())
+                .unwrap();
+            assert!(
+                service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                service_name
             );
             assert_telemetry_resource(&default_config_provider);
         });
@@ -631,10 +637,16 @@ mod tests {
             Some("key1=value1, k2, k3=value2"),
             || {
                 let env_resource_provider = super::SdkTracerProvider::builder().build();
-                assert_resource(
-                    &env_resource_provider,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = env_resource_provider
+                    .config()
+                    .resource
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(&env_resource_provider, "key1", Some("value1"));
                 assert_resource(&env_resource_provider, "k3", Some("value2"));
@@ -658,10 +670,16 @@ mod tests {
                             .build(),
                     )
                     .build();
-                assert_resource(
-                    &user_provided_resource_config_provider,
-                    SERVICE_NAME,
-                    Some("unknown_service"),
+                let service_name = user_provided_resource_config_provider
+                    .config()
+                    .resource
+                    .get(&Key::from_static_str(SERVICE_NAME))
+                    .map(|v| v.to_string())
+                    .unwrap();
+                assert!(
+                    service_name.starts_with("unknown_service:opentelemetry_sdk-"),
+                    "Expected service name to start with 'unknown_service:opentelemetry_sdk-', got: {}",
+                    service_name
                 );
                 assert_resource(
                     &user_provided_resource_config_provider,