Calls to MeterProviderBuilder::with_resource are now additive

Author: martintmk

opentelemetry-sdk/CHANGELOG.md

@@ -2,7 +2,8 @@
 
 ## vNext
 
-- *Breaking* Make `force_flush()` in `PushMetricExporter` synchronous
+- *Breaking*: Calls to `MeterProviderBuilder::with_resource` are now additive ([#2324](https://github.com/open-telemetry/opentelemetry-rust/issues/2324)).
+- *Breaking*: Make `force_flush()` in `PushMetricExporter` synchronous
 
 ## 0.28.0
 

opentelemetry-sdk/src/metrics/meter_provider.rs

@@ -232,10 +232,16 @@ impl MeterProviderBuilder {
     /// with all [Meter]s the [MeterProvider] will create.
     ///
     /// By default, if this option is not used, the default [Resource] will be used.
+    /// Note that the calls to this method are additive, each call merges the provided
+    /// resource with the previous one.
     ///
     /// [Meter]: opentelemetry::metrics::Meter
     pub fn with_resource(mut self, resource: Resource) -> Self {
-        self.resource = Some(resource);
+        self.resource = match self.resource {
+            Some(existing) => Some(existing.merge(&resource)),
+            None => Some(resource),
+        };
+
         self
     }
 
@@ -331,6 +337,7 @@ mod tests {
     use opentelemetry::{global, InstrumentationScope};
     use opentelemetry::{Key, KeyValue, Value};
     use std::env;
+    use crate::metrics::SdkMeterProvider;
 
     #[test]
     fn test_meter_provider_resource() {
@@ -553,4 +560,20 @@ mod tests {
 
         assert_eq!(provider.inner.meters.lock().unwrap().len(), 5);
     }
+
+    #[test]
+    fn with_resource_multiple_calls_ensure_additive() {
+        let builder = SdkMeterProvider::builder()
+            .with_resource(Resource::new(vec![KeyValue::new("key1", "value1")]))
+            .with_resource(Resource::new(vec![KeyValue::new("key2", "value2")]))
+            .with_resource(Resource::builder_empty().with_schema_url(vec![], "http://example.com").build())
+            .with_resource(Resource::new(vec![KeyValue::new("key3", "value3")]));
+
+        let resource = builder.resource.unwrap();
+
+        assert_eq!(resource.get(&Key::from_static_str("key1")), Some(Value::from("value1")));
+        assert_eq!(resource.get(&Key::from_static_str("key2")), Some(Value::from("value2")));
+        assert_eq!(resource.get(&Key::from_static_str("key3")), Some(Value::from("value3")));
+        assert_eq!(resource.schema_url(), Some("http://example.com"));
+    }
 }

opentelemetry-sdk/src/resource/mod.rs

@@ -169,11 +169,11 @@ impl Resource {
     /// 5. If both resources do not have a schema url, the schema url will be empty.
     ///
     /// [Schema url]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/schemas/overview.md#schema-url
-    fn merge<T: Deref<Target = Self>>(&self, other: T) -> Self {
-        if self.is_empty() {
+    pub(crate) fn merge<T: Deref<Target = Self>>(&self, other: T) -> Self {
+        if self.is_empty() && self.schema_url().is_none() {
             return other.clone();
         }
-        if other.is_empty() {
+        if other.is_empty() && other.schema_url().is_none() {
             return self.clone();
         }
         let mut combined_attrs = self.inner.attrs.clone();
@@ -544,4 +544,15 @@ mod tests {
             },
         )
     }
+
+    #[test]
+    fn with_schema_url_for_empty_attributes() {
+        let resource = Resource::builder_empty()
+            .with_schema_url(vec![], "http://schema/a")
+            .build();
+        assert_eq!(resource.schema_url(), Some("http://schema/a"));
+
+        let resource = Resource::builder_empty().build().merge(&resource);
+        assert_eq!(resource.schema_url(), Some("http://schema/a"));
+    }
 }