Optimize Resource Sharing Across Exporters with Arc Implementation

opentelemetry-sdk/CHANGELOG.md

@@ -8,6 +8,9 @@
 - [#1471](https://github.com/open-telemetry/opentelemetry-rust/pull/1471) Configure batch log record processor via [`OTEL_BLRP_*`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk-environment-variables.md#batch-logrecord-processor) environment variables and via `OtlpLogPipeline::with_batch_config`
 - [#1503](https://github.com/open-telemetry/opentelemetry-rust/pull/1503) Make the documentation for In-Memory exporters visible.
 
+- [#1526](https://github.com/open-telemetry/opentelemetry-rust/pull/1526) 
+Performance Improvement : Creating Spans and LogRecords are now faster, by avoiding expensive cloning of `Resource` for every Span/LogRecord.
+
 ### Changed
 
 - **Breaking**

opentelemetry-sdk/src/resource/mod.rs

@@ -34,13 +34,22 @@
 use std::borrow::Cow;
 use std::collections::{hash_map, HashMap};
 use std::ops::Deref;
+use std::sync::Arc;
 use std::time::Duration;
 
+/// Inner structure of `Resource` holding the actual data.
+/// This structure is designed to be shared among `Resource` instances via `Arc`.
+#[derive(Debug, Clone, PartialEq)]
+struct ResourceInner {
+    attrs: HashMap<Key, Value>,
+    schema_url: Option<Cow<'static, str>>,
+}
+
 /// An immutable representation of the entity producing telemetry as attributes.
+/// Utilizes `Arc` for efficient sharing and cloning.
 #[derive(Clone, Debug, PartialEq)]
 pub struct Resource {
-    attrs: HashMap<Key, Value>,
-    schema_url: Option<Cow<'static, str>>,
+    inner: Arc<ResourceInner>,
 }
 
 impl Default for Resource {
@@ -58,10 +67,13 @@
 
 impl Resource {
     /// Creates an empty resource.
+    /// This is the basic constructor that initializes a resource with no attributes and no schema URL.
     pub fn empty() -> Self {
-        Self {
-            attrs: Default::default(),
-            schema_url: None,
+        Resource {
+            inner: Arc::new(ResourceInner {
+                attrs: HashMap::new(),
+                schema_url: None,
+            }),
         }
     }
 
@@ -70,13 +82,17 @@
     /// Values are de-duplicated by key, and the first key-value pair with a non-empty string value
     /// will be retained
     pub fn new<T: IntoIterator<Item = KeyValue>>(kvs: T) -> Self {
-        let mut resource = Resource::empty();
-
-        for kv in kvs.into_iter() {
-            resource.attrs.insert(kv.key, kv.value);
+        let mut attrs = HashMap::new();
+        for kv in kvs {
+            attrs.insert(kv.key, kv.value);
         }
 
-        resource
+        Resource {
+            inner: Arc::new(ResourceInner {
+                attrs,
+                schema_url: None,
+            }),
+        }
     }
 
     /// Create a new `Resource` from a key value pairs and [schema url].
@@ -92,9 +108,22 @@
         KV: IntoIterator<Item = KeyValue>,
         S: Into<Cow<'static, str>>,
     {
-        let mut resource = Self::new(kvs);
-        resource.schema_url = Some(schema_url.into());
-        resource
+        let schema_url_str = schema_url.into();
+        let normalized_schema_url = if schema_url_str.is_empty() {
+            None
+        } else {
+            Some(schema_url_str)
+        };
+        let mut attrs = HashMap::new();
+        for kv in kvs {
+            attrs.insert(kv.key, kv.value);
+        }
+        Resource {
+            inner: Arc::new(ResourceInner {
+                attrs,
+                schema_url: normalized_schema_url,
+            }),
+        }
     }
 
     /// Create a new `Resource` from resource detectors.
@@ -104,9 +133,12 @@
         let mut resource = Resource::empty();
         for detector in detectors {
             let detected_res = detector.detect(timeout);
+            // This call ensures that if the Arc is not uniquely owned,
+            // the data is cloned before modification, preserving safety.
+            // If the Arc is uniquely owned, it simply returns a mutable reference to the data.
+            let inner = Arc::make_mut(&mut resource.inner);
             for (key, value) in detected_res.into_iter() {
-                // using insert instead of merge to avoid clone.
-                resource.attrs.insert(key, value);
+                inner.attrs.insert(Key::new(key.clone()), value.clone());
             }
         }
 
@@ -129,87 +161,62 @@
     ///
     /// [Schema url]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/schemas/overview.md#schema-url
     pub fn merge<T: Deref<Target = Self>>(&self, other: T) -> Self {
-        if self.attrs.is_empty() {
+        if self.is_empty() {
             return other.clone();
         }
-        if other.attrs.is_empty() {
+        if other.is_empty() {
             return self.clone();
         }
-
-        let mut resource = Resource::empty();
-
-        // attrs from self take the less priority, even when the new value is empty.
-        for (k, v) in self.attrs.iter() {
-            resource.attrs.insert(k.clone(), v.clone());
-        }
-        for (k, v) in other.attrs.iter() {
-            resource.attrs.insert(k.clone(), v.clone());
+        let mut combined_attrs = self.inner.attrs.clone();
+        for (k, v) in other.inner.attrs.iter() {
+            combined_attrs.insert(k.clone(), v.clone());
         }
-
-        if self.schema_url == other.schema_url {
-            resource.schema_url = self.schema_url.clone();
-        } else if self.schema_url.is_none() {
-            // if the other resource has schema url, use it.
-            if other.schema_url.is_some() {
-                resource.schema_url = other.schema_url.clone();
-            }
-            // else empty schema url.
-        } else {
-            // if self has schema url, use it.
-            if other.schema_url.is_none() {
-                resource.schema_url = self.schema_url.clone();
-            }
+        // Resolve the schema URL according to the precedence rules
+        let combined_schema_url = match (&self.inner.schema_url, &other.inner.schema_url) {
+            // If both resources have a schema URL and it's the same, use it
+            (Some(url1), Some(url2)) if url1 == url2 => Some(url1.clone()),
+            // If both resources have a schema URL but they are not the same, the schema URL will be empty
+            (Some(_), Some(_)) => None,
+            // If this resource does not have a schema URL, and the other resource has a schema URL, it will be used
+            (None, Some(url)) => Some(url.clone()),
+            // If this resource has a schema URL, it will be used (covers case 1 and any other cases where `self` has a schema URL)
+            (Some(url), _) => Some(url.clone()),
+            // If both resources do not have a schema URL, the schema URL will be empty
+            (None, None) => None,
+        };
+        Resource {
+            inner: Arc::new(ResourceInner {
+                attrs: combined_attrs,
+                schema_url: combined_schema_url,
+            }),
         }
-
-        resource
     }
 
     /// Return the [schema url] of the resource. If the resource does not have a schema url, return `None`.
     ///
     /// [schema url]: https://github.com/open-telemetry/opentelemetry-specification/blob/v1.9.0/specification/schemas/overview.md#schema-url
     pub fn schema_url(&self) -> Option<&str> {
-        self.schema_url.as_ref().map(|s| s.as_ref())
+        self.inner.schema_url.as_ref().map(|s| s.as_ref())
     }
 
     /// Returns the number of attributes for this resource
     pub fn len(&self) -> usize {
-        self.attrs.len()
+        self.inner.attrs.len()
     }
 
     /// Returns `true` if the resource contains no attributes.
     pub fn is_empty(&self) -> bool {
-        self.attrs.is_empty()
+        self.inner.attrs.is_empty()
     }
 
     /// Gets an iterator over the attributes of this resource, sorted by key.
     pub fn iter(&self) -> Iter<'_> {
-        self.into_iter()
+        Iter(self.inner.attrs.iter())
     }
 
     /// Retrieve the value from resource associate with given key.
     pub fn get(&self, key: Key) -> Option<Value> {
-        self.attrs.get(&key).cloned()
-    }
-}
-
-/// An owned iterator over the entries of a `Resource`.
-#[derive(Debug)]
-pub struct IntoIter(hash_map::IntoIter<Key, Value>);
-
-impl Iterator for IntoIter {
-    type Item = (Key, Value);
-
-    fn next(&mut self) -> Option<Self::Item> {
-        self.0.next()
-    }
-}
-
-impl IntoIterator for Resource {
-    type Item = (Key, Value);
-    type IntoIter = IntoIter;
-
-    fn into_iter(self) -> Self::IntoIter {
-        IntoIter(self.attrs.into_iter())
+        self.inner.attrs.get(&key).cloned()
     }
 }
 
@@ -230,7 +237,7 @@
     type IntoIter = Iter<'a>;
 
     fn into_iter(self) -> Self::IntoIter {
-        Iter(self.attrs.iter())
+        Iter(self.inner.attrs.iter())
     }
 }
 
@@ -264,13 +271,10 @@
         let mut expected_attrs = HashMap::new();
         expected_attrs.insert(Key::new("a"), Value::from("final"));
 
-        assert_eq!(
-            Resource::new(args_with_dupe_keys),
-            Resource {
-                attrs: expected_attrs,
-                schema_url: None,
-            }
-        );
+        let resource = Resource::new(args_with_dupe_keys);
+        let resource_inner = Arc::try_unwrap(resource.inner).expect("Failed to unwrap Arc");
+        assert_eq!(resource_inner.attrs, expected_attrs);
+        assert_eq!(resource_inner.schema_url, None);
     }
 
     #[test]
@@ -293,13 +297,14 @@
         expected_attrs.insert(Key::new("c"), Value::from("c-value"));
         expected_attrs.insert(Key::new("d"), Value::from(""));
 
-        assert_eq!(
-            resource_a.merge(&resource_b),
-            Resource {
+        let expected_resource = Resource {
+            inner: Arc::new(ResourceInner {
                 attrs: expected_attrs,
-                schema_url: None,
-            }
-        );
+                schema_url: None, // Assuming schema_url handling if needed
+            }),
+        };
+
+        assert_eq!(resource_a.merge(&resource_b), expected_resource);
     }
 
     #[test]
@@ -317,24 +322,32 @@
             (None, None, None),
         ];
 
-        for (schema_url, other_schema_url, expect_schema_url) in test_cases.into_iter() {
-            let mut resource = Resource::new(vec![KeyValue::new("key", "")]);
-            resource.schema_url = schema_url.map(Into::into);
+        for (schema_url_a, schema_url_b, expected_schema_url) in test_cases.into_iter() {
+            let resource_a = Resource::from_schema_url(
+                vec![KeyValue::new("key", "")],
+                schema_url_a.unwrap_or(""),
+            );
+            let resource_b = Resource::from_schema_url(
+                vec![KeyValue::new("key", "")],
+                schema_url_b.unwrap_or(""),
+            );
 
-            let mut other_resource = Resource::new(vec![KeyValue::new("key", "")]);
-            other_resource.schema_url = other_schema_url.map(Into::into);
+            let merged_resource = resource_a.merge(&resource_b);
+            let result_schema_url = merged_resource.schema_url();
 
             assert_eq!(
-                resource.merge(&other_resource).schema_url,
-                expect_schema_url.map(Into::into)
+                result_schema_url.map(|s| s as &str),
+                expected_schema_url,
+                "Merging schema_url_a {:?} with schema_url_b {:?} did not yield expected result {:?}",
+                schema_url_a, schema_url_b, expected_schema_url
             );
         }
 
         // if only one resource contains key value pairs
         let resource = Resource::from_schema_url(vec![], "http://schema/a");
         let other_resource = Resource::new(vec![KeyValue::new("key", "")]);
 
-        assert_eq!(resource.merge(&other_resource).schema_url, None);
+        assert_eq!(resource.merge(&other_resource).schema_url(), None);
     }
 
     #[test]