Fix aggregation bug due to stale hash value (#1422)

Author: cijothomas

opentelemetry-sdk/CHANGELOG.md

@@ -5,6 +5,8 @@
 - Fix SimpleSpanProcessor to be consistent with log counterpart. Also removed
   dependency on crossbeam-channel.
   [1612](https://github.com/open-telemetry/opentelemetry-rust/pull/1612/files)
+- [#1422](https://github.com/open-telemetry/opentelemetry-rust/pull/1422)
+  Fix metrics aggregation bug when using Views to drop attributes.  
 
 ## v0.22.1
 

opentelemetry-sdk/src/attributes/set.rs

@@ -138,16 +138,20 @@ impl From<&Resource> for AttributeSet {
     }
 }
 
+fn calculate_hash(values: &[HashKeyValue]) -> u64 {
+    let mut hasher = DefaultHasher::new();
+    values.iter().fold(&mut hasher, |mut hasher, item| {
+        item.hash(&mut hasher);
+        hasher
+    });
+    hasher.finish()
+}
+
 impl AttributeSet {
     fn new(mut values: Vec<HashKeyValue>) -> Self {
         values.sort_unstable();
-        let mut hasher = DefaultHasher::new();
-        values.iter().fold(&mut hasher, |mut hasher, item| {
-            item.hash(&mut hasher);
-            hasher
-        });
-
-        AttributeSet(values, hasher.finish())
+        let hash = calculate_hash(&values);
+        AttributeSet(values, hash)
     }
 
     /// Returns the number of elements in the set.
@@ -165,7 +169,10 @@ impl AttributeSet {
     where
         F: Fn(&KeyValue) -> bool,
     {
-        self.0.retain(|kv| f(&kv.0))
+        self.0.retain(|kv| f(&kv.0));
+
+        // Recalculate the hash as elements are changed.
+        self.1 = calculate_hash(&self.0);
     }
 
     /// Iterate over key value pairs in the set

opentelemetry-sdk/src/metrics/mod.rs

@@ -532,7 +532,6 @@ mod tests {
     // "multi_thread" tokio flavor must be used else flush won't
     // be able to make progress!
     #[tokio::test(flavor = "multi_thread", worker_threads = 1)]
-    #[ignore = "Spatial aggregation is not yet implemented."]
     async fn spatial_aggregation_when_view_drops_attributes_counter() {
         // cargo test spatial_aggregation_when_view_drops_attributes_counter --features=metrics,testing