registry: add clear method

metrics-util/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - New layer -- `Router` -- for routing specific metrics to target downstream recorders.
+- `Registry::clear` allows clearing all metrics from the registry.
 
 ### Changed
 - Updated all deprecated usages of `crossbeam_epoch::Atomic<T>::compare_and_set` to `compare_exchange`.

metrics-util/src/registry.rs

@@ -123,6 +123,18 @@ where
         (hash, shard)
     }
 
+    /// Removes all metrics from the registry.
+    ///
+    /// This operation is eventually consistent: metrics will be removed piecemeal, and this method
+    /// does not ensure that callers will see the registry as entirely empty at any given point.
+    pub fn clear(&self) {
+        for shard in &self.shards {
+            for subshard in shard {
+                subshard.write().clear();
+            }
+        }
+    }
+
     /// Perform an operation on a given key.
     ///
     /// The `op` function will be called for the handle under the given `key`.