src/metrics/family.rs: Add remove and clear methods, and tests

CHANGELOG.md

@@ -8,12 +8,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 - Added support for the OpenMetrics protobuf format. See [PR 83].
+- Added a `remove` method to `Family` to allow the removal of a specified label
+  set from a family. See [PR 85].
+- Added a `clear` method to `Family` to allow the removal of all label sets
+  from a family. See [PR 85].
 
 ### Changed
 
 - Move`Encode` trait from `prometheus_client::encoding::text` to `prometheus_client::encoding`. See [PR 83].
 
 [PR 83]: https://github.com/prometheus/client_rust/pull/83
+[PR 85]: https://github.com/prometheus/client_rust/pull/85
 
 ## [0.18.0]
 

src/metrics/family.rs

@@ -234,6 +234,47 @@ impl<S: Clone + std::hash::Hash + Eq, M, C: MetricConstructor<M>> Family<S, M, C
         })
     }
 
+    /// Remove a label set from the metric family.
+    ///
+    /// Returns a bool indicating if a label set was removed or not.
+    ///
+    /// ```
+    /// # use prometheus_client::metrics::counter::{Atomic, Counter};
+    /// # use prometheus_client::metrics::family::Family;
+    /// #
+    /// let family = Family::<Vec<(String, String)>, Counter>::default();
+    ///
+    /// // Will create the metric with label `method="GET"` on first call and
+    /// // return a reference.
+    /// family.get_or_create(&vec![("method".to_owned(), "GET".to_owned())]).inc();
+    ///
+    /// // Will return `true`, indicating that the `method="GET"` label set was
+    /// // removed.
+    /// assert!(family.remove(&vec![("method".to_owned(), "GET".to_owned())]));
+    /// ```
+    pub fn remove(&self, label_set: &S) -> bool {
+        self.metrics.write().remove(label_set).is_some()
+    }
+
+    /// Clear all label sets from the metric family.
+    ///
+    /// ```
+    /// # use prometheus_client::metrics::counter::{Atomic, Counter};
+    /// # use prometheus_client::metrics::family::Family;
+    /// #
+    /// let family = Family::<Vec<(String, String)>, Counter>::default();
+    ///
+    /// // Will create the metric with label `method="GET"` on first call and
+    /// // return a reference.
+    /// family.get_or_create(&vec![("method".to_owned(), "GET".to_owned())]).inc();
+    ///
+    /// // Clear the family of all label sets.
+    /// family.clear();
+    /// ```
+    pub fn clear(&self) {
+        self.metrics.write().clear()
+    }
+
     pub(crate) fn read(&self) -> RwLockReadGuard<HashMap<S, M>> {
         self.metrics.read()
     }
@@ -295,4 +336,87 @@ mod tests {
         let custom_builder = CustomBuilder { custom_start: 1.0 };
         Family::<(), Histogram, CustomBuilder>::new_with_constructor(custom_builder);
     }
+
+    #[test]
+    fn counter_family_remove() {
+        let family = Family::<Vec<(String, String)>, Counter>::default();
+
+        family
+            .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+            .inc();
+
+        assert_eq!(
+            1,
+            family
+                .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+                .get()
+        );
+
+        family
+            .get_or_create(&vec![("method".to_string(), "POST".to_string())])
+            .inc_by(2);
+
+        assert_eq!(
+            2,
+            family
+                .get_or_create(&vec![("method".to_string(), "POST".to_string())])
+                .get()
+        );
+
+        // Attempt to remove it twice, showing it really was removed on the
+        // first attempt.
+        assert!(family.remove(&vec![("method".to_string(), "POST".to_string())]));
+        assert!(!family.remove(&vec![("method".to_string(), "POST".to_string())]));
+
+        // This should make a new POST label.
+        family
+            .get_or_create(&vec![("method".to_string(), "POST".to_string())])
+            .inc();
+
+        assert_eq!(
+            1,
+            family
+                .get_or_create(&vec![("method".to_string(), "POST".to_string())])
+                .get()
+        );
+
+        // GET label should have be untouched.
+        assert_eq!(
+            1,
+            family
+                .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+                .get()
+        );
+    }
+
+    #[test]
+    fn counter_family_clear() {
+        let family = Family::<Vec<(String, String)>, Counter>::default();
+
+        // Create a label and check it.
+        family
+            .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+            .inc();
+
+        assert_eq!(
+            1,
+            family
+                .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+                .get()
+        );
+
+        // Clear it, then try recreating and checking it again.
+        family.clear();
+
+        family
+            .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+            .inc();
+
+        assert_eq!(
+            1,
+            family
+                .get_or_create(&vec![("method".to_string(), "GET".to_string())])
+                .get()
+        );
+    }
 }