Github user StephanEwen commented on a diff in the pull request:
https://github.com/apache/flink/pull/5501#discussion_r173146575
--- Diff:
flink-metrics/flink-metrics-core/src/main/java/org/apache/flink/metrics/NumberGauge.java
---
@@ -0,0 +1,26 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.metrics;
+
+/**
+ * A NumberGauge is a {@link Metric} that calculates a specific {@link
Number} value at a point in time.
+ */
+public interface NumberGauge extends Metric {
--- End diff --
Should be annotated with `@FunctionalInterface` to guard that this always
stays lambda-able.
Also annotate with Public / PublicEvolving?
---
