Github user lvfangmin commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/582#discussion_r207611617
--- Diff: src/java/main/org/apache/zookeeper/metrics/MetricsContext.java ---
@@ -0,0 +1,61 @@
+/**
+ * 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.zookeeper.metrics;
+
+/**
+ * Container of metrics.
+ * Contexts are organized in a hierarchy.
+ */
+public interface MetricsContext {
+
+ /**
+ * Returns a sub context.
+ *
+ * @param name the name of the subcontext
+ *
+ * @return a new metrics context.
+ */
+ MetricsContext getContext(String name);
+
+ /**
+ * Returns a counter.
+ *
+ * @param name
+ * @return the counter identified by name in this context.
+ */
+ Counter getCounter(String name);
+
+ /**
+ * Registers an user provided {@link Gauge} which will be called by
the MetricsProvider in order to sample
+ * an integer value.
+ *
+ * @param name
+ * @param gauge
+ */
+ void registerGauge(String name, Gauge gauge);
--- End diff --
Maybe return boolean to indicate if we successfully registered the gauge or
not. For example, adding an already exist Gauge should return false.
---
