Github user yanghua commented on a diff in the pull request:
https://github.com/apache/flink/pull/6292#discussion_r201313023
--- Diff:
flink-runtime/src/test/java/org/apache/flink/runtime/metrics/util/InterceptingTaskMetricGroup.java
---
@@ -0,0 +1,53 @@
+/*
+ * 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.runtime.metrics.util;
+
+import org.apache.flink.metrics.Metric;
+import org.apache.flink.runtime.metrics.groups.TaskMetricGroup;
+import org.apache.flink.runtime.metrics.groups.UnregisteredMetricGroups;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * A {@link TaskMetricGroup} that exposes all registered metrics.
+ */
+public class InterceptingTaskMetricGroup extends
UnregisteredMetricGroups.UnregisteredTaskMetricGroup {
+
+ private Map<String, Metric> intercepted;
+
+ /**
+ * Returns the registered metric for the given name, or null if it was
never registered.
+ *
+ * @param name metric name
+ * @return registered metric for the given name, or null if it was
never registered
+ */
+ public Metric get(String name) {
+ return intercepted.get(name);
--- End diff --
if this method is invoked before `addMetric` , then the `intercepted`
would not be initialized, seems it can trigger NPE
---
