Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/5755#discussion_r177087225
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/jobmaster/factories/DefaultJobManagerJobMetricGroupFactory.java
---
@@ -0,0 +1,46 @@
+/*
+ * 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.jobmaster.factories;
+
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.runtime.jobgraph.JobGraph;
+import org.apache.flink.runtime.metrics.groups.JobManagerJobMetricGroup;
+import org.apache.flink.runtime.metrics.groups.JobManagerMetricGroup;
+
+import javax.annotation.Nonnull;
+
+/**
+ * Implementation of {@link JobManagerJobMetricGroupFactory} which makes
sure that there is always
+ * at most one {@link JobManagerJobMetricGroup} for a given {@link JobID}
registered.
--- End diff --
This comment is misleading as the `JobManagerMetricGroup` already ensures
that at most one group is _registered_.
---
