Github user tillrohrmann commented on a diff in the pull request: https://github.com/apache/flink/pull/2146#discussion_r68198766 --- Diff: flink-core/src/main/java/org/apache/flink/metrics/groups/TaskManagerJobMetricGroup.java --- @@ -0,0 +1,122 @@ +/* + * 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.groups; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.JobID; +import org.apache.flink.metrics.MetricRegistry; +import org.apache.flink.metrics.groups.scope.ScopeFormat.TaskManagerJobScopeFormat; +import org.apache.flink.util.AbstractID; + +import javax.annotation.Nullable; +import java.util.HashMap; +import java.util.Map; + +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * Special {@link org.apache.flink.metrics.MetricGroup} representing everything belonging to + * a specific job, running on the TaskManager. + * + * <p>Contains extra logic for adding Tasks ({@link TaskMetricGroup}). + */ +@Internal +public class TaskManagerJobMetricGroup extends JobMetricGroup { + + /** The metrics group that contains this group */ + private final TaskManagerMetricGroup parent; + + /** Map from execution attempt ID (task identifier) to task metrics */ + private final Map<AbstractID, TaskMetricGroup> tasks = new HashMap<>(); + + // ------------------------------------------------------------------------ + + public TaskManagerJobMetricGroup( + MetricRegistry registry, + TaskManagerMetricGroup parent, + JobID jobId, + @Nullable String jobName) { + + this(registry, checkNotNull(parent), registry.getScopeFormats().getTaskManagerJobFormat(), jobId, jobName); + } + + public TaskManagerJobMetricGroup( + MetricRegistry registry, + TaskManagerMetricGroup parent, + TaskManagerJobScopeFormat scopeFormat, + JobID jobId, + @Nullable String jobName) { + + super(registry, jobId, jobName, scopeFormat.formatScope(parent, jobId, jobName)); + + this.parent = checkNotNull(parent); + } + + public final TaskManagerMetricGroup parent() { + return parent; + } + + // ------------------------------------------------------------------------ + // adding / removing tasks + // ------------------------------------------------------------------------ + + public TaskMetricGroup addTask( + AbstractID vertexId, + AbstractID executionId, + String taskName, + int subtaskIndex, + int attemptNumber) { + + checkNotNull(executionId); + + synchronized (this) { + if (!isClosed()) { + TaskMetricGroup task = new TaskMetricGroup(registry, this, + vertexId, executionId, taskName, subtaskIndex, attemptNumber); + tasks.put(executionId, task); + return task; + } else { + return null; + } + } + } + + public void removeTaskMetricGroup(AbstractID executionId) { + checkNotNull(executionId); + + boolean removeFromParent = false; + synchronized (this) { + if (!isClosed() && tasks.remove(executionId) != null && tasks.isEmpty()) { + // this call removed the last task. close this group. + removeFromParent = true; + close(); + } + } + + // IMPORTANT: removing from the parent must happen while holding the this group's lock, + // because it would violate the "first parent then subgroup" lock acquisition order --- End diff -- I would assume that it is a typo. The `TaskManagerMetricGroup.removeJobMetricsGroup` does not access the `TaskManagerJobMetricGroup` where it could try to acquire the lock for the task manager job metric group.
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