rkhachatryan commented on a change in pull request #17757: URL: https://github.com/apache/flink/pull/17757#discussion_r750487411
########## File path: flink-dstl/flink-dstl-dfs/src/main/java/org/apache/flink/changelog/fs/ChangelogStorageMetricGroup.java ########## @@ -0,0 +1,134 @@ +/* + * 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.changelog.fs; + +import org.apache.flink.metrics.Counter; +import org.apache.flink.metrics.Gauge; +import org.apache.flink.metrics.Histogram; +import org.apache.flink.metrics.MetricGroup; +import org.apache.flink.runtime.metrics.DescriptiveStatisticsHistogram; +import org.apache.flink.runtime.metrics.groups.ProxyMetricGroup; + +import javax.annotation.concurrent.ThreadSafe; + +import java.util.concurrent.atomic.LongAdder; + +/** + * Metrics related to the Changelog Storage used by the Changelog State Backend. Thread-safety is + * required because it is used by multiple uploader threads. + */ +@ThreadSafe Review comment: Exactly, Thread-safety is required because it is used by multiple uploader threads. Let me clarify first: - existing metric **groups** are thread-safe (though they don't have to be, just by convention) - the metrics they register are usually not (depends on the implementation, e.g. histogram is thread-safe) Now, the existing metrics are usually updated by one thread and read by another, so in the worst case results will be delayed. But here, metrics are **updated** by multiple threads; so results could be corrupted if not thread-safe. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
