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Posted to commits@cassandra.apache.org by "Simon Zhou (JIRA)" <ji...@apache.org> on 2017/09/14 23:32:00 UTC
[jira] [Created] (CASSANDRA-13877) Potential concurrency issue with
CDC size calculation
Simon Zhou created CASSANDRA-13877:
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Summary: Potential concurrency issue with CDC size calculation
Key: CASSANDRA-13877
URL: https://issues.apache.org/jira/browse/CASSANDRA-13877
Project: Cassandra
Issue Type: Bug
Reporter: Simon Zhou
Assignee: Simon Zhou
We're backporting CDC feature and bug fixes to 3.0. There is potential visibility issue with two variables CDCSizeTracker.sizeInProgress and DirectorySizeCalculator.size. They're declared as volatile however there are cases that when assigning new values to them, the new values depend on the current value. For example:
https://github.com/apache/cassandra/blob/e9da85723a8dd40872c4bca087a03b655bd2cacb/src/java/org/apache/cassandra/db/commitlog/CommitLogSegmentManagerCDC.java#L285
https://github.com/apache/cassandra/blob/e9da85723a8dd40872c4bca087a03b655bd2cacb/src/java/org/apache/cassandra/db/commitlog/CommitLogSegmentManagerCDC.java#L297
In rare cases we'll not be able to calculate CDC data size correctly. We should change these two variables back to AtomicLong, as the simplest fix. Java Concurrency In Practice section 3.1.3 explains well why we shouldn't use volatile in these two cases. I'll provide patch shortly.
cc [~JoshuaMcKenzie] [~jay.zhuang]
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