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Posted to commits@cassandra.apache.org by "Jeff Jirsa (JIRA)" <ji...@apache.org> on 2017/09/14 23:39:00 UTC
[jira] [Updated] (CASSANDRA-13877) Potential concurrency issue with
CDC size calculation
[ https://issues.apache.org/jira/browse/CASSANDRA-13877?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jeff Jirsa updated CASSANDRA-13877:
-----------------------------------
Description:
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]
was:
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]
> 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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