[GitHub] [cassandra] smiklosovic commented on a change in pull request #1160: CASSANDRA-16721 Move RepairedDataInfo to the execution controller rather than the ReadCommand to avoid unintended sharing

[GitBox <gi...@apache.org>]

smiklosovic commented on a change in pull request #1160:
URL: https://github.com/apache/cassandra/pull/1160#discussion_r693054226



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File path: test/distributed/org/apache/cassandra/distributed/test/RepairDigestTrackingTest.java
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@@ -340,6 +347,99 @@ else if (ccAfterPartitionRead != ccBefore)
         }
     }
 
+    /**
+     * In CASSANDRA-16721, we discovered that if responses from remote replicas came back while the local runnable was 
+     * still executing, the fact that {@link ReadCommand} was mutable meant that the trackRepairedStatus flag on the
+     * command instance could move from false to true in executeLocally(), between setting the 
+     * RepairedDataInfo/gathering the sstables and calling extend(). When this happened, the RDI was still the 
+     * stand-in object NO_OP_REPAIRED_DATA_INFO, which has a null repairedDataCounter, and we hit the NPE.
+     * 
+     * Similarly, the trackRepairedStatus flag could be set after the point at which the RDI is set on the local 
+     * read, assigned to the repairedDataInfo in {@link ReadCommand}, and improperly shared between initial local read
+     * and the local read triggered by read repair.
+     * 
+     * These problems are now sidestepped completely by CASSANDRA-16721, as an RDI instance is ow created and destroyed 

Review comment:
       ow -> now




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