[CASSANDRA-16119] MockSchema's SSTableReader creation leaks FileHandle and Channel instances

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 4.0-beta3, 4.0
• Component/s: Test/unit
• Bug Category: Correctness - Test Failure
• Severity: Low
• Complexity: Low Hanging Fruit
• Discovered By: Unit Test
• Platform: All
• Since Version: 4.0-beta2

Source Control Link

https://github.com/apache/cassandra/commit/54d297a192ca452dab5640f33fd6c22fd31e2f9c

Test and Documentation Plan

passing unit tests (as this is a change specifically to a unit test helper)

• Assignee: Caleb Rackliffe
• Reporter: Caleb Rackliffe

Authors

Caleb Rackliffe

Reviewers

Marcus Eriksson, Sam Tunnicliffe

• Created: 09/Sep/20 20:56
• Updated: 16/Mar/22 14:15
• Resolved: 10/Sep/20 19:46

Description

MockSchema creates SSTableReader instances for testing, but when it does, it doesn’t seem to ever close the FileHandle and Channel instances from which copies are made for the actual readers. (FileHandle itself also internally copies the channel on creation.) This can trigger leak detection, although perhaps not reliably, from tests like AntiCompactionTest. A couple well-placed try-with-resources blocks should help us avoid this (and shouldn't risk closing anything too early, since the close methods for handles and channels seem only to do reference bookkeeping anyway).

Example:

[junit-timeout] ERROR 16:35:47,747 LEAK DETECTED: a reference (org.apache.cassandra.utils.concurrent.Ref$State@487c0fdb) to class org.apache.cassandra.io.util.FileHandle$Cleanup@2072030898:/var/folders/4d/zfjs7m7s6x5_l93k33r5k6680000gn/T/mocksegmentedfile0tmp was not released before the reference was garbage collected
[junit-timeout] ERROR 16:35:47,747 Allocate trace org.apache.cassandra.utils.concurrent.Ref$State@487c0fdb:
[junit-timeout] Thread[main,5,main]
[junit-timeout] 	at java.lang.Thread.getStackTrace(Thread.java:1559)
[junit-timeout] 	at org.apache.cassandra.utils.concurrent.Ref$Debug.<init>(Ref.java:249)
[junit-timeout] 	at org.apache.cassandra.utils.concurrent.Ref$State.<init>(Ref.java:179)
[junit-timeout] 	at org.apache.cassandra.utils.concurrent.Ref.<init>(Ref.java:101)
[junit-timeout] 	at org.apache.cassandra.utils.concurrent.SharedCloseableImpl.<init>(SharedCloseableImpl.java:30)
[junit-timeout] 	at org.apache.cassandra.io.util.FileHandle.<init>(FileHandle.java:74)
[junit-timeout] 	at org.apache.cassandra.io.util.FileHandle.<init>(FileHandle.java:50)
[junit-timeout] 	at org.apache.cassandra.io.util.FileHandle$Builder.complete(FileHandle.java:389)
[junit-timeout] 	at org.apache.cassandra.schema.MockSchema.sstable(MockSchema.java:124)
[junit-timeout] 	at org.apache.cassandra.schema.MockSchema.sstable(MockSchema.java:83)