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https://issues.apache.org/jira/browse/SOLR-9030?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15258560#comment-15258560
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Scott Blum commented on SOLR-9030:
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The final keyword conveys special thread-safety semantics in the JMM.
https://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.5
I don't know that this is actually the bug, but because DocCollection
initializes znodeVersion to -1 before subsequently setting it to the 'correct'
value, it's not out of the question that this could expose a data race that
marking the field 'final' would have prevented. We should make that change
anyway. Here's another description with a code example:
http://www.cs.umd.edu/~pugh/java/memoryModel/jsr-133-faq.html#finalRight
I don't think "effectively final" has any special meaning for instance fields;
the compiler can infer that local variables are effectively final through
static analysis, but the compiler can't know whether or not you might modify a
non-final instance field via reflection.
> The 'downnode' command can trip asserts in ZkStateWriter or cause
> BadVersionException in Overseer
> -------------------------------------------------------------------------------------------------
>
> Key: SOLR-9030
> URL: https://issues.apache.org/jira/browse/SOLR-9030
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Reporter: Shalin Shekhar Mangar
> Fix For: master, 6.1
>
>
> While working on SOLR-9014 I came across a strange test failure.
> {code}
> [junit4] ERROR 16.9s |
> AsyncCallRequestStatusResponseTest.testAsyncCallStatusResponse <<<
> [junit4] > Throwable #1:
> com.carrotsearch.randomizedtesting.UncaughtExceptionError: Captured an
> uncaught exception in thread: Thread[id=46,
> name=OverseerStateUpdate-95769832112259076-127.0.0.1:51135_z_oeg%2Ft-n_0000000000,
> state=RUNNABLE, group=Overseer state updater.]
> [junit4] > at
> __randomizedtesting.SeedInfo.seed([91F68DA7E10807C3:CBF7E84BCF328A1A]:0)
> [junit4] > Caused by: java.lang.AssertionError
> [junit4] > at
> __randomizedtesting.SeedInfo.seed([91F68DA7E10807C3]:0)
> [junit4] > at
> org.apache.solr.cloud.overseer.ZkStateWriter.writePendingUpdates(ZkStateWriter.java:231)
> [junit4] > at
> org.apache.solr.cloud.Overseer$ClusterStateUpdater.run(Overseer.java:240)
> [junit4] > at java.lang.Thread.run(Thread.java:745)
> {code}
> The underlying problem can manifest by tripping the above assert or a
> BadVersionException as well. I found that this was introduced in SOLR-7281
> where a new 'downnode' command was added.
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