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https://issues.apache.org/jira/browse/HIVE-19241?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16475538#comment-16475538
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Alexander Kolbasov commented on HIVE-19241:
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There is a second problem here - since there is no synchronization, we may
incidentally create two thread pools and one of these would never be destroyed
and will never be used.
> HMSHandler initialization isn't thread-safe
> -------------------------------------------
>
> Key: HIVE-19241
> URL: https://issues.apache.org/jira/browse/HIVE-19241
> Project: Hive
> Issue Type: Bug
> Affects Versions: 2.0.2, 3.0.0, 3.1.0
> Reporter: Alexander Kolbasov
> Assignee: Marta Kuczora
> Priority: Major
>
> The code in HMSHandler uses the double-check anti-pattern:
> {code:java}
> public HMSHandler(String name, Configuration conf, boolean init) throws
> MetaException {
> super(name);
> this.conf = conf;
> isInTest = MetastoreConf.getBoolVar(this.conf, ConfVars.HIVE_IN_TEST);
> if (threadPool == null) { // No lock held!!
> synchronized (HMSHandler.class) {
> int numThreads = MetastoreConf.getIntVar(conf,
> ConfVars.FS_HANDLER_THREADS_COUNT);
> threadPool = Executors.newFixedThreadPool(numThreads,
> new ThreadFactoryBuilder().setDaemon(true)
> .setNameFormat("HMSHandler #%d").build());
> }
> }
> {code}
> Notice that the check for threadPool == null isn't protected.
> This means that users of threadPool may see thread pool that isn't completely
> initialized.
> See https://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html
> for a detailed explanation.
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