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https://issues.apache.org/jira/browse/HIVE-16321?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15946045#comment-15946045
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Eugene Koifman commented on HIVE-16321:
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HIVE-13842 could be a workaround for this
> Possible deadlock in metastore with Acid workload
> -------------------------------------------------
>
> Key: HIVE-16321
> URL: https://issues.apache.org/jira/browse/HIVE-16321
> Project: Hive
> Issue Type: Bug
> Components: Transactions
> Affects Versions: 1.3.0
> Reporter: Eugene Koifman
>
> TxnStore.MutexAPI is a mechanism how different Metastore instances can
> coordinate their operations. It uses a JDBCConnection to achieve it.
> In some cases this may lead to deadlock. TxnHandler uses a connection pool
> of fixed size. Suppose you X simultaneous calls to TxnHandlerlock(), where
> X is >= size of the pool. This take all connections form the pool, so when
> {noformat}
> handle = getMutexAPI().acquireLock(MUTEX_KEY.CheckLock.name());
> {noformat}
> is executed in _TxnHandler.checkLock(Connection dbConn, long extLockId)_ the
> pool is empty and the system is deadlocked.
> MutexAPI can't use the same connection as the operation it's protecting.
> (TxnHandler.checkLock(Connection dbConn, long extLockId) is an example).
> We could make MutexAPI use a separate connection pool (size > 'primary' conn
> pool).
> Or we could make TxnHandler.lock(LockRequest rqst) return immediately after
> enqueueing the lock with the expectation that the caller will always follow
> up with a call to checkLock(CheckLockRequest rqst).
> cc [~f1sherox]
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