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https://issues.apache.org/jira/browse/HIVE-25113?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yu-Wen Lai resolved HIVE-25113.
-------------------------------
Resolution: Fixed
> Connection starvation in TxnHandler.getValidWriteIds
> ----------------------------------------------------
>
> Key: HIVE-25113
> URL: https://issues.apache.org/jira/browse/HIVE-25113
> Project: Hive
> Issue Type: Bug
> Components: Transactions
> Reporter: Yu-Wen Lai
> Assignee: Yu-Wen Lai
> Priority: Major
> Labels: pull-request-available
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
>
> The current code looks like below.
> {code:java}
> dbConn = getDbConn(Connection.TRANSACTION_READ_COMMITTED);
> validTxnList = TxnUtils.createValidReadTxnList(getOpenTxns(), 0);
> {code}
> In the function getOpenTxns, it will request another connection from pool.
> That is, this thread already held a connection, however, it would request for
> another connection. When there are more than 10 (default connection pool
> size) simultaneous getValidWriteIds requests, it can cause a starvation
> problem. In that situation, each thread holds a connection and waits for
> another connection. Then, we will see the following exception after timeout.
> {code:java}
> metastore.RetryingHMSHandler: MetaException(message:Unable to select from
> transaction database, java.sql.SQLTransientConnectionException: HikariPool-3
> - Connection is not available, request timed out after 30000ms.{code}
>
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