Yu-Wen Lai created HIVE-25113:
---------------------------------
Summary: 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
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}
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
