Aihua Xu created HIVE-13149:
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Summary: Remove some unnecessary HMS connections from HS2
Key: HIVE-13149
URL: https://issues.apache.org/jira/browse/HIVE-13149
Project: Hive
Issue Type: Sub-task
Components: HiveServer2
Affects Versions: 2.0.0
Reporter: Aihua Xu
Assignee: Aihua Xu
In SessionState class, currently we will always try to get a HMS connection in
{{start(SessionState startSs, boolean isAsync, LogHelper console)}} regardless
of if the connection will be used later or not.
When SessionState is accessed by the tasks in TaskRunner.java, although most of
the tasks other than some of them like StatsTask, don't need to access HMS,
currently a new HMS connection will be established for each thread. If
HiveServer2 is configured to run in parallel and the query involves many tasks,
then the connections are created but unused.
{noformat}
@Override
public void run() {
runner = Thread.currentThread();
try {
OperationLog.setCurrentOperationLog(operationLog);
SessionState.start(ss);
runSequential();
{noformat}
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