dengzhhu653 commented on code in PR #3817:
URL: https://github.com/apache/hive/pull/3817#discussion_r1037716652
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standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/txn/TxnHandler.java:
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@@ -375,8 +375,13 @@ public void setConf(Configuration conf){
connPool = setupJdbcConnectionPool(conf, maxPoolSize);
}
if (connPoolMutex == null) {
- configurator.resetName("mutex");
- connPoolMutex = setupJdbcConnectionPool(conf, maxPoolSize);
+ // It's kind of a waste to create a fixed size connection pool as
same as the connPool and
+ // the connection pool used in ObjectStore, and the connection pool
is mostly used for MutexAPI that
+ // is primarily designed to provide coarse-grained mutex support to
maintenance tasks running inside
+ // the Metastore, we only use getConnection method to retrieve
connection from this pool,
+ // changing it to NoPoolConnectionPool will make Metastore more
scalable especially
+ // there is a leader in the warehouse.
Review Comment:
> @dengzhhu653 , thank you for the patch. I think this looks like a good
idea overall. I just entered a minor comment about a possible typo.
>
> However, we are also dependent on the connection pool for some other
capabilities. For example, both
[DbCPDataSourceProvider](https://github.com/apache/hive/blob/master/standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/datasource/DbCPDataSourceProvider.java#L103)
and
[HikariCPDataSourceProvider](https://github.com/apache/hive/blob/master/standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/datasource/HikariCPDataSourceProvider.java#L76)
apply a connection timeout. After the switch to `NoPoolConnectionPool`, would
we no longer be enforcing a connection timeout?
Good catch, it makes sense to enforce a connection timeout. Thank you for
the suggestion!
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