[CALCITE-4676] Avatica client leaks TCP connections

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: avatica-1.18.0
• Fix Version/s: avatica-1.19.0
• Component/s: avatica
• Assignee: Istvan Toth
• Reporter: Istvan Toth
• Created: 05/Jul/21 09:15
• Updated: 27/Apr/22 03:24
• Resolved: 08/Jul/21 14:08

Description

The default Http client implmentation uses org.apache.http.impl.conn.PoolingHttpClientConnectionManager to pool connections, and does not close the TCP connections explicitly when the JDBC connection is closed.
However, the http client pools are created per JDBC Connection, so the pooling is effectively only used when concurrent statements are executed from the same Connection object.
This also means that when the application opens and closes a lot of Connections, then every Connection leaves behind active (typically in CLOSE_WAIT) TCP connections, which are only cleaned up on GC.
This wastes resources, and eventually breaks the application, as connection limits are reached.

Issue Links

• is related to: CALCITE-5099 ResultSetEnumerable.enumeratorBasedOnStatement cause the backend connection leak
• links to: Pull Request #149