[ZOOKEEPER-4804] Use daemon threads for Netty client

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.8.3
• Fix Version/s: 3.10.0, 3.9.3
• Labels: pull-request-available
• Assignee: Istvan Toth
• Reporter: Istvan Toth
• Created: 08/Feb/24 07:56
• Updated: 24/Oct/24 20:09
• Resolved: 09/Mar/24 05:32

Description

When the Netty client is used, the Java process hangs on System.exit if there is an open Zookeeper connection.

This is caused by the non-daemon threads created by Netty.

Exiting without closing the connection is not a good practice, but this hang does not happen with the NIO client, and I think ZK should behave the same regardless of the client implementation used.

The Netty ThreadFactory implementation is configurable, it shouldn't be too hard make sure that daemon threads are created.

Issue Links

• causes: HBASE-28353 Close HBase connection on implicit exit from HBase shell
• causes: PHOENIX-7223 Make Sure Tools Always Close HBase Connections on Exit
• is related to: HBASE-28448 CompressionTest hangs when run over a Ozone ofs path
• links to: GitHub Pull Request #2142
• links to: GitHub Pull Request #2150