[SOLR-8908] Registering each ZkIndexSchemaReader as an OnReconnect listener introduces a memory leak

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 5.0, 5.1, 5.2, 5.2.1, 5.3, 5.3.1, 5.4, 5.4.1, 5.5
• Fix Version/s: 5.5.1, 6.0.1, 6.1
• Component/s: Schema and Analysis
• Labels: leak
• Assignee: Timothy Potter
• Reporter: Timothy Potter
• Created: 25/Mar/16 23:59
• Updated: 28/May/16 13:38
• Resolved: 14/Apr/16 18:48

Description

As discovered by Alexey Serba, each ZkIndexSchemaReader registers as an OnReconnect listener with the ZkController to get notified when the ZK Session has been re-established. However, the ZkIndexSchemaReader is never removed from the reconnectListeners list in ZkController when the core is reloaded or removed.

Moreover, it also means that the same core is re-notified of the re-connect more than once if it has been reloaded.

This leads to a memory leak, which can become a real issue if you have a lot of cores or do a lot of reloads of your cores.