Chengxin Xu created ZOOKEEPER-4935:
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Summary: Fix potential resource leak
Key: ZOOKEEPER-4935
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-4935
Project: ZooKeeper
Issue Type: Improvement
Components: server
Affects Versions: 3.9.3
Reporter: Chengxin Xu
Fix For: 3.9.3
Attachments: image-2025-06-04-13-13-28-697.png,
image-2025-06-04-13-14-27-680.png, image-2025-06-04-13-26-06-474.png,
image-2025-06-04-13-30-56-580.png
zookeeper-server/src/main/java/org/apache/zookeeper/server/controller/ControllerServerConfig.java#ensureComplete
Any exception occurring before both {{close()}} calls complete successfully can
lead to one or both {{ServerSocket}} instances (and the system ports they hold)
not being released.
The best way to fix this is to use the {{try-with-resources}} statement, which
guarantees that {{Closeable}} resources are closed, even if exceptions occur.
Besides, it seems there are some other leaks I found later, which not methoned
in github issue:
leak2:
org.apache.zookeeper.server.quorum.Learner#validateSession
DataOutputStream dos
if an exception occurs before dos.close(); is reached, dos.close() will be
skipped.
!image-2025-06-04-13-13-28-697.png!
leak3:
org.apache.zookeeper.server.quorum.Learner#request
DataOutputStream oa
if an exception occurs before oa.close(); is reached, oa.close() will be
skipped.
!image-2025-06-04-13-14-27-680.png!
leak 4
org.apache.zookeeper.server.SnapshotComparer#getSnapshot
The code opens snapIS to read from the snapshot file but never explicitly calls
snapIS.close().
!image-2025-06-04-13-26-06-474.png!
leak 5
org.apache.zookeeper.server.TraceFormatter#main FileInputStream、FileChannel
!image-2025-06-04-13-30-56-580.png!
They needs to be explicitly released by calling their close() method.
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