Mrhs121 opened a new pull request, #17526:
URL: https://github.com/apache/dolphinscheduler/pull/17526
<!--Thanks very much for contributing to Apache DolphinScheduler, we are
happy that you want to help us improve DolphinScheduler! -->
## Purpose of the pull request
An NPE error is thrown when starting the master.
```
[WI-0][TI-0] - 2025-09-21 03:24:47.217 INFO [Master-Server]
o.a.d.s.m.c.ClusterManager:[93] - Initialized WorkerClusters: [ ]
[WI-0][TI-0] - 2025-09-21 03:24:47.218 ERROR [Curator-TreeCache-0]
o.a.c.f.r.c.TreeCache:[828] -
java.lang.NullPointerException: null
at
org.apache.dolphinscheduler.plugin.registry.zookeeper.ZookeeperTreeCacheListenerAdapter.childEvent(ZookeeperTreeCacheListenerAdapter.java:42)
at
org.apache.curator.framework.recipes.cache.TreeCache.lambda$callListeners$1(TreeCache.java:811)
at
org.apache.curator.framework.listen.MappingListenerManager.lambda$forEach$0(MappingListenerManager.java:92)
at
org.apache.curator.framework.listen.MappingListenerManager.forEach(MappingListenerManager.java:89)
at
org.apache.curator.framework.listen.StandardListenerManager.forEach(StandardListenerManager.java:89)
at
org.apache.curator.framework.recipes.cache.TreeCache.callListeners(TreeCache.java:807)
at
org.apache.curator.framework.recipes.cache.TreeCache.access$1900(TreeCache.java:79)
at
org.apache.curator.framework.recipes.cache.TreeCache$2.run(TreeCache.java:909)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)
[WI-0][TI-0] - 2025-09-21 03:24:47.219 INFO [Curator-TreeCache-0]
o.a.d.s.m.c.AbstractClusterSubscribeListener:[41] - Server
MasterServerMetadata(super=BaseServerMetadata(processId=46421,
serverStartupTime=1758396285183, address=10.1.2.10:5678,
cpuUsage=0.435457953936797, memoryUsage=0.6507625579833984,
serverStatus=NORMAL)) added
[WI-0][TI-0] - 2025-09-21 03:24:47.219 ERROR [Curator-TreeCache-0]
o.a.c.f.r.c.TreeCache:[828] -
java.lang.NullPointerException: null
at
org.apache.dolphinscheduler.plugin.registry.zookeeper.ZookeeperTreeCacheListenerAdapter.childEvent(ZookeeperTreeCacheListenerAdapter.java:42)
at
org.apache.curator.framework.recipes.cache.TreeCache.lambda$callListeners$1(TreeCache.java:811)
at
org.apache.curator.framework.listen.MappingListenerManager.lambda$forEach$0(MappingListenerManager.java:92)
at
org.apache.curator.framework.listen.MappingListenerManager.forEach(MappingListenerManager.java:89)
at
org.apache.curator.framework.listen.StandardListenerManager.forEach(StandardListenerManager.java:89)
at
org.apache.curator.framework.recipes.cache.TreeCache.callListeners(TreeCache.java:807)
at
org.apache.curator.framework.recipes.cache.TreeCache.access$1900(TreeCache.java:79)
at
org.apache.curator.framework.recipes.cache.TreeCache$2.run(TreeCache.java:909)
at
java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:750)
[WI-0][TI-0] - 2025-09-21 03:24:47.288 INFO [Master-Server]
o.a.d.s.m.c.ClusterManager:[59] - ClusterManager started...
[WI-0][TI-0] - 2025-09-21 03:24:47.290 INFO [Master-Server]
o.a.d.s.m.c.ClusterStateMonitors:[46] - ClusterStateMonitors started...
[WI-0][TI-0] - 2025-09-21 03:24:47.513 INFO [Master-Server]
o.a.d.s.m.e.WorkflowEventBusFireWorkers:[71] - WorkflowEventBusFireWorkers s
```
First, let me explain why NPE is thrown. From the source code of curator
below, you can see that when the event is of the following four
types(INITIALIZED or CONNECTION_SUSPENDED or CONNECTION_LOST or
CONNECTION_RECONNECTED), the data in event is null by default. Dolphin does not
handle the null value of data, so npe is thrown
https://github.com/apache/dolphinscheduler/blob/b5e73983933f054d738ddb8d48d5818254bd369b/dolphinscheduler-registry/dolphinscheduler-registry-plugins/dolphinscheduler-registry-zookeeper/src/main/java/org/apache/dolphinscheduler/plugin/registry/zookeeper/ZookeeperTreeCacheListenerAdapter.java#L42
<img width="969" height="214" alt="截屏2025-09-21 03 36 50"
src="https://github.com/user-attachments/assets/e70c12c0-788b-407e-84ad-c6d76eb910b9";
/>
<img width="716" height="106" alt="截屏2025-09-21 03 36 38"
src="https://github.com/user-attachments/assets/985cedf5-b8a5-4ecc-847f-d1b7b68cc36a";
/>
Curator only logs the error message, so the NPE doesn’t break master
startup; nevertheless, we should still eliminate the misleading stack-trace to
avoid confusing users.
<img width="796" height="279" alt="截屏2025-09-21 03 35 06"
src="https://github.com/user-attachments/assets/746f8016-228f-4244-a290-56592179698b";
/>
<img width="806" height="452" alt="截屏2025-09-21 03 34 50"
src="https://github.com/user-attachments/assets/5ff9a146-619a-43da-8db6-d8698f836652";
/>
<!--(For example: This pull request adds checkstyle plugin).-->
## Brief change log
<!--*(for example:)*
- *Add maven-checkstyle-plugin to root pom.xml*
-->
## Verify this pull request
<!--*(Please pick either of the following options)*-->
This pull request is code cleanup without any test coverage.
*(or)*
This pull request is already covered by existing tests, such as *(please
describe tests)*.
(or)
This change added tests and can be verified as follows:
<!--*(example:)*
- *Added dolphinscheduler-dao tests for end-to-end.*
- *Added CronUtilsTest to verify the change.*
- *Manually verified the change by testing locally.* -->
(or)
## Pull Request Notice
[Pull Request
Notice](https://github.com/apache/dolphinscheduler/blob/dev/docs/docs/en/contribute/join/pull-request.md)
If your pull request contains incompatible change, you should also add it to
`docs/docs/en/guide/upgrade/incompatible.md`
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