Martijn Visser created FLINK-41043:
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Summary: NettyShuffleMaster.registerJob fails with "HashMap$Node
cannot be cast to HashMap$TreeNode" when jobs start concurrently
Key: FLINK-41043
URL: https://issues.apache.org/jira/browse/FLINK-41043
Project: Flink
Issue Type: Bug
Components: Runtime / Coordination
Affects Versions: 1.20.6
Reporter: Martijn Visser
https://dev.azure.com/apache-flink/98463496-1af2-4620-8eab-a2ecc1a2e6fe/_build/results?buildId=80031&view=logs&j=0c940707-2659-5648-cbe6-a1ad63045f0a
(release-1.20 nightly 2026-10-11, test_ci table, Java 8)
TimeFunctionsITCase failed 128 of its 350 cases. One JobMaster could not start:
{code}
[ERROR]
org.apache.flink.table.planner.functions.TimeFunctionsITCase.test(TestCase)[301]
-- Time elapsed: 0.492 s <<< ERROR!
java.lang.RuntimeException: Failed to fetch next result
...
Caused by: org.apache.flink.runtime.jobmaster.JobMasterException: Could not
start the JobMaster.
at
org.apache.flink.runtime.jobmaster.JobMaster.onStart(JobMaster.java:462)
...
Caused by: java.lang.ClassCastException: java.util.HashMap$Node cannot be cast
to java.util.HashMap$TreeNode
at
org.apache.flink.runtime.shuffle.NettyShuffleMaster.registerJob(NettyShuffleMaster.java:192)
at
org.apache.flink.runtime.jobmaster.JobMaster.startJobExecution(JobMaster.java:1142)
at
org.apache.flink.runtime.jobmaster.JobMaster.onStart(JobMaster.java:460)
{code}
The other cases failed with "Job completed with illegal application status:
UNKNOWN" (60) and "MiniCluster is not yet running or has already been shut
down" (65).
{{NettyShuffleMaster.jobShuffleContexts}} is a plain {{HashMap}} since
FLINK-33985 (1.20.0). {{registerJob}} and {{unregisterJob}} are called from
each JobMaster's main thread, and the ShuffleMaster is shared by all JobMasters
through {{JobManagerSharedServices}}. {{BuiltInFunctionTestBase}} runs its
cases concurrently against one MiniCluster. The field is the same on
release-2.2, release-2.3 and master. First occurrence.
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