You are viewing a plain text version of this content. The canonical link for it is here.
Posted to dev@kylin.apache.org by "cpugputpu (Jira)" <ji...@apache.org> on 2020/03/02 14:00:00 UTC
[jira] [Created] (KYLIN-4397) Use newLinkedHashMap in
stream-coordinator/src/main/java/org/apache/kylin/stream/coordinator/assign/AssignmentUtil.java
cpugputpu created KYLIN-4397:
--------------------------------
Summary: Use newLinkedHashMap in stream-coordinator/src/main/java/org/apache/kylin/stream/coordinator/assign/AssignmentUtil.java
Key: KYLIN-4397
URL: https://issues.apache.org/jira/browse/KYLIN-4397
Project: Kylin
Issue Type: Bug
Reporter: cpugputpu
The tests in _org.apache.kylin.stream.coordinator.assign.DefaultAssignerTest#reBalanceTest_ can fail and the failure is presented as follow.
_java.lang.AssertionError: expected:<2> but was:<1>_
_at org.apache.kylin.stream.coordinator.assign.DefaultAssignerTest.reBalanceTest(DefaultAssignerTest.java:165)_ when executing _assertEquals(2, rsAssignment.size());_
The root cause of this failure is when executing _Map<Integer, Map<String, List<Partition>>> result = assigner.reBalancePlan(rsList, cubes, existingAssignments);_ it will iterate over a HashMap. The stack trace is here:
_java.util.HashMap$EntrySet.iterator(HashMap.java:1014)
org.apache.kylin.stream.coordinator.assign.DefaultAssigner.reBalancePlan(DefaultAssigner.java:93)
org.apache.kylin.stream.coordinator.assign.DefaultAssignerTest.reBalanceTest(DefaultAssignerTest.java:163)_
The specification about HashMap says that "this class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time". The documentation is here for your reference: [https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.htm|https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html][l|https://docs.oracle.com/javase/8/docs/api/java/util/HashMap.html]
The fix is to use LinkedHashMap instead of HashMap when initializing a Map. In this way, the non-deterministic behaviour is eliminated and the test will not suffer from the failure again. The code will be more stable.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)