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)