cpugputpu created HADOOP-16897:
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Summary: Sort fields in ReflectionUtils.java
Key: HADOOP-16897
URL: https://issues.apache.org/jira/browse/HADOOP-16897
Project: Hadoop Common
Issue Type: Bug
Components: util
Reporter: cpugputpu
The tests in
_org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl#testInitFirstVerifyCallBacks_
and
_org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl#testInitFirstVerifyStopInvokedImmediately_
can fail.
java.lang.AssertionError:
Element 0 for metrics
expected:<MetricCounterLong\{info=MetricsInfoImpl{name=C1, description=C1
desc}, value=1}>
but was:<MetricGaugeLong\{info=MetricsInfoImpl{name=G1, description=G1 desc},
value=2}>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:834)
at org.junit.Assert.assertEquals(Assert.java:118)
at org.apache.hadoop.test.MoreAsserts.assertEquals(MoreAsserts.java:60)
at
org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl.checkMetricsRecords(TestMetricsSystemImpl.java:439)
at
org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl.testInitFirstVerifyCallBacks(TestMetricsSystemImpl.java:178)
The root cause of this failure can be analyzed in the following stack trace:
_java.lang.Class.*getDeclaredFields*(Class.java:1916)_
_org.apache.hadoop.util.ReflectionUtils.getDeclaredFieldsIncludingInherited(ReflectionUtils.java:353)_
_org.apache.hadoop.metrics2.lib.MetricsSourceBuilder.<init>(MetricsSourceBuilder.java:68)_
_org.apache.hadoop.metrics2.lib.MetricsAnnotations.newSourceBuilder(MetricsAnnotations.java:43)_
_org.apache.hadoop.metrics2.impl.MetricsSystemImpl.register(MetricsSystemImpl.java:223)_
_org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl.testInitFirstVerifyCallBacks(TestMetricsSystemImpl.java:156)_
The specification about getDeclaredFields() says that "the elements in the
returned array are not sorted and are not in any particular order". The
documentation is here for your reference:
https://docs.oracle.com/javase/8/docs/api/java/lang/Class.html#getDeclaredFields--
And the behaviour might be different for different JVM versions or vendors
The fix is to sort the fields returned by getDeclaredFields() so that the
non-deterministic behaviour can be eliminated completely. In this way, the test
becomes more stable.
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