ERROR - An error occurred. java.lang.IllegalArgumentException: Comparison method violates its general contract
Problem
The following error log message is observed in the hivemq.log when using 4.30 or 4.28.3
ERROR - An error occurred.
java.lang.IllegalArgumentException: Comparison method violates its general contract!
at java.base/java.util.TimSort.mergeHi(TimSort.java:903)
at java.base/java.util.TimSort.mergeAt(TimSort.java:520)
at java.base/java.util.TimSort.mergeForceCollapse(TimSort.java:461)
at java.base/java.util.TimSort.sort(TimSort.java:254)
at java.base/java.util.Arrays.sort(Arrays.java:1234)
at com.google.common.collect.ImmutableList.sortedCopyOf(Source.java:348)
at hmq.nj.f.a(Source.java:61)
at hmq.nj.c.f(Source.java:206)
at hmq.nj.c.e(Source.java:188)
at java.base/java.lang.Thread.run(Thread.java:1583
Solution
Ignore the error message.
The issue should be fixed in HiveMQ v.4.31