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From uromahn <>
Subject Re: Potential Bug in Master-Slave with Replicated LevelDB Store
Date Tue, 21 Oct 2014 10:07:37 GMT
Quick update:

I have enabled G1GC for the JVM running the broker and since then had no
problem again. The master broker stays master even under very heavy load.

So, my suggestion and recommendation when using replicated LevelDB would be
to use the G1 garbage collector significantly reducing "stop-the-world" GCs
causing a time-out on the connection to Zookeeper which will ultimately
"demote" a broker to Slave without real reason.

However, while running my tests, I noticed the following "Warnings" in the
log files of both slaves:
2014-10-21 09:44:37,694 | WARN  | Invalid log position: 1569963680 |
org.apache.activemq.leveldb.LevelDBClient | Thread-2

There are probably hundreds of those (didn't actually count them) with
obviously changing log positions.

I will retry my tests by switching to the Java implementation of LevelDB.

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