The dataDir and dataLogDir are used opposingly

_emphasized text_After upgrading from zookeeper 3.4.5, to 3.4.11, without editing zoo.cfg, the new version of the server tries to use the dataDir as the dataLogDir, and the dataLogDir as the dataDir. Or at least some parts of the server.

Configuration file has:

$ grep -i data /etc/zookeeper/zoo.cfg 
dataLogDir=/var/lib/zookeeper/datalog
dataDir=/var/lib/zookeeper/data

But runtime configuration has:

$ echo conf | nc localhost 2181 | grep -i data
dataDir=/var/lib/zookeeper/datalog/version-2
dataLogDir=/var/lib/zookeeper/data/version-2

Also, I got this in the debug logs, so clearly some parts of the server confuse things.

[PurgeTask:FileTxnSnapLog@79] - Opening datadir:/var/lib/zookeeper/datalog snapDir:/var/lib/zookeeper/data
[main:FileTxnSnapLog@79] - Opening datadir:/var/lib/zookeeper/data snapDir:/var/lib/zookeeper/datalog

I tried to look in the code for wrong uses of the directories. I only found ZookeeperServer.java is passing the arguments to FileTxnSnapLog in the wrong order, but the code comment says that this is legacy only for tests, so I assume it isn't the cause for my case.