An information leakage from FileTxnSnapLog to log:

In org.apache.zookeeper.server.persistence.FileTxnSnapLog, the statement LOG.debug don't have LOG controls:
public void processTransaction(TxnHeader hdr,DataTree dt,
Map<Long, Integer> sessions, Record txn)
throws KeeperException.NoNodeException {
......
if (rc.err != Code.OK.intValue())

{ LOG.debug("Ignoring processTxn failure hdr:" + hdr.getType() + ", error: " + rc.err + ", path: " + rc.path); }

......
}

Sensitive information about hdr type or rc path was leaked. The conditional statement LOG.isDebugEnabled() should be added:
public void processTransaction(TxnHeader hdr,DataTree dt,
Map<Long, Integer> sessions, Record txn)
throws KeeperException.NoNodeException {
......
if (rc.err != Code.OK.intValue())

{ if (LOG.isDebugEnabled()) LOG.debug("Ignoring processTxn failure hdr:" + hdr.getType() + ", error: " + rc.err + ", path: " + rc.path); }

......
}