Time Synchronization

For best results, you should synchronize the clocks used by all machines in a replication group. If you are using a time-based consistency policy, this is an absolute requirement (see Time Consistency Policies for more information). Time synchronization is easily achieved using a mechanism like NTPD.

In addition, time synchronization is also a requirement for internal JE HA bookkeeping. For example, JE checks for clock skew between the Master and a Replica when the Replica performs its startup handshake with the Master. This handshake will abort and throw EnvironmentFailureException if the clock skew between the two machines is greater than the value set for the MAX_CLOCK_DELTA property. This property can be set using the ReplicationConfig.setMaxClockDelta() method, or in the JE configuration file using the je.rep.maxClockDelta property.

Finally, well synchronized clocks make it easier to correlate events in the logging output from different nodes in the group.