The current log Iterator is used to apply a batch of raft logs to state machine. After the batch is applied to state machine and returns from StateMachine#onApply method, these logs are considered committed.

And while iterating the logs in iterator:

1. We can call Iteartor#setErrorAndRollback to rollback applied logs and halt the state machine.
2. Or call Iteartor#commit to commit the logs already applied.

If we want to commit every log while applying, we should call commit method everytime:

while(it.hasNext()) {
    ByteBuffer data = it.getData();
    // apply data to state machine
   ......
   it.commit();
   it.next();
}

I think we can add an auto-commit mode to simplify the code:

// Enable auto-commit mode
it.setAutoCommit(true);

while(it.hasNext()) {
    ByteBuffer data = it.getData();
    // apply data to state machine
   ......
   it.next();
}

After enabling auto-commit mode by it.setAutoCommit(true), the iterator will call commit automatically when calling hasNext() that returns true.