private static void throwInvalidReplicationFactorIfZero(int numUnfenced) {
        if (numUnfenced == 0) {
            throw new InvalidReplicationFactorException("All brokers are currently fenced.");
        }
    }
The offset we use to determine which rack is returned first.
metadata/src/main/java/org/apache/kafka/metadata/placement/StripedReplicaPlacer.java