private void generateLagOverrides(long base, long upperBound) {
    replicationManager.lagOverrides = new HashMap<>();
    for (PartitionId partitionId : clusterMap.getAllPartitionIds(null)) {
      for (ReplicaId replicaId : partitionId.getReplicaIds()) {
        String key = MockReplicationManager.getPartitionLagKey(partitionId, replicaId.getDataNodeId().getHostname(),
            replicaId.getReplicaPath());
        Long value = base + Utils.getRandomLong(TestUtils.RANDOM, upperBound - base + 1);
        replicationManager.lagOverrides.put(key, value);
      }
    }
  }
Generates lag overrides in {@code replicationManager} with each lag a number between {@code base} and
{@code upperBound} both inclusive.
@param base the minimum value of lag (inclusive)
@param upperBound the maximum value of lag (inclusive)
ambry-server/src/test/java/com/github/ambry/server/AmbryServerRequestsTest.java