void bringInstanceUp(String instanceName) {
    for (MockHelixAdmin helixAdmin : helixAdmins.values()) {
      if (helixAdmin.getInstancesInCluster(clusterName).contains(instanceName)) {
        helixAdmin.bringInstanceUp(instanceName);
      }
    }
    if (isAggregatedViewUsed) {
      localHelixAdmin.triggerLiveInstanceChangeNotification();
    } else {
      helixAdmins.values().forEach(MockHelixAdmin::triggerLiveInstanceChangeNotification);
    }
  }
Bring the given instance up.
@param instanceName the instance to be brought up.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixCluster.java