Set<DistributedMember> getAllMembersInDS() {
    InternalCache cache = getCache();
    Set<DistributedMember> distMembers = cache.getDistributedSystem().getAllOtherMembers();
    final Set<DistributedMember> targetedMembers = new HashSet<>();

    // find valid data nodes, i.e non locator, non-admin, non-loner nodes
    for (DistributedMember member : distMembers) {
      InternalDistributedMember idm = (InternalDistributedMember) member;
      if (idm.getVmKind() == ClusterDistributionManager.NORMAL_DM_TYPE) {
        targetedMembers.add(member);
      }
    }
    // Add the local node to list
    targetedMembers.add(cache.getDistributedSystem().getDistributedMember());
    return targetedMembers;
  }
@return if the opValue is CAS then the existingValue; otherwise null
geode-web-api/src/main/java/org/apache/geode/rest/internal/web/controllers/AbstractBaseController.java