Set<DistributedMember> getAllServers() {
    return cache.getDistributionManager().getNormalDistributionManagerIds()
        .stream().map(DistributedMember.class::cast).collect(Collectors.toSet());
  }
find members within these groups

@param includeLocators whether to include locators in this search or not
geode-core/src/main/java/org/apache/geode/management/internal/configuration/validators/MemberValidator.java