private DistributedMember getDistributedMember(String memberName) {
    Set<DistributedMember> locators = new HashSet<>(
        cache.getDistributionManager().getAllHostedLocatorsWithSharedConfiguration().keySet());
    return locators.stream()
        .filter(x -> x.getId().equals(memberName))
        .findFirst()
        .orElse(null);
  }
*
CacheListener on ConfigRegion on Locators to write the configuration changes to file-system.
geode-core/src/main/java/org/apache/geode/management/internal/configuration/callbacks/ConfigurationChangeListener.java