@Override
  public CompletableFuture<RegionLocations> getMetaRegionLocations() {
    CompletableFuture<RegionLocations> future = new CompletableFuture<>();
    List<HRegionLocation> locs = endpoint.getMetaLocations();
    if (locs.isEmpty()) {
      future.completeExceptionally(new IOException("no meta location available"));
    } else {
      future.complete(new RegionLocations(locs));
    }
    return future;
  }
A {@link ConnectionRegistry} implementation used at server side, where we could use the
{@link ConnectionRegistryEndpoint} directly, without any rpcs.
hbase-server/src/main/java/org/apache/hadoop/hbase/client/ShortCircuitConnectionRegistry.java