@Override
  public CompletableFuture<List<ServerName>> clearDeadServers(List<ServerName> servers) {
    return this.<List<ServerName>> newMasterCaller()
      .action((controller, stub) -> this.<ClearDeadServersRequest, ClearDeadServersResponse,
        List<ServerName>> call(controller, stub,
          RequestConverter.buildClearDeadServersRequest(servers),
          (s, c, req, done) -> s.clearDeadServers(c, req, done),
          (resp) -> ProtobufUtil.toServerNameList(resp.getServerNameList())))
      .call();
  }
Get the region info for the passed region name. The region name may be a full region name or
encoded region name. If the region does not found, then it'll throw an UnknownRegionException
wrapped by a {@link CompletableFuture}
@return region info, wrapped by a {@link CompletableFuture}
hbase-client/src/main/java/org/apache/hadoop/hbase/client/RawAsyncHBaseAdmin.java