be/src/kudu/util/net/dns_resolver.h

// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.
#ifndef KUDU_UTIL_NET_DNS_RESOLVER_H
#define KUDU_UTIL_NET_DNS_RESOLVER_H

#include <vector>

#include "kudu/gutil/gscoped_ptr.h"
#include "kudu/gutil/macros.h"
#include "kudu/util/status_callback.h"

namespace kudu {

class HostPort;
class Sockaddr;
class ThreadPool;

// DNS Resolver which supports async address resolution.
class DnsResolver {
 public:
  DnsResolver();
  ~DnsResolver();

  // Resolve any addresses corresponding to this host:port pair.
  // Note that a host may resolve to more than one IP address.
  //
  // 'addresses' may be NULL, in which case this function simply checks that
  // the host/port pair can be resolved, without returning anything.
  //
  // When the result is available, or an error occurred, 'cb' is called
  // with the result Status.
  //
  // NOTE: the callback should be fast since it is called by the DNS
  // resolution thread.
  // NOTE: in some rare cases, the callback may also be called inline
  // from this function call, on the caller's thread.
  void ResolveAddresses(const HostPort& hostport,
                        std::vector<Sockaddr>* addresses,
                        const StatusCallback& cb);

 private:
  gscoped_ptr<ThreadPool> pool_;

  DISALLOW_COPY_AND_ASSIGN(DnsResolver);
};

} // namespace kudu
#endif /* KUDU_UTIL_NET_DNS_RESOLVER_H */