text: /**
   * 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.
   */
  
  #include "namenode_info.h"
  
  #include "common/util.h"
  #include "common/logging.h"
  
  #include <sstream>
  #include <utility>
  #include <future>
  #include <memory>
  
  namespace hdfs {
  
  ResolvedNamenodeInfo& ResolvedNamenodeInfo::operator=(const NamenodeInfo &info) {
    nameservice = info.nameservice;
    name = info.name;
    uri = info.uri;
    return *this;
  }
  
  
  
  std::string ResolvedNamenodeInfo::str() const {
    std::stringstream ss;
    ss << "ResolvedNamenodeInfo {nameservice: " << nameservice << ", name: " << name << ", uri: " << uri.str();
    ss << ", host: " << uri.get_host();
  
    if(uri.has_port())
      ss << ", port: " << uri.get_port();
    else
      ss << ", invalid port (uninitialized)";
  
    ss << ", scheme: " << uri.get_scheme();
  
    ss << " [";
    for(unsigned int i=0;i<endpoints.size();i++)
      ss << endpoints[i] << " ";
    ss << "] }";
  
    return ss.str();
  }
  
  
  bool ResolveInPlace(::asio::io_service *ioservice, ResolvedNamenodeInfo &info) {
    // this isn't very memory friendly, but if it needs to be called often there are bigger issues at hand
    info.endpoints.clear();
    std::vector<ResolvedNamenodeInfo> resolved = BulkResolve(ioservice, {info});
    if(resolved.size() != 1)
      return false;
  
    info.endpoints = resolved[0].endpoints;
    if(info.endpoints.size() == 0)
      return false;
    return true;
  }
  
  typedef std::vector<asio::ip::tcp::endpoint> endpoint_vector;
  
  // RAII wrapper
  class ScopedResolver {
   private:
    ::asio::io_service *io_service_;
    std::string host_;
    std::string port_;
    ::asio::ip::tcp::resolver::query query_;
    ::asio::ip::tcp::resolver resolver_;
    endpoint_vector endpoints_;
  
    // Caller blocks on access if resolution isn't finished
    std::shared_ptr<std::promise<Status>> result_status_;
   public:
    ScopedResolver(::asio::io_service *service, const std::string &host, const std::string &port) :
          io_service_(service), host_(host), port_(port), query_(host, port), resolver_(*io_service_)
    {
      if(!io_service_)
        LOG_ERROR(kAsyncRuntime, << "ScopedResolver@" << this << " passed nullptr to io_service");
    }
  
    ~ScopedResolver() {
      resolver_.cancel();
    }
  
    bool BeginAsyncResolve() {
      // result_status_ would only exist if this was previously called.  Invalid state.
      if(result_status_) {
        LOG_ERROR(kAsyncRuntime, << "ScopedResolver@" << this << "::BeginAsyncResolve invalid call: may only be called once per instance");
        return false;
      } else if(!io_service_) {
        LOG_ERROR(kAsyncRuntime, << "ScopedResolver@" << this << "::BeginAsyncResolve invalid call: null io_service");
        return false;
      }
  
      // Now set up the promise, set it in async_resolve's callback
      result_status_ = std::make_shared<std::promise<Status>>();
      std::shared_ptr<std::promise<Status>> shared_result = result_status_;
  
      // Callback to pull a copy of endpoints out of resolver and set promise
      auto callback = [this, shared_result](const asio::error_code &ec, ::asio::ip::tcp::resolver::iterator out) {
        if(!ec) {
          std::copy(out, ::asio::ip::tcp::resolver::iterator(), std::back_inserter(endpoints_));
        }
        shared_result->set_value( ToStatus(ec) );
      };
      resolver_.async_resolve(query_, callback);
      return true;
    }
  
    Status Join() {
      if(!result_status_) {
        std::ostringstream errmsg;
        errmsg <<  "ScopedResolver@" << this << "Join invalid call: promise never set";
        return Status::InvalidArgument(errmsg.str().c_str());
      }
  
      std::future<Status> future_result = result_status_->get_future();
      Status res = future_result.get();
      return res;
    }
  
    endpoint_vector GetEndpoints() {
      // Explicitly return by value to decouple lifecycles.
      return endpoints_;
    }
  };
  
  std::vector<ResolvedNamenodeInfo> BulkResolve(::asio::io_service *ioservice, const std::vector<NamenodeInfo> &nodes) {
    std::vector< std::unique_ptr<ScopedResolver> > resolvers;
    resolvers.reserve(nodes.size());
  
    std::vector<ResolvedNamenodeInfo> resolved_info;
    resolved_info.reserve(nodes.size());
  
    for(unsigned int i=0; i<nodes.size(); i++) {
      std::string host = nodes[i].get_host();
      std::string port = nodes[i].get_port();
  
      resolvers.emplace_back(new ScopedResolver(ioservice, host, port));
      resolvers[i]->BeginAsyncResolve();
    }
  
    // Join all async operations
    for(unsigned int i=0; i < resolvers.size(); i++) {
      Status asyncReturnStatus = resolvers[i]->Join();
  
      ResolvedNamenodeInfo info;
      info = nodes[i];
  
      if(asyncReturnStatus.ok()) {
        // Copy out endpoints if things went well
        info.endpoints = resolvers[i]->GetEndpoints();
      } else {
        LOG_ERROR(kAsyncRuntime, << "Unabled to resolve endpoints for host: " << nodes[i].get_host()
                                                                 << " port: " << nodes[i].get_port());
      }
  
      resolved_info.push_back(info);
    }
    return resolved_info;
  }
  
  }
  