nodelet_lazy.h

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/* Author: Ryohei Ueda, Kentaro Wada <www.kentaro.wada@gmail.com>
 */

#ifndef NODELET_LAZY_H_
#define NODELET_LAZY_H_

#include <ros/ros.h>
#include <nodelet/nodelet.h>
#include <boost/thread.hpp>
#include <string>
#include <vector>

namespace nodelet_topic_tools
{

enum ConnectionStatus
{
  NOT_INITIALIZED,
  NOT_SUBSCRIBED,
  SUBSCRIBED
};

class NodeletLazy: public nodelet::Nodelet
{
public:
  NodeletLazy() {}

protected:
  virtual void onInit()
  {
    connection_status_ = NOT_SUBSCRIBED;
    bool use_multithread;
    ros::param::param<bool>("~use_multithread_callback", use_multithread, true);
    if (use_multithread)
    {
      NODELET_DEBUG("Using multithread callback");
      nh_.reset (new ros::NodeHandle(getMTNodeHandle()));
      pnh_.reset (new ros::NodeHandle(getMTPrivateNodeHandle()));
    }
    else
    {
      NODELET_DEBUG("Using singlethread callback");
      nh_.reset(new ros::NodeHandle(getNodeHandle()));
      pnh_.reset(new ros::NodeHandle(getPrivateNodeHandle()));
    }
    // option to use lazy transport
    pnh_->param("lazy", lazy_, true);
    // option for logging about being subscribed
    pnh_->param("verbose_connection", verbose_connection_, false);
    if (!verbose_connection_)
    {
      nh_->param("verbose_connection", verbose_connection_, false);
    }
    // timer to warn when no connection in the specified seconds
    ever_subscribed_ = false;
    double duration_to_warn_no_connection;
    pnh_->param("duration_to_warn_no_connection",
                duration_to_warn_no_connection, 5.0);
    if (duration_to_warn_no_connection > 0)
    {
      timer_ever_subscribed_ = nh_->createWallTimer(
        ros::WallDuration(duration_to_warn_no_connection),
        &NodeletLazy::warnNeverSubscribedCallback,
        this,
        /*oneshot=*/true);
    }
  }

  virtual void onInitPostProcess()
  {
    if (!lazy_)
    {
      boost::mutex::scoped_lock lock(connection_mutex_);
      subscribe();
      ever_subscribed_ = true;
    }
  }

  virtual void connectionCallback(const ros::SingleSubscriberPublisher& pub)
  {
    if (verbose_connection_)
    {
      NODELET_INFO("New connection or disconnection is detected");
    }
    if (lazy_)
    {
      boost::mutex::scoped_lock lock(connection_mutex_);
      for (size_t i = 0; i < publishers_.size(); i++)
      {
        ros::Publisher pub = publishers_[i];
        if (pub.getNumSubscribers() > 0)
        {
          if (connection_status_ != SUBSCRIBED)
          {
            if (verbose_connection_)
            {
              NODELET_INFO("Subscribe input topics");
            }
            subscribe();
            connection_status_ = SUBSCRIBED;
          }
          if (!ever_subscribed_)
          {
            ever_subscribed_ = true;
          }
          return;
        }
      }
      if (connection_status_ == SUBSCRIBED)
      {
        if (verbose_connection_)
        {
          NODELET_INFO("Unsubscribe input topics");
        }
        unsubscribe();
        connection_status_ = NOT_SUBSCRIBED;
      }
    }
  }

  virtual void warnNeverSubscribedCallback(const ros::WallTimerEvent& event)
  {
    if (!ever_subscribed_)
    {
      NODELET_WARN("This node/nodelet subscribes topics only when subscribed.");
    }
  }


  virtual void subscribe() = 0;

  virtual void unsubscribe() = 0;

  template<class T> ros::Publisher
  advertise(ros::NodeHandle& nh,
            std::string topic, int queue_size, bool latch=false)
  {
    boost::mutex::scoped_lock lock(connection_mutex_);
    ros::SubscriberStatusCallback connect_cb
      = boost::bind(&NodeletLazy::connectionCallback, this, _1);
    ros::SubscriberStatusCallback disconnect_cb
      = boost::bind(&NodeletLazy::connectionCallback, this, _1);
    ros::Publisher pub = nh.advertise<T>(topic, queue_size,
                                          connect_cb,
                                          disconnect_cb,
                                          ros::VoidConstPtr(),
                                          latch);
    publishers_.push_back(pub);
    return pub;
  }

  boost::mutex connection_mutex_;

  boost::shared_ptr<ros::NodeHandle> nh_;

  boost::shared_ptr<ros::NodeHandle> pnh_;

  std::vector<ros::Publisher> publishers_;

  ros::WallTimer timer_ever_subscribed_;

  bool ever_subscribed_;

  bool lazy_;

  ConnectionStatus connection_status_;

  bool verbose_connection_;

private:
};

}  // namespace nodelet_topic_tools

#endif  // NODELET_LAZY_H_