nef_one_thread/pub.cpp

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/*
  SObjectizer 5.
*/
 
/*!
 * \file
 * \brief Functions for creating and binding of the single thread dispatcher
 * that provides noexcept guarantee for scheduling evt_finish demand.
 *
 * \since v.5.5.8
 */
 
#include <so_5/disp/nef_one_thread/pub.hpp>
 
#include <so_5/disp/reuse/actual_work_thread_factory_to_use.hpp>
#include <so_5/disp/reuse/data_source_prefix_helpers.hpp>
#include <so_5/disp/reuse/make_actual_dispatcher.hpp>
 
#include <so_5/impl/thread_join_stuff.hpp>
 
#include <so_5/stats/repository.hpp>
#include <so_5/stats/messages.hpp>
#include <so_5/stats/std_names.hpp>
 
#include <so_5/send_functions.hpp>
 
namespace so_5 {
 
namespace disp {
 
namespace nef_one_thread {
 
namespace impl {
 
namespace queue_traits = so_5::disp::mpsc_queue_traits;
 
namespace stats = so_5::stats;
 
//
// demand_t
//
/*!
 * \brief A single execution demand.
 *
 * \since v.5.8.0
 */
struct demand_t
  {
    //! Execution demand to be used.
    /*!
     * \note
     * It may be empty (if the default constructor was used for
     * preallocated evt_start/evt_finish demands).
     */
    execution_demand_t m_execution_demand;
 
    //! Next demand in the queue.
    /*!
     * \note
     * It's a dynamically allocated object that has to be deallocated
     * manually during the destruction of the queue.
     */
    demand_t * m_next = nullptr;
 
    /*!
     * \brief Default constructor.
     *
     * It's necessary for preallocation of evt_start and evt_finish
     * demands.
     */
    demand_t() = default;
 
    //! Initializing constructor.
    demand_t( execution_demand_t && source )
      : m_execution_demand{ std::move( source ) }
      {}
  };
 
//
// demand_unique_ptr_t
//
/*!
 * \brief An alias for unique_ptr to demand.
 *
 * \since v.5.8.0
 */
using demand_unique_ptr_t = std::unique_ptr< demand_t >;
 
//
// demand_queue_t
//
class demand_queue_t
  {
    //! Queue lock.
    queue_traits::lock_unique_ptr_t m_lock;
 
    //! Shutdown flag.
    bool m_shutdown = false;
 
    //! Head of the queue.
    /*! Null if queue is empty. */
    demand_t * m_head = nullptr;
    //! Tail of the queue.
    /*! Null if queue is empty. */
    demand_t * m_tail = nullptr;
 
    //! Current size of the queue.
    std::atomic< std::size_t > m_size = { 0 };
 
  public:
    //! Initializing constructor.
    demand_queue_t(
      //! Lock to be used for queue protection.
      queue_traits::lock_unique_ptr_t lock )
      : m_lock{ std::move(lock) }
      {}
 
    ~demand_queue_t() noexcept
      {
        while( m_head )
          {
            remove_head();
          }
      }
 
    //! Set the shutdown signal.
    void
    stop()
      {
        queue_traits::lock_guard_t lock{ *m_lock };
 
        m_shutdown = true;
 
        // If the queue is empty then someone can wait a notification.
        if( !m_head )
          {
            lock.notify_one();
          }
      }
 
    void
    push( demand_unique_ptr_t tail_demand )
      {
        queue_traits::lock_guard_t lock{ *m_lock };
 
        ++m_size;
 
        if( nullptr == m_head )
          {
            m_head = tail_demand.release();
            m_tail = m_head;
 
            // Someone might wait for the first demand.
            lock.notify_one();
          }
        else
          {
            m_tail->m_next = tail_demand.release();
            m_tail = m_tail->m_next;
          }
      }
 
    // Returns nullptr if shutdown flag is set.
    demand_unique_ptr_t
    pop()
      {
        demand_unique_ptr_t result;
 
        queue_traits::unique_lock_t lock{ *m_lock };
 
        while( !m_shutdown && (nullptr == m_head) )
          {
            lock.wait_for_notify();
          }
 
        if( !m_shutdown )
          {
            // Assume that m_head != nullptr.
            result = remove_head();
          }
 
        return result;
      }
 
    //! Get the current size of the queue.
    std::size_t
    size() const
      {
        return m_size.load( std::memory_order_acquire );
      }
 
  private:
    //! Helper method for deleting queue's head object.
    demand_unique_ptr_t
    remove_head() noexcept
      {
        demand_unique_ptr_t to_be_deleted{ m_head };
        m_head = m_head->m_next;
        to_be_deleted->m_next = nullptr;
 
        --m_size;
 
        return to_be_deleted;
      }
  };
 
//
// agent_queue_t
//
/*!
 *
 * \note
 * This class is Moveable, but not Copyable.
 */
class agent_queue_t final : public event_queue_t
  {
    std::reference_wrapper< demand_queue_t > m_dest_queue;
 
    demand_unique_ptr_t m_evt_start_demand;
    demand_unique_ptr_t m_evt_finish_demand;
 
  public:
    agent_queue_t(
      demand_queue_t & dest_queue,
      demand_unique_ptr_t evt_start_demand,
      demand_unique_ptr_t evt_finish_demand )
      : m_dest_queue{ dest_queue }
      , m_evt_start_demand{ std::move(evt_start_demand) }
      , m_evt_finish_demand{ std::move(evt_finish_demand) }
      {}
 
    agent_queue_t( const agent_queue_t & ) = delete;
    agent_queue_t &
    operator=( const agent_queue_t & ) = delete;
 
    agent_queue_t( agent_queue_t && o ) = delete;
    agent_queue_t &
    operator=( agent_queue_t && o ) = delete;
 
    void
    push( execution_demand_t demand ) override
      {
        m_dest_queue.get().push(
            std::make_unique< demand_t >( std::move(demand) ) );
      }
 
    void
    push_evt_start( execution_demand_t demand ) override
      {
        // ATTENTION: assume that m_evt_start_demand is valid.
        // It's UB is that isn't the true.
        m_evt_start_demand->m_execution_demand = std::move(demand);
        m_dest_queue.get().push( std::move(m_evt_start_demand) );
      }
 
    void
    push_evt_finish( execution_demand_t demand ) noexcept override
      {
        // ATTENTION: assume that m_evt_start_demand is valid.
        // It's UB is that isn't the true.
        //
        // Don't expect exceptions here.
        m_evt_finish_demand->m_execution_demand = std::move(demand);
        m_dest_queue.get().push( std::move(m_evt_finish_demand) );
      }
  };
 
namespace work_thread_details {
 
//
// common_data_t
//
/*!
 * \brief A common data for all work thread implementations.
 *
 * \since v.5.8.0
 */
struct common_data_t
  {
    //! Demands queue to work for.
    demand_queue_t m_queue;
 
    //! Thread object.
    work_thread_holder_t m_thread_holder;
 
    //! ID of the work thread.
    /*!
     * \note Receives actual value only after successful start
     * of the thread.
     */
    so_5::current_thread_id_t m_thread_id;
 
    //! Initializing constructor.
    common_data_t(
      //! Lock to be used for queue protection.
      queue_traits::lock_unique_ptr_t lock,
      //! Worker thread to be used.
      work_thread_holder_t thread_holder )
      : m_queue{ std::move(lock) }
      , m_thread_holder{ std::move(thread_holder) }
      {}
  };
 
//
// no_activity_tracking_impl_t
//
/*!
 * \brief A part of implementation of work thread without activity tracking.
 *
 * \since v.5.8.0
 */
class no_activity_tracking_impl_t : protected common_data_t
  {
  public :
    no_activity_tracking_impl_t(
      //! Lock to be used for queue protection.
      queue_traits::lock_unique_ptr_t lock,
      //! Worker thread to be used.
      work_thread_holder_t thread_holder )
      : common_data_t{
          std::move(lock),
          std::move(thread_holder)
        }
      {}
 
  protected :
    void
    work_started() { /* Nothing to do. */ }
 
    void
    work_finished() { /* Nothing to do. */ }
 
    void
    wait_started() { /* Nothing to do. */ }
 
    void
    wait_finished() { /* Nothing to do. */ }
  };
 
//
// with_activity_tracking_impl_t
//
/*!
 * \brief A part of implementation of work thread with activity tracking.
 *
 * \since v.5.5.18
 */
class with_activity_tracking_impl_t : protected common_data_t
  {
  public :
    with_activity_tracking_impl_t(
      //! Lock to be used for queue protection.
      queue_traits::lock_unique_ptr_t lock,
      //! Worker thread to be used.
      work_thread_holder_t thread_holder )
      : common_data_t{
          std::move(lock),
          std::move(thread_holder)
        }
      {}
 
    so_5::stats::work_thread_activity_stats_t
    take_activity_stats()
      {
        so_5::stats::work_thread_activity_stats_t result;
 
        result.m_working_stats = m_working_stats.take_stats();
        result.m_waiting_stats = m_waiting_stats.take_stats();
 
        return result;
      }
 
  protected :
    //! Statictics for work activity.
    so_5::stats::activity_tracking_stuff::stats_collector_t<
        so_5::stats::activity_tracking_stuff::internal_lock >
      m_working_stats;
 
    //! Statictics for wait activity.
    so_5::stats::activity_tracking_stuff::stats_collector_t<
        so_5::stats::activity_tracking_stuff::internal_lock >
      m_waiting_stats;
 
    void
    work_started() { m_working_stats.start(); }
 
    void
    work_finished() { m_working_stats.stop(); }
 
    void
    wait_started() { m_waiting_stats.start(); }
 
    void
    wait_finished() { m_waiting_stats.stop(); }
  };
 
} /* namespace work_thread_details */
 
//
// work_thread_template_t
//
/*!
 * \brief A worker thread for nef_one_thread dispatcher.
 *
 * \since v.5.8.0
 */
template< typename Work_Thread >
class work_thread_template_t : public Work_Thread
  {
    using base_type_t = Work_Thread;
 
  public :
    //! Initializing constructor.
    work_thread_template_t(
      //! Lock to be used for queue protection.
      queue_traits::lock_unique_ptr_t lock,
      //! Worker thread to be used.
      work_thread_holder_t thread_holder )
      : base_type_t{
          std::move(lock),
          std::move(thread_holder)
        }
      {}
 
    void
    start()
      {
        this->m_thread_holder.unchecked_get().start( [this]() { body(); } );
      }
 
    void
    stop()
      {
        this->m_queue.stop();
      }
 
    void
    join()
      {
        so_5::impl::ensure_join_from_different_thread( this->m_thread_id );
        this->m_thread_holder.unchecked_get().join();
      }
 
    [[nodiscard]]
    so_5::current_thread_id_t
    thread_id() const
      {
        return this->m_thread_id;
      }
 
    [[nodiscard]]
    demand_queue_t &
    demand_queue() noexcept
      {
        return this->m_queue;
      }
 
  private :
    void
    body()
      {
        this->m_thread_id = so_5::query_current_thread_id();
 
        bool demand_extracted = true;
        do
          {
            auto d = this->pop_demand();
            if( d )
              {
                this->call_handler( d->m_execution_demand );
              }
            else
              // No more demands, it's time to break the loop.
              demand_extracted = false;
          }
        while( demand_extracted );
      }
 
    [[nodiscard]]
    demand_unique_ptr_t
    pop_demand()
      {
        this->wait_started();
        auto wait_meter_stopper = so_5::details::at_scope_exit(
            [this] { this->wait_finished(); } );
 
        return this->m_queue.pop();
      }
 
    void
    call_handler( so_5::execution_demand_t & demand )
      {
        this->work_started();
        auto work_meter_stopper = so_5::details::at_scope_exit(
            [this] { this->work_finished(); } );
 
        demand.call_handler( this->m_thread_id );
      }
  };
 
//
// work_thread_no_activity_tracking_t
//
using work_thread_no_activity_tracking_t =
  work_thread_template_t< work_thread_details::no_activity_tracking_impl_t >;
 
//
// work_thread_with_activity_tracking_t
//
using work_thread_with_activity_tracking_t =
  work_thread_template_t< work_thread_details::with_activity_tracking_impl_t >;
 
//
// send_thread_activity_stats
//
void
send_thread_activity_stats(
  const so_5::mbox_t &,
  const stats::prefix_t &,
  work_thread_no_activity_tracking_t & )
  {
    /* Nothing to do */
  }
 
void
send_thread_activity_stats(
  const so_5::mbox_t & mbox,
  const stats::prefix_t & prefix,
  work_thread_with_activity_tracking_t & wt )
  {
    so_5::send< stats::messages::work_thread_activity >(
        mbox,
        prefix,
        stats::suffixes::work_thread_activity(),
        wt.thread_id(),
        wt.take_activity_stats() );
  }
 
//
// dispatcher_template_t
//
/*!
 * \brief An implementation of dispatcher with one working
 * thread and guarantee that evt_finish demands will be added to
 * the queue without exceptions.
 *
 * \since v.5.8.0
 */
template< typename Work_Thread >
class dispatcher_template_t final : public disp_binder_t
  {
    friend class disp_data_source_t;
 
  public:
    dispatcher_template_t(
      outliving_reference_t< environment_t > env,
      const std::string_view name_base,
      disp_params_t params )
      : m_work_thread{
          params.queue_params().lock_factory()(),
          so_5::disp::reuse::acquire_work_thread( params, env.get() ),
        }
      , m_data_source{
          outliving_mutable(env.get().stats_repository()),
          name_base,
          outliving_mutable(*this)
        }
      {
        m_work_thread.start();
      }
 
    ~dispatcher_template_t() noexcept override
      {
        m_work_thread.stop();
        m_work_thread.join();
      }
 
    void
    preallocate_resources(
      agent_t & agent ) override
      {
        // Assume that there is no pointer to the agent in the map yet.
        auto evt_start_demand = std::make_unique< demand_t >();
        auto evt_finish_demand = std::make_unique< demand_t >();
 
        auto queue = std::make_unique< agent_queue_t >(
            m_work_thread.demand_queue(),
            std::move(evt_start_demand),
            std::move(evt_finish_demand)
          );
 
        // All further operattions have to be performed under the lock.
        std::lock_guard< std::mutex > lock{ m_agent_map_lock };
 
        m_agents.emplace(
            std::addressof(agent),
            std::move(queue) );
      }
 
    void
    undo_preallocation(
      agent_t & agent ) noexcept override
      {
        std::lock_guard< std::mutex > lock{ m_agent_map_lock };
 
        m_agents.erase( std::addressof(agent) );
      }
 
    void
    bind(
      agent_t & agent ) noexcept override
      {
        event_queue_t & queue = [&]() -> event_queue_t &
          {
            std::lock_guard< std::mutex > lock{ m_agent_map_lock };
 
            auto it = m_agents.find( std::addressof(agent) );
            // Just in case, to simplify debugging if something
            // went very, very wrong.
            // This will lead to the termination of the application,
            // but it is better than accessing a random pointer.
            if( it == m_agents.end() )
              SO_5_THROW_EXCEPTION(
                  rc_no_preallocated_resources_for_agent,
                  "nef_one_thread dispatcher has no info about an agent "
                  "in bind() method" );
 
            return *(it->second);
          }();
 
        agent.so_bind_to_dispatcher( queue );
      }
 
    void
    unbind(
      agent_t & agent ) noexcept override
      {
        // Just reuse existing implementation.
        this->undo_preallocation( agent );
      }
 
  private:
    /*!
     * \brief Data source for run-time monitoring of whole dispatcher.
     *
     * \since v.5.8.0
     */
    class disp_data_source_t : public stats::source_t
      {
        //! Dispatcher to work with.
        outliving_reference_t< dispatcher_template_t > m_dispatcher;
 
        //! Basic prefix for data sources.
        stats::prefix_t m_base_prefix;
 
      public :
        disp_data_source_t(
          const std::string_view name_base,
          outliving_reference_t< dispatcher_template_t > disp )
          : m_dispatcher{ disp }
          , m_base_prefix{ so_5::disp::reuse::make_disp_prefix(
                "nef-ot",
                name_base,
                &(disp.get()) )
            }
          {}
 
        void
        distribute( const mbox_t & mbox ) override
          {
            auto & disp = m_dispatcher.get();
 
            const std::size_t agents_count = [&disp]() {
                std::lock_guard< std::mutex > lock{ disp.m_agent_map_lock };
                return disp.m_agents.size();
              }();
 
            so_5::send< stats::messages::quantity< std::size_t > >(
                mbox,
                m_base_prefix,
                stats::suffixes::agent_count(),
                agents_count );
 
            so_5::send< stats::messages::quantity< std::size_t > >(
                mbox,
                m_base_prefix,
                stats::suffixes::work_thread_queue_size(),
                disp.m_work_thread.demand_queue().size() );
 
            send_thread_activity_stats(
                mbox,
                m_base_prefix,
                disp.m_work_thread );
          }
      };
 
    //! Type of map from agent pointer to an individual event_queue.
    using agent_map_t = std::map< agent_t *, std::unique_ptr<agent_queue_t> >;
 
    //! Worker thread for the dispatcher.
    Work_Thread m_work_thread;
 
    //! Data source for run-time monitoring.
    stats::auto_registered_source_holder_t< disp_data_source_t >
        m_data_source;
 
    //! Lock for agent_map protection.
    std::mutex m_agent_map_lock;
 
    //! Agents for those resources are allocated by the dispatcher.
    agent_map_t m_agents;
  };
 
//
// dispatcher_handle_maker_t
//
class dispatcher_handle_maker_t
  {
  public :
    static dispatcher_handle_t
    make( disp_binder_shptr_t binder ) noexcept
      {
        return { std::move( binder ) };
      }
  };
 
} /* namespace impl */
 
//
// make_dispatcher
//
SO_5_FUNC dispatcher_handle_t
make_dispatcher(
  environment_t & env,
  const std::string_view data_sources_name_base,
  disp_params_t params )
  {
    using namespace so_5::disp::reuse;
 
    using dispatcher_no_activity_tracking_t =
        impl::dispatcher_template_t<
            impl::work_thread_no_activity_tracking_t >;
 
    using dispatcher_with_activity_tracking_t =
        impl::dispatcher_template_t<
            impl::work_thread_with_activity_tracking_t >;
 
    disp_binder_shptr_t binder = so_5::disp::reuse::make_actual_dispatcher<
            disp_binder_t,
            dispatcher_no_activity_tracking_t,
            dispatcher_with_activity_tracking_t >(
        outliving_mutable(env),
        data_sources_name_base,
        std::move(params) );
 
    return impl::dispatcher_handle_maker_t::make( std::move(binder) );
  }
 
} /* namespace nef_one_thread */
 
} /* namespace disp */
 
} /* namespace so_5 */