ceph/src/boost/libs/log/include/boost/log/sinks/block_on_overflow.hpp

   1 /*
   2  *          Copyright Andrey Semashev 2007 - 2015.
   3  * Distributed under the Boost Software License, Version 1.0.
   4  *    (See accompanying file LICENSE_1_0.txt or copy at
   5  *          http://www.boost.org/LICENSE_1_0.txt)
   6  */
   7 /*!
   8  * \file   block_on_overflow.hpp
   9  * \author Andrey Semashev
  10  * \date   04.01.2012
  11  *
  12  * The header contains implementation of \c block_on_overflow strategy for handling
  13  * queue overflows in bounded queues for the asynchronous sink frontend.
  14  */
  15
  16 #ifndef BOOST_LOG_SINKS_BLOCK_ON_OVERFLOW_HPP_INCLUDED_
  17 #define BOOST_LOG_SINKS_BLOCK_ON_OVERFLOW_HPP_INCLUDED_
  18
  19 #include <boost/log/detail/config.hpp>
  20
  21 #ifdef BOOST_HAS_PRAGMA_ONCE
  22 #pragma once
  23 #endif
  24
  25 #if defined(BOOST_LOG_NO_THREADS)
  26 #error Boost.Log: This header content is only supported in multithreaded environment
  27 #endif
  28
  29 #include <boost/intrusive/options.hpp>
  30 #include <boost/intrusive/list.hpp>
  31 #include <boost/intrusive/list_hook.hpp>
  32 #include <boost/thread/condition_variable.hpp>
  33 #include <boost/log/core/record_view.hpp>
  34 #include <boost/log/detail/header.hpp>
  35
  36 namespace boost {
  37
  38 BOOST_LOG_OPEN_NAMESPACE
  39
  40 namespace sinks {
  41
  42 /*!
  43  * \brief Blocking strategy for handling log record queue overflows
  44  *
  45  * This strategy will cause enqueueing threads to block when the
  46  * log record queue overflows. The blocked threads will be woken as
  47  * soon as there appears free space in the queue, in the same order
  48  * they attempted to enqueue records.
  49  */
  50 class block_on_overflow
  51 {
  52 #ifndef BOOST_LOG_DOXYGEN_PASS
  53 private:
  54     typedef intrusive::list_base_hook<
  55         intrusive::link_mode< intrusive::auto_unlink >
  56     > thread_context_hook_t;
  57
  58     struct thread_context :
  59         public thread_context_hook_t
  60     {
  61         condition_variable cond;
  62         bool result;
  63
  64         thread_context() : result(true) {}
  65     };
  66
  67     typedef intrusive::list<
  68         thread_context,
  69         intrusive::base_hook< thread_context_hook_t >,
  70         intrusive::constant_time_size< false >
  71     > thread_contexts;
  72
  73 private:
  74     //! Blocked threads
  75     thread_contexts m_thread_contexts;
  76
  77 public:
  78     /*!
  79      * Default constructor.
  80      */
  81     BOOST_DEFAULTED_FUNCTION(block_on_overflow(), {})
  82
  83     /*!
  84      * This method is called by the queue when overflow is detected.
  85      *
  86      * \param lock An internal lock that protects the queue
  87      *
  88      * \retval true Attempt to enqueue the record again.
  89      * \retval false Discard the record.
  90      */
  91     template< typename LockT >
  92     bool on_overflow(record_view const&, LockT& lock)
  93     {
  94         thread_context context;
  95         m_thread_contexts.push_back(context);
  96         do
  97         {
  98             context.cond.wait(lock);
  99         }
 100         while (context.is_linked());
 101
 102         return context.result;
 103     }
 104
 105     /*!
 106      * This method is called by the queue when there appears a free space.
 107      * The internal lock protecting the queue is locked when calling this method.
 108      */
 109     void on_queue_space_available()
 110     {
 111         if (!m_thread_contexts.empty())
 112         {
 113             m_thread_contexts.front().cond.notify_one();
 114             m_thread_contexts.pop_front();
 115         }
 116     }
 117
 118     /*!
 119      * This method is called by the queue to interrupt any possible waits in \c on_overflow.
 120      * The internal lock protecting the queue is locked when calling this method.
 121      */
 122     void interrupt()
 123     {
 124         while (!m_thread_contexts.empty())
 125         {
 126             thread_context& context = m_thread_contexts.front();
 127             context.result = false;
 128             context.cond.notify_one();
 129             m_thread_contexts.pop_front();
 130         }
 131     }
 132
 133     //  Copying prohibited
 134     BOOST_DELETED_FUNCTION(block_on_overflow(block_on_overflow const&))
 135     BOOST_DELETED_FUNCTION(block_on_overflow& operator= (block_on_overflow const&))
 136 #endif // BOOST_LOG_DOXYGEN_PASS
 137 };
 138
 139 } // namespace sinks
 140
 141 BOOST_LOG_CLOSE_NAMESPACE // namespace log
 142
 143 } // namespace boost
 144
 145 #include <boost/log/detail/footer.hpp>
 146
 147 #endif // BOOST_LOG_SINKS_BLOCK_ON_OVERFLOW_HPP_INCLUDED_