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
36namespace boost {
37
38BOOST_LOG_OPEN_NAMESPACE
39
40namespace 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 */
50class block_on_overflow
51{
52#ifndef BOOST_LOG_DOXYGEN_PASS
53private:
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
73private:
74 //! Blocked threads
75 thread_contexts m_thread_contexts;
76
77public:
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(value&: 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
141BOOST_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_
148

source code of boost/libs/log/include/boost/log/sinks/block_on_overflow.hpp