/usr/include/spdlog/details/async_log_helper.h is in libspdlog-dev 1:0.16.3-1.
This file is owned by root:root, with mode 0o644.
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// Copyright(c) 2015 Gabi Melman.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)
//
// async log helper :
// Process logs asynchronously using a back thread.
//
// If the internal queue of log messages reaches its max size,
// then the client call will block until there is more room.
//
#pragma once
#include "../common.h"
#include "../sinks/sink.h"
#include "../details/mpmc_bounded_q.h"
#include "../details/log_msg.h"
#include "../details/os.h"
#include "../formatter.h"
#include <chrono>
#include <exception>
#include <functional>
#include <memory>
#include <string>
#include <thread>
#include <utility>
#include <vector>
namespace spdlog
{
namespace details
{
class async_log_helper
{
// Async msg to move to/from the queue
// Movable only. should never be copied
enum class async_msg_type
{
log,
flush,
terminate
};
struct async_msg
{
std::string logger_name;
level::level_enum level;
log_clock::time_point time;
size_t thread_id;
std::string txt;
async_msg_type msg_type;
size_t msg_id;
async_msg() = default;
~async_msg() = default;
async_msg(async_msg&& other) SPDLOG_NOEXCEPT:
logger_name(std::move(other.logger_name)),
level(std::move(other.level)),
time(std::move(other.time)),
thread_id(other.thread_id),
txt(std::move(other.txt)),
msg_type(std::move(other.msg_type)),
msg_id(other.msg_id)
{}
async_msg(async_msg_type m_type):
level(level::info),
thread_id(0),
msg_type(m_type),
msg_id(0)
{}
async_msg& operator=(async_msg&& other) SPDLOG_NOEXCEPT
{
logger_name = std::move(other.logger_name);
level = other.level;
time = std::move(other.time);
thread_id = other.thread_id;
txt = std::move(other.txt);
msg_type = other.msg_type;
msg_id = other.msg_id;
return *this;
}
// never copy or assign. should only be moved..
async_msg(const async_msg&) = delete;
async_msg& operator=(const async_msg& other) = delete;
// construct from log_msg
async_msg(const details::log_msg& m):
level(m.level),
time(m.time),
thread_id(m.thread_id),
txt(m.raw.data(), m.raw.size()),
msg_type(async_msg_type::log),
msg_id(m.msg_id)
{
#ifndef SPDLOG_NO_NAME
logger_name = *m.logger_name;
#endif
}
// copy into log_msg
void fill_log_msg(log_msg &msg)
{
msg.logger_name = &logger_name;
msg.level = level;
msg.time = time;
msg.thread_id = thread_id;
msg.raw << txt;
msg.msg_id = msg_id;
}
};
public:
using item_type = async_msg;
using q_type = details::mpmc_bounded_queue<item_type>;
using clock = std::chrono::steady_clock;
async_log_helper(formatter_ptr formatter,
const std::vector<sink_ptr>& sinks,
size_t queue_size,
const log_err_handler err_handler,
const async_overflow_policy overflow_policy = async_overflow_policy::block_retry,
const std::function<void()>& worker_warmup_cb = nullptr,
const std::chrono::milliseconds& flush_interval_ms = std::chrono::milliseconds::zero(),
const std::function<void()>& worker_teardown_cb = nullptr);
void log(const details::log_msg& msg);
// stop logging and join the back thread
~async_log_helper();
void set_formatter(formatter_ptr);
void flush(bool wait_for_q);
void set_error_handler(spdlog::log_err_handler err_handler);
private:
formatter_ptr _formatter;
std::vector<std::shared_ptr<sinks::sink>> _sinks;
// queue of messages to log
q_type _q;
log_err_handler _err_handler;
bool _flush_requested;
bool _terminate_requested;
// overflow policy
const async_overflow_policy _overflow_policy;
// worker thread warmup callback - one can set thread priority, affinity, etc
const std::function<void()> _worker_warmup_cb;
// auto periodic sink flush parameter
const std::chrono::milliseconds _flush_interval_ms;
// worker thread teardown callback
const std::function<void()> _worker_teardown_cb;
// worker thread
std::thread _worker_thread;
void push_msg(async_msg&& new_msg);
// worker thread main loop
void worker_loop();
// pop next message from the queue and process it. will set the last_pop to the pop time
// return false if termination of the queue is required
bool process_next_msg(log_clock::time_point& last_pop, log_clock::time_point& last_flush);
void handle_flush_interval(log_clock::time_point& now, log_clock::time_point& last_flush);
// sleep,yield or return immediately using the time passed since last message as a hint
static void sleep_or_yield(const spdlog::log_clock::time_point& now, const log_clock::time_point& last_op_time);
// wait until the queue is empty
void wait_empty_q();
};
}
}
///////////////////////////////////////////////////////////////////////////////
// async_sink class implementation
///////////////////////////////////////////////////////////////////////////////
inline spdlog::details::async_log_helper::async_log_helper(
formatter_ptr formatter,
const std::vector<sink_ptr>& sinks,
size_t queue_size,
log_err_handler err_handler,
const async_overflow_policy overflow_policy,
const std::function<void()>& worker_warmup_cb,
const std::chrono::milliseconds& flush_interval_ms,
const std::function<void()>& worker_teardown_cb):
_formatter(formatter),
_sinks(sinks),
_q(queue_size),
_err_handler(err_handler),
_flush_requested(false),
_terminate_requested(false),
_overflow_policy(overflow_policy),
_worker_warmup_cb(worker_warmup_cb),
_flush_interval_ms(flush_interval_ms),
_worker_teardown_cb(worker_teardown_cb),
_worker_thread(&async_log_helper::worker_loop, this)
{}
// Send to the worker thread termination message(level=off)
// and wait for it to finish gracefully
inline spdlog::details::async_log_helper::~async_log_helper()
{
try
{
push_msg(async_msg(async_msg_type::terminate));
_worker_thread.join();
}
catch (...) // don't crash in destructor
{
}
}
//Try to push and block until succeeded (if the policy is not to discard when the queue is full)
inline void spdlog::details::async_log_helper::log(const details::log_msg& msg)
{
push_msg(async_msg(msg));
}
inline void spdlog::details::async_log_helper::push_msg(details::async_log_helper::async_msg&& new_msg)
{
if (!_q.enqueue(std::move(new_msg)) && _overflow_policy != async_overflow_policy::discard_log_msg)
{
auto last_op_time = details::os::now();
auto now = last_op_time;
do
{
now = details::os::now();
sleep_or_yield(now, last_op_time);
}
while (!_q.enqueue(std::move(new_msg)));
}
}
// optionally wait for the queue be empty and request flush from the sinks
inline void spdlog::details::async_log_helper::flush(bool wait_for_q)
{
push_msg(async_msg(async_msg_type::flush));
if (wait_for_q)
wait_empty_q(); //return when queue is empty
}
inline void spdlog::details::async_log_helper::worker_loop()
{
if (_worker_warmup_cb) _worker_warmup_cb();
auto last_pop = details::os::now();
auto last_flush = last_pop;
auto active = true;
while (active)
{
try
{
active = process_next_msg(last_pop, last_flush);
}
catch (const std::exception &ex)
{
_err_handler(ex.what());
}
catch(...)
{
_err_handler("Unknown exeption in async logger worker loop.");
}
}
if (_worker_teardown_cb) _worker_teardown_cb();
}
// process next message in the queue
// return true if this thread should still be active (while no terminate msg was received)
inline bool spdlog::details::async_log_helper::process_next_msg(log_clock::time_point& last_pop, log_clock::time_point& last_flush)
{
async_msg incoming_async_msg;
if (_q.dequeue(incoming_async_msg))
{
last_pop = details::os::now();
switch (incoming_async_msg.msg_type)
{
case async_msg_type::flush:
_flush_requested = true;
break;
case async_msg_type::terminate:
_flush_requested = true;
_terminate_requested = true;
break;
default:
log_msg incoming_log_msg;
incoming_async_msg.fill_log_msg(incoming_log_msg);
_formatter->format(incoming_log_msg);
for (auto &s : _sinks)
{
if (s->should_log(incoming_log_msg.level))
{
s->log(incoming_log_msg);
}
}
}
return true;
}
// Handle empty queue..
// This is the only place where the queue can terminate or flush to avoid losing messages already in the queue
else
{
auto now = details::os::now();
handle_flush_interval(now, last_flush);
sleep_or_yield(now, last_pop);
return !_terminate_requested;
}
}
// flush all sinks if _flush_interval_ms has expired
inline void spdlog::details::async_log_helper::handle_flush_interval(log_clock::time_point& now, log_clock::time_point& last_flush)
{
auto should_flush = _flush_requested || (_flush_interval_ms != std::chrono::milliseconds::zero() && now - last_flush >= _flush_interval_ms);
if (should_flush)
{
for (auto &s : _sinks)
s->flush();
now = last_flush = details::os::now();
_flush_requested = false;
}
}
inline void spdlog::details::async_log_helper::set_formatter(formatter_ptr msg_formatter)
{
_formatter = msg_formatter;
}
// spin, yield or sleep. use the time passed since last message as a hint
inline void spdlog::details::async_log_helper::sleep_or_yield(const spdlog::log_clock::time_point& now, const spdlog::log_clock::time_point& last_op_time)
{
using std::chrono::milliseconds;
using std::chrono::microseconds;
auto time_since_op = now - last_op_time;
// spin upto 50 micros
if (time_since_op <= microseconds(50))
return;
// yield upto 150 micros
if (time_since_op <= microseconds(100))
return std::this_thread::yield();
// sleep for 20 ms upto 200 ms
if (time_since_op <= milliseconds(200))
return details::os::sleep_for_millis(20);
// sleep for 500 ms
return details::os::sleep_for_millis(500);
}
// wait for the queue to be empty
inline void spdlog::details::async_log_helper::wait_empty_q()
{
auto last_op = details::os::now();
while (!_q.is_empty())
{
sleep_or_yield(details::os::now(), last_op);
}
}
inline void spdlog::details::async_log_helper::set_error_handler(spdlog::log_err_handler err_handler)
{
_err_handler = err_handler;
}
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