muduo网络库学习笔记(三)TimerQueue定时器队列

时间:2023-12-14 15:39:02

muduo网络库学习笔记(三)TimerQueue定时器队列


TimerQueue是EventLoop的组件之一,可以提供定时任务,和周期任务。

本章首先会简述关于timerfd系统定时函数的基本使用,和TimerQueue类的封装结构,最后给出TimerQueue::addTimer()接口的时序图与使用例子.

Linux中的时间函数

·time(2) / time_t(秒)

·ftime(3) / struct timeb(毫秒)

·gettimeofday(2) / struct timeval(微秒)

·clock_gettime(2) / struct timespec(纳秒)

还有gmtime / localtime / timegm / mktime / strftime / struct tm等与当

前时间无关的时间格式转换函数。

定时函数, 用于让程序等待一段时间或安排计划任务:·sleep(3)

·alarm(2)

·usleep(3)

·nanosleep(2)

·clock_nanosleep(2)

·getitimer(2) / setitimer(2)

·timer_create(2) / timer_settime(2) / timer_gettime(2) / timer_delete(2)

·timerfd_create(2) / timerfd_gettime(2) / timerfd_settime(2)

muduo中做的取舍如下

·(计时) 只使用gettimeofday(2)来获取当前时间。

·(定时) 只使用timerfd_*系列函数来处理定时任务。

gettimeofday(2)入选原因(这也是muduo::Timestamp class的主要设计考虑) :

1. time(2)的精度太低, ftime(3)已被废弃; clock_gettime(2)精度最高, 但是其系统调用的开销比gettimeofday(2)大。

2. 在x86-64平台上, gettimeofday(2)不是系统调用, 而是在用户态实现的, 没有上下文切换和陷入内核的开销32。

3. gettimeofday(2)的分辨率(resolution) 是1微秒, 现在的实现确实能达到这个计时精度, 足以满足日常计时的需要。 muduo::Timestamp用一个int64_t来表示从Unix Epoch到现在的微秒数, 其范围可达上下30万年。

timerfd_*入选的原因:

1. sleep(3) / alarm(2) / usleep(3)在实现时有可能用了SIGALRM信号, 在多线程程序中处理信号是个相当麻烦的事情, 应当尽量避免, 再说, 如果主程序和程序库都使用SIGALRM, 就糟糕了。

2. nanosleep(2)和clock_nanosleep(2)是线程安全的, 但是在非阻塞网络编程中, 绝对不能用让线程挂起的方式来等待一段时间, 这样一来程序会失去响应。 正确的做法是注册一个时间回调函数。

3. getitimer(2)和timer_create(2)也是用信号来deliver超时,在多线程程序中也会有麻烦。timer_create(2)可以指定信号的接收方是进程还是线程, 算是一个进步, 不过信号处理函数(signal handler) 能做的事情实在很受限。

4.timerfd_create(2)把时间变成了一个文件描述符, 该“文件”在定时器超时的那一刻变得可读, 这样就能很方便地融入select(2)/poll(2)框架中, 用统一的方式来处理IO事件和超时事件, 这也正是Reactor模式的长处。

5. 传统的Reactor利用select(2)/poll(2)/epoll(4)的timeout来实现定时功能, 但poll(2)和epoll_wait(2)的定时精度只有毫秒,远低于timerfd_settime(2)的定时精度。


timerfd简单使用介绍

本章使用到的两个系统函数:

#include <sys/timerfd.h>
int timerfd_create(int clockid, int flags);
int timerfd_settime(int fd, int flags, const struct itimerspec *new_value,struct itimerspec *old_value);

1、timerfd_create函数生成一个定时器,返回与之关联的文件描述,其中的clockid可以设成CLOCK_REALTIME和CLOCK_MONOTONIC

CLOCK_REALTIME:系统实时时间,随系统实时时间改变而改变,即从UTC1970-1-1 0:0:0开始计时,中间时刻如果系统时间被用户改成其他,则对应的时间相应改变

CLOCK_MONOTONIC:从系统启动这一刻起开始计时,不受系统时间被用户改变的影响

2、timerfd_settime用于启停定时器,new_value为超时时间,old_value为周期性定时时间,为0表示不进行周期性定时.

 struct timespec {
time_t tv_sec; /* Seconds */
long tv_nsec; /* Nanoseconds */
}; struct itimerspec {
struct timespec it_interval; /* Interval for periodic timer */
struct timespec it_value; /* Initial expiration */
};

timerfd示例

通过select 监听timerfd,可读时表明到达定时时间.

#include <sys/timerfd.h>
#include <sys/select.h>
/* According to earlier standards */
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h> int main()
{ int timerfd = ::timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK |TFD_CLOEXEC); struct itimerspec howlong;
bzero(&howlong, sizeof howlong);
howlong.it_value.tv_sec = 3;
timerfd_settime(timerfd, 0, &howlong, NULL); fd_set rdset;
FD_ZERO(&rdset);
FD_SET(timerfd, &rdset); struct timeval timeout;
timeout.tv_sec = 1;
timeout.tv_usec = 0;
while(1)
{
if(select(timerfd + 1, &rdset, NULL, NULL, &timeout) == 0)
{
std::cout << "timeout\n";
timeout.tv_sec = 1;
timeout.tv_usec = 0;
FD_SET(timerfd, &rdset);
continue;
}
std::cout << " timer happend\n";
break;
} close(timerfd); return 0;
} /* print
timeout
timeout
timer happend
*/

muduo中对timerfd的封装

int createTimerfd()
{
int timerfd = ::timerfd_create(CLOCK_MONOTONIC,
TFD_NONBLOCK | TFD_CLOEXEC);
if (timerfd < 0)
{
std::cout << "Failed in timerfd_create" << std::endl;
abort();
}
return timerfd;
} struct timespec howMuchTimeFromNow(TimeStamp when)
{
int64_t microseconds = when.microSecondsSinceEpoch()
- TimeStamp::now().microSecondsSinceEpoch();
if (microseconds < 100)
{
microseconds = 100;
}
struct timespec ts;
ts.tv_sec = static_cast<time_t>(
microseconds / TimeStamp::kMicroSecondsPerSecond);
ts.tv_nsec = static_cast<long>(
(microseconds % TimeStamp::kMicroSecondsPerSecond) * 1000);
return ts;
} void readTimerfd(int timerfd, TimeStamp now)
{
uint64_t howmany;
ssize_t n = ::read(timerfd, &howmany, sizeof howmany);
std::cout << "TimerQueue::handleRead() " << howmany << " at " << now.toString() << std::endl;
if (n != sizeof howmany)
{
std::cout << "TimerQueue::handleRead() reads " << n << " bytes instead of 8" << std::endl;
}
} void resetTimerfd(int timerfd, TimeStamp expiration)
{
// wake up loop by timerfd_settime()
struct itimerspec newValue;
struct itimerspec oldValue;
bzero(&newValue, sizeof newValue);
bzero(&oldValue, sizeof oldValue);
newValue.it_value = howMuchTimeFromNow(expiration);
int ret = ::timerfd_settime(timerfd, 0, &newValue, &oldValue);
if (ret)
{
std::cout << "timerfd_settime()" << std::endl;
}
}

TimerQueue的结构.

TimerQueue只提供了两个对外的接口

addTimer() 添加一个定时器超时执行回调函数cb. interval是周期性定时时间,本章不讲,置零不打开.

cancel() 取消一个定时器,本章也不细述,本章只介绍addTimer()接口.后面如果需要会补充本章.

TimerQueue定义如下

class TimerQueue
{
public:
TimerQueue(EventLoop* loop);
~TimerQueue(); // Schedules the callback to be run at given time, TimerId addTimer(const NetCallBacks::TimerCallBack& cb, TimeStamp when, double interval = 0.0); void cancel(TimerId timerId); private:
/*
.....
*/
EventLoop* p_loop;
const int m_timerfd;
Channel m_timerfdChannel; //Timer List sorted by expiration
TimerList m_timers;
ActiveTimerSet m_activeTimers;
};

虽然只提供了两个对外接口,但是私有成比较复杂,首先简介成员Timer.

Timer

Timer类作为TimerQueue的内部成员使用,封装一个定时器,addTimer()接口调用后生成一个Timer(),外头的回调函数和定时反应时间会封装再此Timer中.

Tiemr主要接口都是获取这些构造时配置的成员值

run() 调用回调函数.

expiration 定时器过期时间.

interval 周期性定时时间.

repeat 是否是周期性定时.

sequence 一个静态成员,用于记录Timer创建的个数. 为了保证它的线程安全性,使用AtomicInt64封装了一层原子操作.

TimerId 用于Cancel Timer的标志Id, 这两个类都不复杂,可自行参看muduo源码,也可翻我github上的SimpleMuduo单独类文件夹下的测试代码.

  Timer(const NetCallBacks::TimerCallBack& cb, TimeStamp when, double interval)
:m_callBack(cb),
m_expiration(when),
m_interval(interval),
m_repeat(interval > 0.0),
m_sequence(s_numCreated.incrementAndGet())
TimerId TimerQueue::addTimer(const NetCallBacks::TimerCallBack& cb, TimeStamp when, double interval)
{
Timer* timer = new Timer(cb, when, interval);
//p_loop->runInLoop(std::bind(&TimerQueue::addTimerInLoop, this, timer));
return TimerId(timer, timer->sequence());
}

Timer的容器.

  typedef std::pair<TimeStamp, Timer*> Entry;
typedef std::set<Entry> TimerList;
typedef std::pair<Timer*, int64_t> ActiveTimer;
typedef std::set<ActiveTimer> ActiveTimerSet;

为了解决无法处理两个Timer到期时间相同的情况。使用了pair将时间戳和Timer的地址组成了一对.然后使用Set存储.

ActiveTimer 将Timer和sequence组成一对主要作用来索引迭代的.

TimerQueue私有接口介绍.

  void addTimerInLoop(Timer* timer);
void cancelInLoop(TimerId timerId);
//called when timerfd alarms
void handleRead();
//move out all expired timers and return they.
std::vector<Entry> getExpired(TimeStamp now);
bool insert(Timer* timer);
void reset(const std::vector<Entry>& expired, TimeStamp now);

添加定时器

bool insert(Timer* timer); //插入一个定时器.

EventLoop添加了一个runInLoop接口: 在它的IO线程内执行某个用户

任务回调, 即EventLoop::runInLoop(const Functor& cb), 其中Functor是

std::function<void()>。 如果用户在当前IO线程调用这个函数, 回调会

同步进行; 如果用户在其他线程调用runInLoop(), cb会被加入队列, IO

线程会被唤醒来调用这个Functor。

addTimer()使用了EventLoop的runInLoop接口(这个接口主要来保证线程安全性的,暂不讲),来执行addTimerInLoop().addTimerInLoop()调用insert()插入定时器.

如果此定时器是最早触发的那一个则会调用resetTimerfd()->timerfd_settime()启动定时器.

addTimer()->addTimerInLoop()->insert()->resetTimerfd()->timerfd_settime()

更新定时器

添加逻辑就在上面了,下面给出处理逻辑.

三个接口.

void handleRead(); //定时器触发回调.获取已过期的事件并处理随后更新列表.

std::vector getExpired(TimeStamp now);//获取一组已过期的定时器,并从TimerList中删除.

void reset(const std::vector& expired, TimeStamp now);//如果是周期性任务则重新配置时间插入,随后调用resetTimerfd()更新下一定时任务.

handleRead()->getExpired()->Timer->run(cb)->reset()->resetTimerfd()->timerfd_settime()

时序图

muduo网络库学习笔记(三)TimerQueue定时器队列

TimerQueue源码

#ifndef _NET_TIMERQUEUE_HH
#define _NET_TIMERQUEUE_HH
#include "TimerId.hh"
#include "CallBacks.hh"
#include "TimeStamp.hh"
#include "Channel.hh"
#include <set>
#include <vector> class EventLoop; class TimerQueue
{
public:
TimerQueue(EventLoop* loop);
~TimerQueue(); // Schedules the callback to be run at given time, TimerId addTimer(const NetCallBacks::TimerCallBack& cb, TimeStamp when, double interval = 0.0); void cancel(TimerId timerId); private:
typedef std::pair<TimeStamp, Timer*> Entry;
typedef std::set<Entry> TimerList;
typedef std::pair<Timer*, int64_t> ActiveTimer;
typedef std::set<ActiveTimer> ActiveTimerSet; void addTimerInLoop(Timer* timer);
void cancelInLoop(TimerId timerId);
//called when timerfd alarms
void handleRead();
//move out all expired timers and return they.
std::vector<Entry> getExpired(TimeStamp now);
bool insert(Timer* timer);
void reset(const std::vector<Entry>& expired, TimeStamp now); EventLoop* p_loop;
const int m_timerfd;
Channel m_timerfdChannel; //Timer List sorted by expiration
TimerList m_timers;
ActiveTimerSet m_activeTimers; bool m_callingExpiredTimers; /*atomic*/
ActiveTimerSet m_cancelingTimers; }; #endif //TimerQueeu.cpp #include <stdint.h>
#include <assert.h>
#include <sys/timerfd.h>
#include <unistd.h> #include "Logger.hh"
#include "EventLoop.hh"
#include "Timer.hh"
#include "TimerQueue.hh" namespace TimerFd
{ int createTimerfd()
{
int timerfd = ::timerfd_create(CLOCK_MONOTONIC,
TFD_NONBLOCK | TFD_CLOEXEC);
if (timerfd < 0)
{
LOG_SYSFATAL << "Failed in timerfd_create";
}
return timerfd;
} struct timespec howMuchTimeFromNow(TimeStamp when)
{
int64_t microseconds = when.microSecondsSinceEpoch()
- TimeStamp::now().microSecondsSinceEpoch();
if (microseconds < 100)
{
microseconds = 100;
}
struct timespec ts;
ts.tv_sec = static_cast<time_t>(
microseconds / TimeStamp::kMicroSecondsPerSecond);
ts.tv_nsec = static_cast<long>(
(microseconds % TimeStamp::kMicroSecondsPerSecond) * 1000);
return ts;
} void readTimerfd(int timerfd, TimeStamp now)
{
uint64_t howmany;
ssize_t n = ::read(timerfd, &howmany, sizeof howmany);
LOG_TRACE << "TimerQueue::handleRead() " << howmany << " at " << now.toString();
if (n != sizeof howmany)
{
LOG_ERROR << "TimerQueue::handleRead() reads " << n << " bytes instead of 8";
}
} void resetTimerfd(int timerfd, TimeStamp expiration)
{
// wake up loop by timerfd_settime()
LOG_TRACE << "resetTimerfd()";
struct itimerspec newValue;
struct itimerspec oldValue;
bzero(&newValue, sizeof newValue);
bzero(&oldValue, sizeof oldValue);
newValue.it_value = howMuchTimeFromNow(expiration);
int ret = ::timerfd_settime(timerfd, 0, &newValue, &oldValue);
if (ret)
{
LOG_SYSERR << "timerfd_settime()";
}
} }; using namespace TimerFd; TimerQueue::TimerQueue(EventLoop* loop)
:p_loop(loop),
m_timerfd(createTimerfd()),
m_timerfdChannel(p_loop, m_timerfd),
m_timers(),
m_callingExpiredTimers(false)
{
m_timerfdChannel.setReadCallBack(std::bind(&TimerQueue::handleRead, this));
m_timerfdChannel.enableReading();
} TimerQueue::~TimerQueue()
{
m_timerfdChannel.disableAll();
m_timerfdChannel.remove();
::close(m_timerfd);
for (TimerList::iterator it = m_timers.begin();
it != m_timers.end(); ++it)
{
delete it->second;
}
} std::vector<TimerQueue::Entry> TimerQueue::getExpired(TimeStamp now)
{
std::vector<Entry> expired;
Entry sentry = std::make_pair(now, reinterpret_cast<Timer*>UINTPTR_MAX);
TimerList::iterator it = m_timers.lower_bound(sentry);
assert(it == m_timers.end() || now < it->first);
std::copy(m_timers.begin(), it, back_inserter(expired));
m_timers.erase(m_timers.begin(), it); for(std::vector<Entry>::iterator it = expired.begin();
it != expired.end(); ++it)
{
ActiveTimer timer(it->second, it->second->sequence());
size_t n = m_activeTimers.erase(timer);
assert(n == 1); (void)n;
} assert(m_timers.size() == m_activeTimers.size()); return expired;
} TimerId TimerQueue::addTimer(const NetCallBacks::TimerCallBack& cb, TimeStamp when, double interval)
{
Timer* timer = new Timer(cb, when, interval);
p_loop->runInLoop(std::bind(&TimerQueue::addTimerInLoop, this, timer));
return TimerId(timer, timer->sequence());
} void TimerQueue::addTimerInLoop(Timer* timer)
{
p_loop->assertInLoopThread();
bool earliestChanged = insert(timer); if (earliestChanged)
{
resetTimerfd(m_timerfd, timer->expiration());
}
} void TimerQueue::cancel(TimerId timerId)
{
p_loop->runInLoop(std::bind(&TimerQueue::cancelInLoop, this, timerId));
} void TimerQueue::cancelInLoop(TimerId timerId)
{
p_loop->assertInLoopThread();
assert(m_timers.size() == m_activeTimers.size());
ActiveTimer timer(timerId.m_timer, timerId.m_sequence);
ActiveTimerSet::iterator it = m_activeTimers.find(timer);
if(it != m_activeTimers.end())
{
size_t n = m_timers.erase(Entry(it->first->expiration(), it->first));
assert(n == 1);
delete it->first;
}
else if (m_callingExpiredTimers)
{
m_cancelingTimers.insert(timer);
}
assert(m_timers.size() == m_activeTimers.size());
} bool TimerQueue::insert(Timer* timer)
{
p_loop->assertInLoopThread();
assert(m_timers.size() == m_activeTimers.size());
bool earliestChanged = false;
TimeStamp when = timer->expiration();
TimerList::iterator it = m_timers.begin();
if (it == m_timers.end() || when < it->first)
{
earliestChanged = true;
}
{
std::pair<TimerList::iterator, bool> result
= m_timers.insert(Entry(when, timer));
assert(result.second); (void)result;
}
{
std::pair<ActiveTimerSet::iterator, bool> result
= m_activeTimers.insert(ActiveTimer(timer, timer->sequence()));
assert(result.second); (void)result;
} LOG_TRACE << "TimerQueue::insert() " << "m_timers.size() : "
<< m_timers.size() << " m_activeTimers.size() : " << m_activeTimers.size(); assert(m_timers.size() == m_activeTimers.size());
return earliestChanged;
} void TimerQueue::handleRead()
{
p_loop->assertInLoopThread();
TimeStamp now(TimeStamp::now());
readTimerfd(m_timerfd, now); std::vector<Entry> expired = getExpired(now); LOG_TRACE << "Expired Timer size " << expired.size() << " "; m_callingExpiredTimers = true;
m_cancelingTimers.clear(); for(std::vector<Entry>::iterator it = expired.begin();
it != expired.end(); ++it )
{
it->second->run();
} m_callingExpiredTimers = false; reset(expired, now);
} void TimerQueue::reset(const std::vector<Entry>& expired, TimeStamp now)
{
TimeStamp nextExpire; for(std::vector<Entry>::const_iterator it = expired.begin();
it != expired.end(); ++it)
{
ActiveTimer timer(it->second, it->second->sequence());
if(it->second->repeat()
&& m_cancelingTimers.find(timer) == m_cancelingTimers.end())
{//如果是周期定时器则重新设定时间插入. 否则delete.
it->second->restart(now);
insert(it->second);
}
else
{// FIXME move to a free list no delete please
delete it->second;
}
} if (!m_timers.empty())
{
nextExpire = m_timers.begin()->second->expiration();
} if (nextExpire.valid())
{
resetTimerfd(m_timerfd, nextExpire);
}
}

TimerQueue使用示例

测试TimerQueue的addTimer接口.

#include <errno.h>
#include <thread>
#include <strings.h>
#include <poll.h>
#include <functional>
#include "EventLoop.hh"
#include "Channel.hh"
#include "Poller.hh"
#include "Logger.hh"
#include "Timer.hh"
#include "TimeStamp.hh"
#include "TimerQueue.hh" EventLoop* g_loop; void print() { LOG_DEBUG << "test print()"; } void test()
{ LOG_DEBUG << "[test] : test timerQue"; } int main()
{
EventLoop loop;
g_loop = &loop; TimerQueue timerQue(&loop);
timerQue.addTimer(test, times::addTime(TimeStamp::now(), 3.0));
timerQue.addTimer(test, times::addTime(TimeStamp::now(), 3.0));
timerQue.addTimer(test, times::addTime(TimeStamp::now(), 5.0)); loop.loop(); return 0;
}
./test.out
2018-11-11 15:49:22.493990 [TRACE] [Poller.cpp:64] [updateChannel] fd= 3 events3
2018-11-11 15:49:22.494042 [TRACE] [EventLoop.cpp:34] [EventLoop] EventLoop Create 0x7FFFBD3C39B0 in thread 3262
2018-11-11 15:49:22.494047 [TRACE] [Poller.cpp:64] [updateChannel] fd= 5 events3
2018-11-11 15:49:22.494055 [TRACE] [TimerQueue.cpp:172] [insert] TimerQueue::insert() m_timers.size() : 1 m_activeTimers.size() : 1
2018-11-11 15:49:22.494058 [TRACE] [TimerQueue.cpp:55] [resetTimerfd] resetTimerfd()
2018-11-11 15:49:22.494066 [TRACE] [TimerQueue.cpp:172] [insert] TimerQueue::insert() m_timers.size() : 2 m_activeTimers.size() : 2
2018-11-11 15:49:22.494070 [TRACE] [TimerQueue.cpp:172] [insert] TimerQueue::insert() m_timers.size() : 3 m_activeTimers.size() : 3
2018-11-11 15:49:22.494073 [TRACE] [EventLoop.cpp:59] [loop] EventLoop 0x7FFFBD3C39B0 start loopig
2018-11-11 15:49:22.494075 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:23.495462 [TRACE] [Poller.cpp:28] [poll] nothing happended
2018-11-11 15:49:23.495488 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:24.496618 [TRACE] [Poller.cpp:28] [poll] nothing happended
2018-11-11 15:49:24.496640 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:25.494222 [TRACE] [Poller.cpp:24] [poll] 1 events happended
2018-11-11 15:49:25.494253 [TRACE] [TimerQueue.cpp:45] [readTimerfd] TimerQueue::handleRead() 1 at 1541922565.494251
2018-11-11 15:49:25.494316 [TRACE] [TimerQueue.cpp:188] [handleRead] Expired Timer size 2 2018-11-11 15:49:25.494320 [DEBUG] [main.cpp:50] [test] [test] : test timerQue
2018-11-11 15:49:25.494322 [DEBUG] [main.cpp:50] [test] [test] : test timerQue 2018-11-11 15:49:25.494325 [TRACE] [TimerQueue.cpp:55] [resetTimerfd] resetTimerfd()
2018-11-11 15:49:25.494332 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:26.496293 [TRACE] [Poller.cpp:28] [poll] nothing happended
2018-11-11 15:49:26.496318 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:27.494291 [TRACE] [Poller.cpp:24] [poll] 1 events happended
2018-11-11 15:49:27.494319 [TRACE] [TimerQueue.cpp:45] [readTimerfd] TimerQueue::handleRead() 1 at 1541922567.494317
2018-11-11 15:49:27.494328 [TRACE] [TimerQueue.cpp:188] [handleRead] Expired Timer size 1 2018-11-11 15:49:27.494331 [DEBUG] [main.cpp:50] [test] [test] : test timerQue 2018-11-11 15:49:27.494334 [TRACE] [Poller.cpp:20] [poll] Poller::poll()
2018-11-11 15:49:28.495665 [TRACE] [Poller.cpp:28] [poll] nothing happended