muduo网络库学习笔记(三)TimerQueue定时器队列
目录
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
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