pthread没有为类实例启动 [英] pthread is not starting for class instance
问题描述
注意:C ++ 98
您好,我对c ++有点陌生,我正在编写一个databaes程序,并尝试使用pthread的boost :: asio包启动计时器.计时器的目的是在将sql查询放入缓冲区后启动,如果一段时间未接收到任何内容,缓冲区将运行execute函数.我设法将其编译,但看起来pthread实例似乎没有启动.
Hi, I'm a little new to c++ and I am writing a databaes program and am attempting to start a timer using the boost::asio package using pthread. The aim of the timer is to start after sql queries have been placed inside a buffer, of which will run an execute function if nothing has been received for a period of time. I have managed to get it to compile, but it doesn't look like the pthread instance is starting.
我已经在我的getInstance方法中调用了pthread,并且相应地设置了boost :: asio警报.我将在下面显示的是,通过直接调用io_run()
来启动计时器,该计时器会在警报内陷入循环.
I have called the pthread inside my getInstance method, and the boost::asio alarm has been set up accordingly. What I will show below is that by calling io_run()
directly starts the timer falls into a loop within the alarm.
数据库.h
void *run_io(void *arg);
class Database
{
private:
static Database *dbInstance; //= NULL;
public:
boost::asio::io_service io_service;
boost::posix_time::millisec interval;
boost::asio::deadline_timer timer;
pthread_t timerThread;
public:
static Database &getInstance()
{
if (!dbInstance)
{
dbInstance = new Database();
// pthread_create(&dbInstance->timerThread,NULL,run_io,&dbInstance->io_service);
std::cout << " INSTANCE CREATED " << std::endl;
pthread_create(&dbInstance->timerThread, NULL, run_io, (void *)&dbInstance->io_service);
// pthread_join(&dbInstance->timerThread, NULL);
}
return *dbInstance;
}
};
database.cpp
Database *Database::dbInstance = NULL;
Database::Database()
: interval(2000), timer(io_service, interval) {}
Database::~Database()
{
sqlite3_close(db);
}
void Database::setAlarm(const boost::system::error_code& /* e */)
{
std::cout << "[TEST] WE ARE IN SET ALARM " << std::endl;
DB_WRITE_TIME = 500;
boost::posix_time::milliseconds interval(DB_WRITE_TIME);
// Reschedule the timer for 1 second in the future:
timer.expires_at(timer.expires_at() + interval);
// Posts the timer event
timer.async_wait(boost::bind(&Database::setAlarm, this, _1));
}
int Database::buffer()
{
// DO BUFFER STUFF
timer.async_wait(boost::bind(&Database::setAlarm, this, _1));
// io_service.run() <-- uncommenting this results in the loop
return rc ;
}
void *run_io(void *arg)
{
boost::asio::io_service *io_service = (boost::asio::io_service *)arg;
io_service->run();
}
所以我觉得pthread甚至还没有启动.我尝试在其中放一个打印语句,看看它是否出来了,但终端中什么也没出现.
So I don't feel like the pthread is even starting. I tried putting a print statement in there to see if it came out, and nothing appeared in my terminal.
我已经按照Sehe的建议进行了更改,但是看起来仍然无法调用警报处理程序(setAlarm()
).我必须对其稍作修改以使其与整个程序兼容,但实际上就是这样(我给间隔时间指定了5000的值,以使其有足够的时间进行测试):
I have made changes as per Sehe's advice, however it still does not look like I am able to call the alarm handler (setAlarm()
). I had to slightly modify it to be compatible with the whole program, but essentially it is this (I gave the interval time a value of 5000 to give it enough time for the tests):
数据库.h
class Database
{
private:
static boost::shared_ptr<Database> dbInstance;
private:
typedef boost::asio::io_service io_service;
io_service io;
boost::scoped_ptr<io_service::work> work;
boost::posix_time::millisec interval;
boost::asio::deadline_timer timer;
boost::thread timerThread;
void run_io()
{
std::cout << "ENTER IO THREAD" << std::endl;
io.run();
std::cout << "LEAVE IO THREAD" << std::endl;
}
public:
static Database &getInstance()
{
if (!dbInstance)
{
std::cout << " INSTANCE CREATED " << std::endl;
dbInstance.reset(new Database());
dbInstance->timerThread = boost::thread(boost::bind(&Database::run_io,dbInstance));
}
return *dbInstance;
}
Database(); // <-- default constructor (doesn't take any args)
~Database();
database.cpp
boost::shared_ptr<Database> Database::dbInstance;
static const int DB_WRITE_TIME = 5000;
Database::Database()
: work(new io_service::work(io)), interval(5000), timer(io, interval)
{
// std::cout << " CONSTRUCTED " << std::endl;
}
Database::~Database()
{
// std::cout << " DESTROYED " << std::endl;
// sqlite3_close(db);
}
void Database::setAlarm(const boost::system::error_code& ec)
{
std::cout << "[TEST] WE ARE IN SET ALARM - ec message = " << ec.message() << std::endl;
executeSqlInBuffer(); // once timer expire, call the execute function
if(!ec)
{
boost::posix_time::milliseconds interval(DB_WRITE_TIME);
timer.expires_from_now(interval);
timer.async_wait(boost::bind(&Database::setAlarm, this, _1));
}
}
void Database::teardown()
{
// std::cout << " INSTANCE SHUTTING DOWN " << std::endl;
timer.cancel(); // stop timer loop
work.reset(); // allows io.run() to exit
if(timerThread.joinable())
{
std::cout << " JOINED " << std::endl;
timerThread.join(); // releasing bound of shared_ptr
}
else std::cout << " NOT JOINED " << std::endl;
dbInstance.reset(); // releasing instance
}
int Database::buffer()
{
// do buffering
if(buffer.size() == max_size)
{
executeSqlInBuffer();
}
std::cout << timer.expires_from_now(interval) << std::endl;
// std::cout << " ~ BEFORE TIMER ~ " << std::endl;
timer.async_wait(boost::bind(&Database::setAlarm, this, _1));
return 1;
}
main.cpp
int main()
{
pthread_t thread1; // a few pthreads in main that handle other areas of the program.
pthread_create(&thread1,NULL,thread1Arg,NULL);
pthread_t dbThread; // my pthread for the database
pthread_create(&dbThread,NULL,dbThreadArg,NULL);
Database& database = Database::getInstance();
database.teardown();
pthread_join(thread1,NULL);
pthread_join(dbThread,NULL);
return 0;
}
您还可以在此处看到它进入和离开IO线程,并创建一个实例,以及timer.expires_from_now(interval)
的调试输出:
You can also see here that it enters and leaves the IO thread, and creates an instance, plus the debug output for timer.expires_from_now(interval)
:
INSTANCE CREATED
JOINED
ENTER IO THREAD
LEAVE IO THREAD
...
...
0 ---> first cycle
1 ---> second cycle
...
1 ---> nth cycle
推荐答案
我非常困惑为什么使用Boost或C ++ 11(或同时使用两者)的任何人都将使用原始的pthread
线程(请参见例如 C ++ Boost异步计时器可以并行运行与程序配合使用)
I'm very ccnfused why anyone who uses Boost or C++11 (or both...) would ever use raw pthread
threads (see e.g. C++ boost asynchronous timer to run in parallel with program for a good juxtaposition).
真正的问题很可能是您的io_service
用尽了工作(请参见例如
The real problem is likely that you have io_service
running out of work (see e.g. https://www.boost.org/doc/libs/1_57_0/doc/html/boost_asio/reference/io_service__work.html).
如果您没有待处理的异步操作,线程将退出.
If you have no pending async operations the thread just exits.
另一个问题是准确性问题
Another problem is accuracy issues with
timer.expires_at(timer.expires_at() + interval);
某些处理程序可能花费很长时间,以至于您安排下一个警报时,截止日期已经到期.最好使用
It's possible that some handlers take so much time that by the time you schedule your next alarm, the deadline has already expired. It's probably better to use
timer.expires_from_now(interval);
请注意,这也可以更好地匹配注释.该注释已经受注释的困扰,因为它说"1秒",但实际上它是一些已定义的常量
DB_WRITE_TIME
或以其他方式将您的计时器与其他处理程序分开,以确保准确的安排.
or separate your timer from the other handlers in some other way to guarantee accurate scheduling.
最后,由于没有任何关机,您拥有 UB .静态实例永远不会被破坏,但值得的是,从未连接的非分离线程永远不会被连接,从而在关机时会产生未定义的行为.
Finally, you had UB due to the absense of any shutdown. The static instance never gets destroyed, but what's worth the non-detached thread never is joined, creating undefined behaviour at shutdown.
This problem is actually almost identical to the one recently discussed here, where I also explains the way
work
guards work in more detail: asio::io_service is ending immediately with work
下面是对c ++ 11的重写,其中包含必要的修复程序:
由于我现在注意到您由于某种奇怪的原因而陷入了c ++ 03领域,因此使用了Boost Thread版本:
Since I now noticed you're that person stuck in c++03 land for some weird reason, a Boost Thread version:
Live On Coliru
#include <boost/asio.hpp>
#include <boost/make_shared.hpp>
#include <boost/scoped_ptr.hpp>
#include <boost/thread.hpp>
#include <iostream>
static const int DB_WRITE_TIME = 500;
class Database
{
private:
static boost::shared_ptr<Database> dbInstance;
Database()
: work(new io_service::work(io)),
interval(750),
timer(io, interval)
{
std::cout << "INSTANCE CREATED" << std::endl;
}
void on_timer_completed(const boost::system::error_code& ec) {
std::cout << "[on_timer_completed] " << ec.message() << std::endl;
if (!ec) {
boost::posix_time::milliseconds interval(DB_WRITE_TIME);
// Reschedule the timer
timer.expires_from_now(interval);
timer.async_wait(boost::bind(&Database::on_timer_completed, this, _1));
}
}
int buffer()
{
// DO BUFFER STUFF
timer.expires_from_now(interval);
timer.async_wait(boost::bind(&Database::on_timer_completed, this, _1));
// io_service.run() <-- uncommenting this results in the loop
return 1; // rc ;
}
public:
void do_stuff() {
buffer(); // whatever it does
}
void teardown() {
std::cout << "INSTANCE SHUTTING DOWN\n";
timer.cancel(); // stop timer loop
work.reset(); // allows io.run() to exit
if (timerThread.joinable()) {
timerThread.join(); // releasing the bound shared_ptr
}
dbInstance.reset(); // releasing the instance
}
~Database() {
//sqlite3_close(db);
std::cout << "INSTANCE DESTROYED\n";
}
private:
typedef boost::asio::io_service io_service;
io_service io;
boost::scoped_ptr<io_service::work> work;
boost::posix_time::millisec interval;
boost::asio::deadline_timer timer;
boost::thread timerThread;
void run_io() {
std::cout << "ENTER IO THREAD" << std::endl;
io.run();
std::cout << "LEAVE IO THREAD" << std::endl;
}
public:
static Database &getInstance()
{
if (!dbInstance)
{
dbInstance.reset(new Database());
dbInstance->timerThread =
boost::thread(boost::bind(&Database::run_io, dbInstance));
}
return *dbInstance;
}
};
boost::shared_ptr<Database> Database::dbInstance;
int main() {
Database& db = Database::getInstance();
boost::this_thread::sleep_for(boost::chrono::seconds(1));
db.do_stuff();
boost::this_thread::sleep_for(boost::chrono::seconds(3));
// ....
db.teardown();
}
打印
INSTANCE CREATED
ENTER IO THREAD
[on_timer_completed] Success
[on_timer_completed] Success
[on_timer_completed] Success
[on_timer_completed] Success
[on_timer_completed] Success
INSTANCE SHUTTING DOWN
[on_timer_completed] Operation canceled
LEAVE IO THREAD
INSTANCE DESTROYED
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