NOTE: C++98
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.
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.
database.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();
}
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.
---- EDIT ----
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):
database.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;
}
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
