我正在使用我从这个网站获得的阻塞队列示例,认为它非常好。 此阻塞队列使用boost :: mutex。 有时抛出异常:
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::system::system_error> >'
what():错误的文件描述符
以下是阻止队列代码:
#include <boost/thread/mutex.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/condition_variable.hpp>
#include <exception>
#include <list>
#include <stdio.h>
struct BlockingQueueTerminate
: std::exception
{};
namespace tools {
template<class T>
class BlockingQueue
{
private:
boost::mutex mtx_;
boost::condition_variable cnd_;
std::list<T> q_;
unsigned blocked_;
bool stop_;
public:
BlockingQueue()
: blocked_()
, stop_()
{}
~BlockingQueue()
{
this->stop(true);
}
void stop(bool wait)
{
// tell threads blocked on BlockingQueue::pull() to leave
boost::mutex::scoped_lock lock(mtx_);
stop_ = true;
cnd_.notify_all();
if(wait) // wait till all threads blocked on the queue leave BlockingQueue::pull()
while(blocked_)
cnd_.wait(lock);
}
void put(T t)
{
boost::mutex::scoped_lock lock(mtx_); // The exception is thrown here !
q_.push_back(t);
cnd_.notify_one();
}
T pull()
{
boost::mutex::scoped_lock lock(mtx_);
++blocked_;
while(!stop_ && q_.empty())
cnd_.wait(lock);
--blocked_;
if(stop_) {
cnd_.notify_all(); // tell stop() this thread has left
throw BlockingQueueTerminate();
}
T front = q_.front();
q_.pop_front();
return front;
}
};
}
任何人都可以发现这里出了什么问题?因为我整天都试着弄清楚这一点。我想我需要外眼看到它。 寻找评论'//抛出异常!'看看问题究竟发生在哪里。
编辑1:
上下文:我正在使用此阻塞队列来创建MySQL异步包装器。
这是我的MySQL.hh
#ifndef MYSQL_HH_
# define MYSQL_HH_
# include <boost/asio.hpp>
# include <boost/thread.hpp>
# include <boost/function.hpp>
# include <mysql++/mysql++.h>
# include <queue>
# include "async_executor.hh"
# include "BlockingQueue.hh"
class t_mysql_event {
public:
t_mysql_event(std::string query, boost::function<void(mysqlpp::StoreQueryResult)> cb) :
m_query(query), m_store_cb(cb), m_store_bool(true) {}
t_mysql_event(std::string query, boost::function<void()> cb) :
m_query(query), m_exec_cb(cb), m_store_bool(false) {}
bool is_store_query() {
return m_store_bool;
}
std::string toString() {
return m_query;
}
std::string m_query;
boost::function<void(mysqlpp::StoreQueryResult)> m_store_cb;
boost::function<void()> m_exec_cb;
private:
bool m_store_bool;
};
namespace pools {
class MySQL {
public:
~MySQL() {}
static MySQL* create_instance(boost::asio::io_service& io);
static MySQL* get_instance();
void exec(std::string query, boost::function<void()> cb);
void store(std::string query, boost::function<void(mysqlpp::StoreQueryResult)> cb);
private:
MySQL(boost::asio::io_service& io) : executor(io, 100), parent_io(io), m_strand(io)
{
for (int i=0; i < 100; ++i) {
boost::thread(boost::bind(&MySQL::retreive, this));
}
}
void async_exec(std::string query, boost::function<void()> cb, mysqlpp::Connection& conn);
void async_store(std::string query, boost::function<void(mysqlpp::StoreQueryResult)> cb, mysqlpp::Connection& conn);
void retreive();
private:
tools::async_executor executor;
boost::asio::io_service& parent_io;
boost::asio::strand m_strand;
tools::BlockingQueue<t_mysql_event*> m_events;
std::queue<mysqlpp::Connection*> m_stack;
};
}
#endif //MYSQL_HH_
这是MySQL.cc:
#include "MySQL.hh"
static pools::MySQL* _instance = 0;
namespace pools {
MySQL* MySQL::create_instance(boost::asio::io_service& io) {
if (!_instance)
_instance = new MySQL(io);
return _instance;
}
MySQL* MySQL::get_instance() {
if (!_instance) {
exit(1);
}
return _instance;
}
void MySQL::exec(std::string query, boost::function<void()> cb) {
m_events.put(new t_mysql_event(query, cb));
}
void MySQL::store(std::string query, boost::function<void(mysqlpp::StoreQueryResult)> cb) {
m_events.put(new t_mysql_event(query, cb));
}
void MySQL::retreive() {
mysqlpp::Connection conn("***", "***", "***", "***");
for(;;) {
t_mysql_event *event = m_events.pull();
if (event->is_store_query())
async_store(event->m_query, event->m_store_cb, conn);
else
async_exec(event->m_query, event->m_exec_cb, conn);
delete event;
}
}
void MySQL::async_exec(std::string query, boost::function<void()> cb, mysqlpp::Connection& conn) {
mysqlpp::Query db_q = conn.query(query.c_str());
db_q.exec();
parent_io.post(cb);
}
void MySQL::async_store(std::string query, boost::function<void(mysqlpp::StoreQueryResult)> cb, mysqlpp::Connection& conn) {
mysqlpp::Query db_q = conn.query(query.c_str());
mysqlpp::StoreQueryResult res = db_q.store();
parent_io.post(boost::bind(cb, res));
}
}
之后:
class MyClass {
public:
MyClass() : _mysql(pools::MySQL::get_instance()) {}
startQueries();
private:
void Query1() {
std::stringstream query("");
query << "INSERT INTO Table1 ***";
_mysql->exec(query.str(),
boost::bind(&MyClass::Query2, this, _1));
}
void Query2() {
std::stringstream query("");
query << "INSERT INTO Table2 ***";
_mysql->exec(query.str(),
boost::bind(&MyClass::Query3, this, _1));
}
void Query3() {
std::stringstream query("");
query << "INSERT INTO Table3 ***";
_mysql->exec(query.str(),
boost::bind(&MyClass::done, this, _1));
}
void done() {}
pools::MySQL *_mysql;
};
希望能回答一些更多信息的请求......
有趣的事情:
如果我用pool :: MySQL :: get_instance()替换每个_mysql,我似乎没有崩溃。 但我怀疑在下面有一个更重要的错误......
答案 0 :(得分:0)
如果队列已被销毁但您尝试调用其put
方法,则可以抛出此异常。通过在队列析构函数中放置断点(或print语句)来检查这一点。