c++ - 在异步模式下使用 boost 进程运行进程并超时
问题描述
在下面的代码中,我试图实现一个运行 shell 命令并获取stdio
,stderr
并返回代码的程序。我正在按照此处boost process
建议的async
模式使用它。
namespace bp = boost::process;
class Process {
public:
Process(std::string & cmd, const int timeout);
void run();
private:
void timeout_handler();
const std::string command;
const int timeout;
bool killed;
bool stopped;
std::string stdOut;
std::string stdErr;
int returnStatus;
boost::asio::io_service ios;
boost::process::group group;
boost::asio::deadline_timer deadline_timer;
};
Process::Process(std::string & cmd, const int timeout):
command(cmd),
timeout(timeout),
deadline_timer(ios)
{}
void Process::timeout_handler()
{
if (stopped)
return;
if (deadline_timer.expires_at() <= boost::asio::deadline_timer::traits_type::now())
{
std::cout << "Time Up!" << std::endl;
group.terminate();
std::cout << "Killed the process and all its decendents" << std::endl;
killed = true;
stopped = true;
deadline_timer.expires_at(boost::posix_time::pos_infin);
}
deadline_timer.async_wait(std::bind(&Process::timeout_handler, this));
}
void Process::run()
{
std::future<std::string> dataOut;
std::future<std::string> dataErr;
bp::child c(command, bp::std_in.close(), bp::std_out > dataOut, bp::std_err > dataErr, ios, group);
deadline_timer.expires_from_now(boost::posix_time::seconds(timeout));
deadline_timer.async_wait(std::bind(&Process::timeout_handler, this));
ios.run();
c.wait();
stdOut = dataOut.get();
stdErr = dataErr.get();
returnStatus = c.exit_code();
}
int main(int argc, char** argv)
{
if(argc < 2)
{
std::cout << "Usage: \na.out <command>" << std::endl;
exit(1);
}
std::vector<std::string> arguments(argv + 1, argv + argc);
std::string command;
for( const auto & tok : arguments)
{
command += tok + " ";
}
std::cout << command << std::endl;
Process p(command, 10);
p.run();
return 0;
}
现在,上面的代码只有在deadline_timer
过期后才返回。我想要的是,如果子进程在计时器到期之前完成,或者它(连同它派生的所有子进程)应该终止,它应该退出。请指出我代码中的错误。
解决方案
错误确实很简单:你应该取消deadline timer!
io_service::run()
不会返回,除非
- 从处理程序发出的异常
- 没有更多的工作在排队。
当最后期限计时器正在进行时,这意味着不满足第二个条件。所以io_service::run()
等待它,因为你要求它。
其他注意事项:
- 使用错误代码来检测计时器取消而不是激烈的时间比较
- 无需循环链接计时器(事实上,这要求 io_service 永远不会完成的错误)
- 您的代码未能初始化
stopped
和killed
Live On Coliru
#include <boost/process.hpp>
#include <boost/process/async.hpp>
#include <boost/asio.hpp>
#include <boost/bind.hpp>
#include <iostream>
namespace bp = boost::process;
class Process {
public:
Process(std::string &cmd, const int timeout);
void run();
private:
void timeout_handler(boost::system::error_code ec);
const std::string command;
const int timeout;
bool killed = false;
bool stopped = false;
std::string stdOut;
std::string stdErr;
int returnStatus = 0;
boost::asio::io_service ios;
boost::process::group group;
boost::asio::deadline_timer deadline_timer;
};
Process::Process(std::string &cmd, const int timeout) : command(cmd), timeout(timeout), deadline_timer(ios) {}
void Process::timeout_handler(boost::system::error_code ec) {
if (stopped)
return;
if (ec == boost::asio::error::operation_aborted)
return;
if (deadline_timer.expires_at() <= boost::asio::deadline_timer::traits_type::now()) {
std::cout << "Time Up!" << std::endl;
group.terminate(); // NOTE: anticipate errors
std::cout << "Killed the process and all its decendants" << std::endl;
killed = true;
stopped = true;
deadline_timer.expires_at(boost::posix_time::pos_infin);
}
//NOTE: don't make it a loop
//deadline_timer.async_wait(boost::bind(&Process::timeout_handler, this, boost::asio::placeholders::error));
}
void Process::run() {
std::future<std::string> dataOut;
std::future<std::string> dataErr;
deadline_timer.expires_from_now(boost::posix_time::seconds(timeout));
deadline_timer.async_wait(boost::bind(&Process::timeout_handler, this, boost::asio::placeholders::error));
bp::child c(command, bp::std_in.close(), bp::std_out > dataOut, bp::std_err > dataErr, ios, group,
bp::on_exit([=](int e, std::error_code ec) {
// TODO handle errors
std::cout << "on_exit: " << ec.message() << " -> " << e << std::endl;
deadline_timer.cancel();
returnStatus = e;
}));
ios.run();
stdOut = dataOut.get();
stdErr = dataErr.get();
c.wait();
returnStatus = c.exit_code();
}
int main(int argc, char **argv) {
if (argc < 2) {
std::cout << "Usage: \na.out <command>" << std::endl;
exit(1);
}
std::vector<std::string> arguments(argv + 1, argv + argc);
std::string command;
for (const auto &tok : arguments) {
command += tok + " ";
}
std::cout << command << std::endl;
Process p(command, 2);
p.run();
}
打印例如
$ ./sotest 'echo hello'
echo hello
on_exit: Success -> 0
$ ./sotest 'sleep 1'
sleep 1
on_exit: Success -> 0
$ ./sotest 'sleep 3'
sleep 3
Time Up!
Killed the process and all its decendants
on_exit: Success -> 9
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