Flask，boost::python 和线程

Question

我有一个通过 boost::python 公开的 C++ class:

class RunnerState {
public:
    RunnerState(std::string& input) : m_output(3, 0) {  }
    std::vector<int>& get_output() { return m_output; }
    void run() {
        std::unique_lock<std::mutex> running(m);
        t = new std::thread([this] (std::unique_lock<std::mutex> running) {
            sleep(10);
        }, std::move(running));
    }
    bool is_running() {
        if(m.try_lock()) {
            m.unlock();
            return false;
        }
        return true;
    }
private:
    std::thread *t;
    std::mutex m;
};

BOOST_PYTHON_MODULE(librunner)
{
    class_<std::vector<int>>("int_vector").def(vector_indexing_suite<std::vector<int>>());
    class_<RunnerState, boost::noncopyable>("RunnerState", init<std::string>())
        .def("get_output", &RunnerState::get_output, return_value_policy<copy_non_const_reference>())
        .def("run", &RunnerState::run)
        .def("is_running", &RunnerState::run);
}

然后由 Flask 网络服务使用：

from flask import Flask, request
import librunner
app = Flask(__name__)
current_run = None

@app.route('/run', methods=['POST'])
def run():
    data = request.get_data()
    current_run = librunner.Run(data)
    output = current_run.get_output()
    # do something with output...
    current_run.run()
    return "Success!", 200, {'Content-Type': 'text/plain'}

@app.route('/running')
def running():
    result = False
    if current_run != None:
        result = current_run.is_running()
    return str(result), 200, {'Content-Type': 'text/plain'}

问题是 POST 对 /run 的请求不会 return 直到在 C++ 中创建的线程退出。为什么？

我猜测这与 Boost::Python return 价值政策和 Boost::Python 在指定时间内保持 returned 价值有关，但我无法具体指出问题所在。

Answer 1

这里的问题是函数不访问 current_run 全局变量，而是它们各自得到一个名为 current_run 的局部变量。这是通过将 python 更改为以下内容来解决的：

from flask import Flask, request
import librunner
app = Flask(__name__)
current_run = None

@app.route('/run', methods=['POST'])
def run():
    data = request.get_data()
    global current_run
    current_run = librunner.Run(data)
    output = current_run.get_output()
    # do something with output...
    current_run.run()
    return "Success!", 200, {'Content-Type': 'text/plain'}

@app.route('/running')
def running():
    result = False
    global current_run
    if current_run != None:
        result = current_run.is_running()
    return str(result), 200, {'Content-Type': 'text/plain'}

Flask，boost::python 和线程

Flask, boost::python and threads

c++

python

multithreading

boost-python

flask