Python 如何让长时间的任务；“可取消”；通过Tornado HTTP服务器上的HTTP？

我已经实现了某种繁重任务的HTTP包装器，我选择Tornado作为前端服务器框架（因为繁重的任务是用Python编写的，我只是习惯于Tornado）

目前，我只是直接从Tornado的过程中调用了繁重的任务。我使用jQuery编写了某种基于Web的界面，让它使用表单中设置的参数处理AJAX请求

正如您所想象的，我从web浏览器中抛出的任务是不可取消的。我可以取消的唯一方法是向Python进程发送9或15信号，而用户通常不能这样做

---

我想通过HTTP请求某种类型的“取消”请求来取消当前正在工作的任务。怎样才能做到呢？大多数处理繁重任务的web服务（例如YouTube上的视频编码）都在做什么？

实际上Tornado的

期货

不支持取消（）。此外，即使使用，时间路由作业仍在运行，只需等待结果

唯一的方法，如中所述，是以可以取消的方式实现逻辑（使用一些标志或任何东西）

例如：

• 作业是一个简单的异步睡眠

• /

  列出作业

• /add/TIME

  添加新作业-时间（秒）-指定睡眠时间

• /cancel/ID

  取消作业

代码可能如下所示：

from tornado.ioloop import IOLoop
from tornado import gen, web
from time import time

class Job():

    def __init__(self, run_sec):
        self.run_sec = int(run_sec)
        self.start_time = None
        self.end_time = None
        self._cancelled = False

    @gen.coroutine
    def run(self):
        """ Some job

        The job is simple: sleep for a given number of seconds.
        It could be implemented as:
             yield gen.sleep(self.run_sec)
        but this way makes it not cancellable, so
        it is divided: run 1s sleep, run_sec times 
        """
        self.start_time = time()
        deadline = self.start_time + self.run_sec
        while not self._cancelled:
            yield gen.sleep(1)
            if time() >= deadline:
                break
        self.end_time = time()

    def cancel(self):
    """ Cancels job

    Returns None on success,
    raises Exception on error:
      if job is already cancelled or done
    """
        if self._cancelled:
            raise Exception('Job is already cancelled')
        if self.end_time is not None:
            raise Exception('Job is already done')
        self._cancelled = True

    def get_state(self):
        if self._cancelled:
            if self.end_time is None:
                # job might be running still
                # and will be stopped on the next while check
                return 'CANCELING...'
            else:
                return 'CANCELLED'
        elif self.end_time is None:
            return 'RUNNING...'
        elif self.start_time is None:
            # actually this never will shown
            # as after creation, job is immediately started
            return 'NOT STARTED'
        else:
            return 'DONE'


class MainHandler(web.RequestHandler):

    def get(self, op=None, param=None):
        if op == 'add':
            # add new job
            new_job = Job(run_sec=param)
            self.application.jobs.append(new_job)
            new_job.run()
            self.write('Job added')
        elif op == 'cancel':
            # cancel job - stop running
            self.application.jobs[int(param)].cancel()
            self.write('Job cancelled')
        else:
            # list jobs
            self.write('<pre>') # this is so ugly... ;P
            self.write('ID\tRUNSEC\tSTART_TIME\tSTATE\tEND_TIME\n')
            for idx, job in enumerate(self.application.jobs):
                self.write('%s\t%s\t%s\t%s\t%s\n' % (
                    idx, job.run_sec, job.start_time,
                    job.get_state(), job.end_time
                ))


class MyApplication(web.Application):

    def __init__(self):

        # to store tasks
        self.jobs = []

        super(MyApplication, self).__init__([
            (r"/", MainHandler),
            (r"/(add)/(\d*)", MainHandler),
            (r"/(cancel)/(\d*)", MainHandler),
        ])

if __name__ == "__main__":
    MyApplication().listen(8888)
    IOLoop.current().start()

然后取消一些。。。注意-它只需要龙卷风

这个例子很简单，

gen.sleep

是你的繁重任务。当然，并不是所有的工作都像以可取消的方式实现的那样简单

for a in `seq 12 120`; do curl http://127.0.0.1:8888/add/$a; done