我已经实现了某种繁重任务的HTTP包装器,我选择了Tornado作为前端服务器框架(这是因为繁重的任务是用Python编写的,而我只是习惯于Tornado)。
目前,我只是从龙卷风的过程中直接调用繁重的任务。我使用jQuery准备了某种基于Web的界面,让它以表单中设置的参数进行AJAX请求。
如您所料,我从网络浏览器中抛出的任务无法取消。我可以取消的唯一方法是向Python进程发送9或15个信号,而这通常不是用户可以做的。
我想通过HTTP请求某种“取消”请求来取消当前正在工作的任务。怎么做到呢?大多数处理繁重任务(例如YouTube中的视频编码)的网络服务在做什么?
实际上,龙卷风Futures
不支持取消(docs)。而且,即使使用with_timeout
,超时的作业仍在运行,没有什么等待其结果。
唯一的方法,如我如何在超时的情况下如何取消龙卷风中悬挂的异步任务中所述?,是用可以取消的逻辑(带有一些标志或其他任何东西)来实现。
例子:
/
列出工作/add/TIME
添加新工作-时间以秒为单位-指定睡眠时间/cancel/ID
取消工作该代码可能类似于:
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()
添加情侣职位:
for a in `seq 12 120`; do curl http://127.0.0.1:8888/add/$a; done
然后取消一些...注意-仅需要龙卷风。
这个例子很简单,gen.sleep
这将是您繁重的工作。当然,并非所有工作都像以可取消的方式实施那样简单。
本文收集自互联网,转载请注明来源。
如有侵权,请联系[email protected] 删除。
我来说两句