Tornado Handler Thread Decorator

tornado_handler_thread_decorator.py

from concurrent.futures import ThreadPoolExecutor
from datetime import timedelta
from tornado import gen
from tornado.concurrent import run_on_executor

THREADPOOL_MAX_WORKERS = 10
THREADPOOL_TIMEOUT_SECS = 30


def onthread(function):
    @gen.coroutine
    def decorated(self, *args, **kwargs):
        future = executed(self, *args, **kwargs)
        try:
            response = yield gen.with_timeout(
                timedelta(seconds=THREADPOOL_TIMEOUT_SECS), future)
            if isinstance(response, types.GeneratorType):  # subthreads
                response = yield gen.with_timeout(
                    timedelta(seconds=settings.THREADPOOL_TIMEOUT_SECS),
                    next(response))
        except gen.TimeoutError as exc:
            future.cancel()
            raise exc
        self.write(response)

    @run_on_executor
    def executed(*args, **kwargs):
        return function(*args, **kwargs)

    return decorated
  
# Usage
class BaseHandler(object):
    executor = ThreadPoolExecutor(max_workers=THREADPOOL_MAX_WORKERS)
    ...

class MyHandler(BaseHandler):

    @onthread
    def get(self):
        ...
        return response

class MyOtherHandler(BaseHandler):

    @onthread
    def get(self):
        yield self.couroutine()

    @gen.coroutine
    def couroutine():
        data = yield {
            'one': self.threaded_one(),
            'two': self.threaded_two(),
        }
        return data

    @run_on_executor
    def threaded_one():
        ...
        return response

    @run_on_executor
    def threaded_two():
        ...
        return response

Hi ! I really wanted to thank you for this decorator, you saved me a lot of headaches !

I'm working on a opensource scraper webapp based on Tornado and Scrapy, and launching spiders as background tasks was really a painpoint untill I tried to implement your solution.
You can see your decorator added here, and the repo is there

This opensource scraper project is really in its early stage and it's my first experience with Tornado, so you would certainly see many weird stuff in my code... but at least I know your part works great !!!