Example Tornado server with multiple processes running background tasks

tornado_multiproc.py

import time

form tornado import (
  concurrent,
  gen,
  httpserver,
  ioloop,
  log,
  process,
  web
)


log.enable_pretty_logging()

# thread pool for async background tasks
executor = concurrent.futures.ThreadPoolExecutor(8)


class MainHandler(web.RequestHandler):
  
  def get(self):
    def task(t):
      time.sleep(t)
      print("\nCallback complete\n")
    executor.submit(task, 10)
    self.write(f"Request accepted on process {process.task_id()}\n")
    
    
@gen.coroutine
def small_loop():
  while True:
    yield print('in small loop!\n')
    yield gen.sleep(10)
    
    
def make_app():
  return web.Application([
    (r"/", MainHandler)
  ],
    debug=False)


def main():
  app = make_app()
  
  # start server
  server = httpserver.HTTPServer(app)
  server.bind(8080)
  server.start(0)   # Processes = number of CPUs
  
  # assign background task
  if process.task_id() == 0:
    ioloop.IOLoop.instance().spawn_callback(small_looop)
    
  # assign periodic task
  if process.task_id() == 1:
    task = ioloop.PeriodicCallback(
            lambda: print('period'),
            2000)   # 2000 ms
    task.start()
  
  print('starting ioloop')
  ioloop.IOLoop.current().start()
  
  
if __name__ == "__main__":
  main()