CODEWITHSUNDEEP
pythontornado
Vikas Tiwari
Vikas Tiwari

Reputation: 537

Background timer via Tornado IOLoop.spawn_callback

I want to run a timer in a tornado based web app such that the it runs in background and is non blocking.

Once the timer finishes, a specific task has to be called so it is very important that the timer completes exactly on time.

What should be the ideal way to do it ?

I read Tornado IOLoop.spawn_callback in the documentation but I am not very clear that it would behave correctly.

I don't quite understand the statement in the doc

Unlike all other callback-related methods on IOLoop, spawn_callback does not associate the callback with its caller’s stack_context

Upvotes: 0

Views: 743

Answers (1)

xyres
xyres

Reputation: 21834

If you want to run a function after a specific time, you can use IOLoop.call_later. Use it like this:

IOLoop.current().call_later(5, my_func) # will call my_func 5 seconds later

def my_func():
    # do something

IOLoop.spawn_callback is used for running a callback/function in the next iteration of the IOLoop, that is - almost instantly. You can't add a time out to spawn_callback. Since you want to schedule a callback after a timeout, IOLoop.call_later is what you need.

In your comment you asked

Why according to you IOLoop.spawn_callback is not to be used?

Well, I never said to not use it. You can use it if you need it. In this case, you don't.

So, when do you need it? When you'll need to run a callback almost instantly, without a timeout, that's when you can use spawn_callback. But even then, there's IOLoop.add_callback which is used much more widely than spawn_callback.

Upvotes: 2

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