Function definitions are not always updated when redefined.

[robertnishihara]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): MacOS
• Ray installed from (source or binary): source at ccbcc4b
• Python version: 3.6

Run the following in IPython.

import ray

ray.init()

@ray.remote
def f():
    time.sleep(1)

ray.get(f.remote())  # This will raise an exception because 'time' is not defined.

Then in the same interpreter, run

import time

@ray.remote
def f():
    time.sleep(1)

ray.get(f.remote())

It should work the second time, since time has now been imported and f has been redefined. However, instead it fails with the same error as the first time.

RayTaskError(NameError): ray_worker:__main__.f() (pid=27630, ip=192.168.42.11)
  File "python/ray/_raylet.pyx", line 548, in ray._raylet.execute_task
    with core_worker.profile_event(b"task:execute"):
  File "python/ray/_raylet.pyx", line 550, in ray._raylet.execute_task
    outputs = function_executor(*args, **kwargs)
  File "<ipython-input-1-eadbd19a0c80>", line 7, in f
NameError: name 'time' is not defined

Note that if I modify the code in f slightly, e.g., to sleep for 2 seconds instead of 1, then it works.

@edoakes @pcmoritz I assume that we're hashing the function source code instead of the pickled function and that's what's causing the issue. Forgetting import statements happens all the time in interactive development in IPython and you often need to import them and then redefine the function.