Ray: Actor not printing when launched in jupyter

[zifeo]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Linux Ubuntu 16.04
• Ray installed from (source or binary): pip3 install ray
• Ray version: 0.6.1
• Python version: 3.5.2
• Exact command to reproduce: run following code from inside a Jupyter notebook or from a vanilla python file

Describe the problem

Printing inside actors should show up in the stdout/stdrr or at least in logs when launched from inside a Jupyter notebook. For the moment, nothing is visible.

Source code / logs

import ray
ray.init()

@ray.remote
class Counter(object):
    def __init__(self):
        self.value = 0

    def increment(self):
        self.value += 1
        print(self.value)
        return self.value

c = Counter.remote()
print(ray.get(c.increment.remote()))

Give 1 then 1 when python3 test.py but only 1 inside notebook.

[richardliaw]

Hm. it might be that the stdout of the jupyter notebook belongs to the main
jupyter kernel/process. The output should show up in the console where you
start the Jupyter notebook.

Following this thread: https://github.com/ipython/ipython/issues/8863,
maybe you can try sys.stdout.flush()?

Let me know if that changes anything.

On Fri, Jan 4, 2019 at 2:38 PM Teo Stocco [e-mail] wrote:

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Linux
  Ubuntu 16.04
• Ray installed from (source or binary): pip3 install ray
• Ray version: 0.6.1
• Python version: 3.5.2
• Exact command to reproduce: run following code from inside a
  Jupyter notebook or from a vanilla python file

Describe the problem

Printing inside actors should show up in the stdout/stdrr or at least in
logs when launched from inside a Jupyter notebook. For the moment, nothing
is visible.
Source code / logs

import ray
ray.init()
@ray.remoteclass Counter(object):
def __init__(self):
self.value = 0

def increment(self):
    self.value += 1
    print(self.value)
    return self.value

c = Counter.remote()print(ray.get(c.increment.remote()))

Give 1 then 1 when python3 test.py but only 1 inside notebook.

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[zifeo]

I've just checked, nothing in the main Jupyter console. sys.stdout.flush() doesn't change anything either.

[robertnishihara]

Interesting, I can reproduce it. The actor print statements seem to be redirected to my terminal where I ran jupyter-notebook (also it wasn't flushed immediately).

I can reproduce it even more easily in a Jupyter notebook just by running

import subprocess
subprocess.Popen(['ls'])

That will show up in the terminal where you started the jupyter-notebook and not in the notebook itself.

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[zifeo]

Still valid so far.

[robertnishihara]

@zifeo This is what I see, is that consistent with what you see?

What version of Ray are you using?