Example in the doc doesn't work on celery 4.0

[bluedazzle]

Checklist

enviroment:
Mac OS X 10.11.4
celery==4.0
redis==3.0

Steps to reproduce

example from the docs http://docs.celeryproject.org/en/latest/getting-started/first-steps-with-celery.html

from celery import Celery

app = Celery('tasks', backend='redis', broker='redis://localhost:6379/0')
app.conf.CELERY_RESULT_BACKEND = 'redis://localhost:6379/0'

@app.task
def add(x, y):
    return x + y

Expected behavior

Actual behavior

celery@MacBook-Pro.local v4.0.0 (latentcall)

Darwin-15.4.0-x86_64-i386-64bit 2016-11-11 15:36:53

[config]
.> app:         tasks:0x10270d4d0
.> transport:   redis://localhost:6379/0
.> results:     redis://localhost:6379/0
.> concurrency: 8 (prefork)
.> task events: OFF (enable -E to monitor tasks in this worker)

[queues]
.> celery           exchange=celery(direct) key=celery


[tasks]
  . task.add

[2016-11-11 15:36:53,365: INFO/MainProcess] Connected to redis://localhost:6379/0
[2016-11-11 15:36:53,375: INFO/MainProcess] mingle: searching for neighbors
[2016-11-11 15:36:54,392: INFO/MainProcess] mingle: all alone
[2016-11-11 15:36:54,405: INFO/MainProcess] celery@MacBook-Pro.local ready.
[2016-11-11 15:36:54,407: CRITICAL/MainProcess] Unrecoverable error: TypeError("can_read() got an unexpected keyword argument 'timeout'",)
Traceback (most recent call last):
  File "/usr/local/lib/python2.7/site-packages/celery/worker/worker.py", line 203, in start
    self.blueprint.start(self)
  File "/usr/local/lib/python2.7/site-packages/celery/bootsteps.py", line 119, in start
    step.start(parent)
  File "/usr/local/lib/python2.7/site-packages/celery/bootsteps.py", line 370, in start
    return self.obj.start()
  File "/usr/local/lib/python2.7/site-packages/celery/worker/consumer/consumer.py", line 318, in start
    blueprint.start(self)
  File "/usr/local/lib/python2.7/site-packages/celery/bootsteps.py", line 119, in start
    step.start(parent)
  File "/usr/local/lib/python2.7/site-packages/celery/worker/consumer/consumer.py", line 584, in start
    c.loop(*c.loop_args())
  File "/usr/local/lib/python2.7/site-packages/celery/worker/loops.py", line 88, in asynloop
    next(loop)
  File "/usr/local/lib/python2.7/site-packages/kombu/async/hub.py", line 345, in create_loop
    cb(*cbargs)
  File "/usr/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 1038, in on_readable
    self.cycle.on_readable(fileno)
  File "/usr/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 337, in on_readable
    chan.handlers[type]()
  File "/usr/local/lib/python2.7/site-packages/kombu/transport/redis.py", line 670, in _receive
    while c.connection.can_read(timeout=0):
TypeError: can_read() got an unexpected keyword argument 'timeout'

PS: celery 3.1 doesn't have the issue above.it works well

[mcsalgado]

I believe this is somewhat related to #3586, when you try to inspect active tasks before the TypeError you get:

kombu.exceptions.EncodeError: b'[[4, 4], {}, {"chain": null, "errbacks": null, "chord": null, "callbacks": null}]' is not JSON serializable

[sww]

@bluedazzle are you using the https://github.com/andymccurdy/redis-py redis library? If so, upgrading to >= 2.10.4 fixed the problem for me.

[bluedazzle]

@sww Thanks a lot! it works!

[bluedazzle]

@mcsalgado Thanks,upgrade python redis library will solve the problem,just as @sww said.

[GoodPaper]

@sww Thank you for saving time.

I add additional information about my failure case.

Environment

CentOS Linux release 7.2.1511 (Core)
python 3.4
redis 4.0.1
celery==4.0.0
redis==2.10.5

Case

1. "A" Worker get lots of task. (Transferred long time tasks.)
2. Inspect that "A" worker.
3. "A" Worker is dead(or terminated??) with log below.

File "/usr/lib/python3.4/site-packages/kombu/transport/redis.py", line 670, in _receive
    while c.connection.can_read(timeout=0):
AttributeError: 'NoneType' object has no attribute 'can_read'

Troubleshooting

1. I tried to update redis-py to 2.10.6 -> Doesn't work... Same error was occurred.
2. I tried to update celery to 4.1.0 -> It works. There is no error in inspecting workers.

Solution

So... celery==4.1.0 and redis==2.10.6 combination is worked fine to me.