Ray does not work with most recent version of redis

[devin-petersohn]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Multiple
• Ray installed from (source or binary): source (current master)
• Ray version: -
• Python version: Multiple
• Exact command to reproduce: ray.init()

Describe the problem

Multiple people have installed Modin and are receiving this error. modin-project/modin#259

redis.exceptions.DataError: Invalid input of type: 'NoneType'. Convert to a byte, string or number first.

I was able to reproduce by running

pip install -U redis

And then

import ray
ray.init()

Redis recently released. I believe we need to pin Ray to a specific version of the library dependencies for compatibility purposes.

[simon-mo]

I can re-produce this. A temporary fix will be:

pip install -U redis==2.10.6

[devin-petersohn]

I removed the release-blocker tag since we have pinned Ray to version 2.10.6. We can investigate upgrading redis after the release.

[richardliaw]

This issue has come up multiple times; should we pin?

[robertnishihara]

@richardliaw, we already have in #3333.

I think the next step is to just fix the issue.

[robertnishihara]

I'll take a quick look at it now.

[devin-petersohn]

Closed via #3379