[Serve] router cast replicas set to list for random sample in python 3.11

[GeneDer]

Why are these changes needed?

Python 3.11 has a breaking change enforcing the type of random.sample() to be a list. Cast the candidate_replica_ids to list before feeding into the function.

Related issue number

Closes #37765

Checks

• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[edoakes]

are you testing on 3.11? 🤔

[GeneDer]

oh no haha, this came from a user who tried serve on experimental python 3.11 #37765 I just thought it's a quick patch so go ahead and raised the PR 🙂

[ddelange]

@edoakes could you cherry-pick this one?

on ray 2.6.2:

  File "/Users/ddelange/.pyenv/versions/3.11.0/envs/vv311/lib/python3.11/site-packages/ray/serve/_private/router.py", line 404, in choose_two_replicas_with_backoff
    chosen_ids = random.sample(
                 ^^^^^^^^^^^^^^
  File "/Users/ddelange/.pyenv/versions/3.11.0/lib/python3.11/random.py", line 436, in sample
    raise TypeError("Population must be a sequence.  "
TypeError: Population must be a sequence.  For dicts or sets, use sorted(d).

[edoakes]

@ddelange unfortunately 2.6.3 has sailed and that's the last patch release before 2.7

Hopefully we start testing python 3.11 soon...

[ddelange]

Hi @edoakes 👋 will ray 2.7 release from master branch?

[edoakes]

@ddelange a release branch will be cut from master today (Friday, Aug 25th). So everything currently in master will be included.

Btw, we've added a basic Python 3.11 release test to avoid breakages now