Some setbacks here, clients are not so complete:

• RedisArray does not support SSCAN, you'll get:
  Parameter 2 to Redis::sscan() expected to be a reference, value given
• Predis alos have limited SSCAN and gives the following if key does not exists:
  Predis\Response\ServerException: ERR no such key

These can potentially be fixed by instead using SMEMBERS + skipping SSCAN/SMEMBERS on tagId if RENAME returned 0 (not found in this case).

More of a Server issue:

• Cluster on Predis and RedisCluster does not support RENAME:
  RedisCluster::rename(): Keys don't hash to the same slot

This one I'm unsure of, should we try to make sure we RENAME within same node?

Suggestions @nicolas-grekas / @berezuev?

Can't we rename to a key that will be guaranteed on the same node, using the special syntax they support for this?

using the special syntax they support for this?

Do you happen to remember where that is described? Thought about that too, but didn't know where to look.

Sure, see https://redis.io/topics/cluster-spec, the section about "hash tags"

is it possible to have { and } in our normal tagId Redis keys ? If yes, we won't be able to use hash tags to achieve our goal.
Otherwise, this can indeed by used, making the temporary tag id being '{'.$tagId.'}'.$randomSuffix instead of $tagId.':'.$randomSuffix.

The alternative could be to talk directly to the corresponding node in the cluster. That's possible AFAIK.

I think there is a function for that :)
Happy 🌴 !

RedisCluster failure was fixed in be04079. I did not find a simple way to deal with RENAME on Predis across RedisCluster & PredisCluster so left that as-is, could instead use SPOP there if prefered.

AppVeyor failure seems unrelated (HttpClient\Tests\NativeHttpClientTest::testNotATimeout), so rebased and moving this to review.

let's throw for now in this situation and open an issue on Predis?

last commit 2017...

Another reason to throw and encourage using phpredis...
Let's still create the issue for the record...

Mergeable?

IMHO Yes, we can do the improvements as a follow up, it will anyway need some investigation and testing. But it's entirely up to you two.

I'd prefer doing it in this PR, depending on your availability to do it :)

Hello, I just push-forced this here:
https://github.com/symfony/symfony/compare/db80b9db0519ec73165b9bc2d57674993c7a3d5e..28948eeb8b

Should fix the last comment.

Exception on rename on missing key

Actually, I just discovered this is already possible! PR updated to use pipelining.

Lack of api to find slot of key when using RedisCluster

that's a bit more involving, as that'd require implementing the logic to react to MOVE responses. Should be handled at the Predis level instead, as phpredis does.

Thank you @andrerom.