Maintain determinstic ordering of replica(s) in CLUSTER SLOTS response

[hpatro]

Sort clusterNode.slaves while adding a new replica to the cluster on basis of name. This will enable deterministic ordering of replica(s) information in CLUSTER SLOTS response.

Before this change:

127.0.0.1:6380> CLUSTER SLOTS
1) 1) (integer) 0
   2) (integer) 16383
   3) 1) "127.0.0.1"
      2) (integer) 6379
      3) "fc72609a620c62d073a31eed9ddde5104c1fa302"
      4) (empty array)
   4) 1) "127.0.0.1"
      2) (integer) 6381
      3) "fac84bbf2ffc5cfcdebc92c06b8ead9c3cba4051"
      4) (empty array)
   5) 1) "127.0.0.1"
      2) (integer) 6380
      3) "b1249d394326f1485df0b895f2fd38e141aa5056"
      4) (empty array)

After this change:

127.0.0.1:6380> CLUSTER SLOTS
1) 1) (integer) 0
   2) (integer) 16383
   3) 1) "127.0.0.1"
      2) (integer) 6379
      3) "fc72609a620c62d073a31eed9ddde5104c1fa302"
      4) (empty array)
   4) 1) "127.0.0.1"
      2) (integer) 6380
      3) "b1249d394326f1485df0b895f2fd38e141aa5056"
      4) (empty array)
   5) 1) "127.0.0.1"
      2) (integer) 6381
      3) "fac84bbf2ffc5cfcdebc92c06b8ead9c3cba4051"
      4) (empty array)

ref: redis/redis#13149

[zuiderkwast]

Thanks for migrating this one!

It'd be nice to add a test case that verifies that the responses are identical from all nodes in the cluster.

[hpatro]

It'd be nice to add a test case that verifies that the responses are identical from all nodes in the cluster.

@zuiderkwast Actually we do compare CLUSTER SLOTS response across nodes in lot's of TCL tests via cluster_config_consistent. However, the issue which exists in the TCL tests is we never wait enough for the replica(s) to be online and surface in CLUSTER SLOTS output.

@VoletiRam is fixing the cluster_config_consistent to wait until replica(s) are online. And that should cover your request.

[madolson]

This was broadly approved before the switch over, so I think it's safe to move forward with it now. We should update the docs page though for it.