redis-key_hash (0.0.2)

jhwillett
2017-08-29T17:03:47Z

redis-key_hash provides tests of key hash slot agreement for use with
Redis Cluster and RedisLabs Enterprise Cluster.

Redis Cluster (RC) and RedisLabs Enterprise Cluster (RLEC) both
require that all keys in multi-key operations hash to the same node.
They use slightly different default hashing algorithms and RLEC offers
customizable hash pattersn.

It is impossible to predict which nodes will host each shard, and
difficult to predict which slot will host each key. But it is easy to
identify the key hash tag which RC or RLEC will use to select a shard.
Where key hash tags agree, we can be certain that slots and nodes will
also agree - even if hash tag disagreement does not always imply slot
or node disagreement.

By pulling this check into Ruby we can arrange to fail fast, before
sending a command to Redis which is at risk of CROSSLOT failure. We
can also validate key management schemes in unit tests which run
without support services or with a non-sharded Redis.