The problem/use-case that the feature addresses

Lua operations that are readonly can run on replicas. However command info for evalsha and eval tell that they can be write commands. Redis clients use this information to route to replica or master. Evalsha is routed to masters since it's not a read only command. This primarily is for redis in cluster mode.

Description of the feature

Similar to GEORADIUS_RO, introduce EVAL_RO and EVALSHA_RO that are readonly versions of EVAL and EVALSHA.

Alternatives you've considered

Modifying client library to explicitly route calls to replica nodes.

Additional information

Have made a contribution on go-redis to explicitly read from replicas redis/go-redis#1581