redis/redis-rb · error · Redis::Distributed::CannotDistribute

MAPPED_MSET cannot be used in Redis::Distributed because the

Error message

MAPPED_MSET cannot be used in Redis::Distributed because the keys involved need to be on the same server or because we cannot guarantee that the operation will be atomic.

What it means

Error "MAPPED_MSET cannot be used in Redis::Distributed because the keys involved need to be on the same server or because we cannot guarantee that the operation will be atomic." thrown in redis/redis-rb.

Source

Thrown at lib/redis/distributed.rb:331

    end

    # Set the time to live in milliseconds of a key.
    def psetex(key, ttl, value)
      node_for(key).psetex(key, ttl, value)
    end

    # Set the value of a key, only if the key does not exist.
    def setnx(key, value)
      node_for(key).setnx(key, value)
    end

    # Set multiple keys to multiple values.
    def mset(*)
      raise CannotDistribute, :mset
    end

    def mapped_mset(_hash)
      raise CannotDistribute, :mapped_mset
    end

    # Set multiple keys to multiple values, only if none of the keys exist.
    def msetnx(*)
      raise CannotDistribute, :msetnx
    end

    def mapped_msetnx(_hash)
      raise CannotDistribute, :mapped_msetnx
    end

    # Get the value of a key.
    def get(key)
      node_for(key).get(key)
    end

    # Get the value of a key and delete it.
    def getdel(key)

View on GitHub (pinned to 2ba9010b91)

Solutions

1. Do not use mapped_mset on Redis::Distributed; the keys may hash to different servers.
2. Iterate the hash and call set for each key/value pair so routing stays per-key.

When it happens

Trigger: Thrown at lib/redis/distributed.rb:331 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of redis/redis-rb@2ba9010b91 (2026-08-23). Data as JSON: /api/errors/d9f6a95367df80eb. Report an issue: GitHub.