MOVED communication protocol_error ai_generated true

MOVED 12182 10.0.0.1:6379: Redis cluster redirect to different node

ID: communication/redis-cluster-moved-redirect

Also available as: JSON · Markdown · 中文
88%Fix Rate
86%Confidence
1Evidence
2023-09-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Redis 6.2 active — — —
Redis 7.0 active — — —
Redis 7.2 active — — —
ioredis 5.3 active — — —
redis-py 4.5 active — — —

Root Cause

Redis cluster client sent a command to a node that does not own the key's hash slot, and the client is not using smart client-side routing or cluster-aware connection pooling.

generic

中文

Redis 集群客户端将命令发送到不拥有该键哈希槽的节点，且客户端未使用智能客户端路由或集群感知的连接池。

Official Documentation

https://redis.io/docs/reference/cluster-spec/

Workarounds

  1. 95% success Use a Redis cluster-aware client library that automatically handles MOVED redirections, e.g., ioredis Cluster: `new Redis.Cluster([{ host: '10.0.0.1', port: 6379 }])` which maintains a slot-to-node mapping. 
    Use a Redis cluster-aware client library that automatically handles MOVED redirections, e.g., ioredis Cluster: `new Redis.Cluster([{ host: '10.0.0.1', port: 6379 }])` which maintains a slot-to-node mapping.
  2. 90% success Enable cluster mode in the client configuration with automatic slot refresh, e.g., in redis-py: `rediscluster.RedisCluster(startup_nodes=[{'host':'10.0.0.1','port':6379}], skip_full_coverage_check=True)`. 
    Enable cluster mode in the client configuration with automatic slot refresh, e.g., in redis-py: `rediscluster.RedisCluster(startup_nodes=[{'host':'10.0.0.1','port':6379}], skip_full_coverage_check=True)`.
  3. 75% success If using a non-cluster-aware client, implement manual retry with slot calculation: compute the hash slot for the key using CRC16 modulo 16384, then connect to the correct node directly. 
    If using a non-cluster-aware client, implement manual retry with slot calculation: compute the hash slot for the key using CRC16 modulo 16384, then connect to the correct node directly.

中文步骤

  1. 使用支持 Redis 集群的客户端库自动处理 MOVED 重定向，例如 ioredis Cluster：`new Redis.Cluster([{ host: '10.0.0.1', port: 6379 }])`，它会维护槽到节点的映射。
  2. 在客户端配置中启用集群模式并自动刷新槽信息，例如在 redis-py 中：`rediscluster.RedisCluster(startup_nodes=[{'host':'10.0.0.1','port':6379}], skip_full_coverage_check=True)`。
  3. 如果使用非集群感知客户端，实现手动重试并计算槽位：使用 CRC16 对键取模 16384 计算哈希槽，然后直接连接到正确节点。

Dead Ends

Common approaches that don't work:

  1. Manually redirect the client to the node IP in the MOVED error without updating the cluster topology 70% fail

    The cluster topology may change again; manual redirection is not scalable and can cause further MOVED errors.

  2. Disable cluster mode and connect to a single Redis instance 90% fail

    Defeats the purpose of clustering; data may be incomplete or inconsistent across nodes.

  3. Increase connection timeout in client configuration 85% fail

    Timeout does not address the routing issue; MOVED is a protocol-level redirect, not a timeout.