CRC16 returns checksum for a given set of bytes based on the crc algorithm defined for hashing valkey keys in a cluster setup.

ParseRedirectInfo parse slot redirect information from MOVED and ASK Error.

it must be larger than any FIELD index.

write commands always go to master read from master.

read from slave if possible.

read from slave in the same idc if possible.

multi key cmd被拆分成numKeys个子请求按普通的pipeline request发送，最后在写出response时进行合并 当最后一个子请求的response到来时，整个multi key cmd完成，拼接最终response并写出 只要有一个子请求失败，都认定整个请求失败 多个子请求共享一个request sequence number 请求的失败包含两种类型：1、网络失败，比如读取超时，2，请求错误，比如本来该在A机器上，请求到了B机器上，表现为response type为error */.

ServerGroup根据cluster slots和ReadPrefer得出.