Redis

Redis = Remote Dictionary Server. Usually used as cache.

Can be used as a “buffer” between endpoint and multiple app servers.

Concepts

• Pub/Sub
• Transactions
• LRU
• Leader vs Follower server
• Redis Cluster, sharding
• Redis Sentinel, self-healing

Usage

SET name "Samuel"
GET name
 
SET user:sghuang:city "South Bend"
 
SET visits 0
INCR visits
INCRBY visits 2
 
MSET score:seahawks 43 score:brocos 8
 
EXISTS name  // returns 1 or 0
DEL name
 
SET color blue XX  // set only if the key exists
SET color blue NX  // set if does not exist
 
SET name "Samuel" EX 3600  // TTL, use PX for miliseconds
 
TYPE visits  // everything is a string
 
RPUSH notifications "N1" "N2" "N3"  // array
LRANGE notifications 0 -1
RPOP notifications  // also LPOP
LTRIM and RTRIM
 
HMSET sghuang title "X" name "X"
HGET sghuang name
HGETALL and HINCR
 
SADD colors red blue ...
SISMEMBER colors red
SMEMBERS colors
SPOP colors
 
ZADD ordinals 3 third  // sorted set 
ZADD ordinals 1 first
 
EVAL "for i = 0,9,1 do redis.call('SET', 'lua_key' .. i, i * 5) end" 0

Be aware of the thundering-herd.

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