Redis 101

1. Redis 맛보기
jhoh@encoredtech.com

2. Redis
● REmote DIctionary Server
● In-memory, but can be persisted
● NoSQL Key-value store
● Written in ANSI C
● No threading, just one process

3. The Most Popular Key-Value Store

4. Why Redis?
● Fast
● Easy to learn
● Various data types
● Solve a specific set of problems
○ Good: Caching, Statistical data, Recoverable state,
Worker Queue
○ Bad: 100% consistent dataset required, Data is
larger than memory

5. Running & Connecting
● redis-server
● redis-cli
● http://try.redis.io/

6. Redis Protocol
redis[“key”] = “value”

7. Key
● Redis key is Binary safe, this means that you can use
any binary sequence as a key:
○ string
○ content of a JPEG file
○ also, empty string

8. Rules about Keys
● Too long keys are not a good idea
○ memory-wise, costly key-comparisons
● Too short keys are often not a good idea
○ more readable
○ id:10:pass => id:10:password
● Try to stick with a schema
○ “object-type:id:field” => “comment:1234:reply.to”

9. Value types
● String
● List of strings
● Sets of strings
● Sorted sets of strings
● Hashes where keys and values are strings

10. String
● The simplest Redis type
● A value can’t be bigger than 512 MB
● SET
● GET
● INCR/INCRBY, DECR/DECRBY
● GETSET

11. 127.0.0.1:6379> set mykey 100
OK
127.0.0.1:6379> get mykey
"100"
127.0.0.1:6379> incr mykey
(integer) 101
127.0.0.1:6379> incrby mykey 5
(integer) 106
127.0.0.1:6379> decr mykey
(integer) 105
127.0.0.1:6379> decrby mykey 2
(integer) 103
127.0.0.1:6379> getset mykey 1
"103"
127.0.0.1:6379> get mykey
"1"
Example Of String

12. List
● Implemented via Linked Lists
● LPUSH
○ add a new element into a list at the head
● RPUSH
○ add a new element into a list at the tail
● LRANGE

13. 127.0.0.1:6379> incr next.news.id
(integer) 1
127.0.0.1:6379> set news:1:title "Redis is simple"
OK
127.0.0.1:6379> set news:1:url "http://code.google.com/redis"
OK
127.0.0.1:6379> lpush submitted.news 1
(integer) 1
Push IDs instead of the actual data
reddit.com example:

14. Sets
● Unordered collections of unique strings
● SADD
● SMEMBERS
● SISMEMBER
● SINTER
○ the intersection between different sets

15. Sorted Sets
● Collections of unique strings with associated
score
● ZADD
○ O(log(N))
● ZRANGE/ZREVRANGE
● ZRANGEBYSCORE

16. ZADD
Add a few selected hackers with their year of birth as score
127.0.0.1:6379> zadd hackers 1940 "Alan Kay"
(integer) 1
127.0.0.1:6379> zadd hackers 1953 "Richard Stallman"
(integer) 1
127.0.0.1:6379> zadd hackers 1965 "Yukihiro Matsumoto"
(integer) 1
127.0.0.1:6379> zadd hackers 1916 "Claude Shannon"
(integer) 1
127.0.0.1:6379> zadd hackers 1969 "Linus Torvalds"
(integer) 1
127.0.0.1:6379> zadd hackers 1912 "Alan Turing"
(integer) 1

17. ZRANGE/ZREVRANGE
Ask for sorted hackers
127.0.0.1:6379> zrange hackers 0 -1
1) "Alan Turing"
2) "Claude Shannon"
3) "Alan Kay"
4) "Richard Stallman"
5) "Yukihiro Matsumoto"
6) "Linus Torvalds"
127.0.0.1:6379> zrevrange hackers 0 -1
1) "Linus Torvalds"
2) "Yukihiro Matsumoto"
3) "Richard Stallman"
4) "Alan Kay"
5) "Claude Shannon"
6) "Alan Turing"

18. Sorted Set by different ordering
● Use SORT command
○ Server will waste CPU
● Make another sorted set
○ An alternative for having multiple orders is to add
every element in multiple sorted sets at the same
time.

19. Updating the scores
● Just calling again ZADD

20. Hashes
● HSET
● HGET
● HGETALL
● HKEYS

21. 127.0.0.1:6379> hset users:1 username poby
(integer) 1
127.0.0.1:6379> hget users:1 username
"poby"
127.0.0.1:6379> hmset users:1 age 10 bestfriend pororo
OK
127.0.0.1:6379> hgetall users:1
1) "username"
2) "poby"
3) "age"
4) "10"
5) "bestfriend"
6) "pororo"
127.0.0.1:6379> hkeys users:1
1) "username"
2) "age"
3) "bestfriend"
127.0.0.1:6379> hdel users:1 age
(integer) 1
Example Of Hash

22. Redis Clients
http://redis.io/clients

23. Demo: realtime-info
AWS ElastiCache
realtime-info
EDM1
EDM1
EDM1
EDM1
EDM1
EDM1
API Server
Log Server

24. Demo: Realtime-Info (1)
SET realtime-info by Poby

25. Demo: Realtime-Info (2)
MGET realtime-info by API

26. 참고 자료
● Redis - Wikipedia
● Redis - Fast and Furious
● 15 minutes introduction to Redis data types
● The Little Redis Book
● redis.io

27. 끝