This is a brief, high-level overview of Redis, a networked data structure server.

1. A Brief Introduction to
Redis
Charles Anderson
!
Salem Dynamic Languages User Group
January 2014

2. Overview
• Redis is a networked “data structure
server”
• Fast, powerful, simple

3. Abstract Data Types
• In the Before Time, we didn’t have classes
and objects - we had abstract data types
•
and, we liked it!
• Procedural interface
• First (or last) parameter is the ADT

4. Example: Stack
• push(stack, item)
• pop(stack): item
• size(stack): int
• etc.

5. Stack ADT
• We had a single, global name space. So:
• stack_push(stack, item)
• stack_pop(stack)
• stack_size(stack)
• This is what the Redis API looks like

6. Redis Types
• String - scalar value
• List
• Set
• Sorted Set
• Hash

7. Redis List
• A small subset of the operations:
• LPUSH key value
• LPOP key
• LLEN key
• LRANGE key start stop

8. Redis API
• Every object has a name/key
• First parameter to each call
• Every object has a type
• Operation must match the type of object

9. Using API via CLI
$ redis-cli
redis 127.0.0.1:6379> lpush mylist 1
(integer) 1
redis 127.0.0.1:6379> lpush mylist cat
(integer) 2
redis 127.0.0.1:6379> lpush mylist 3.14
(integer) 3
redis 127.0.0.1:6379> llen mylist
(integer) 3
redis 127.0.0.1:6379> lrange mylist 0 1
1) "3.14"
2) "cat"
redis 127.0.0.1:6379> lrange mylist 0 -1
1) "3.14"
2) "cat"
3) "1"

10. Redis Clients
• The wire protocol for Redis is dead-simple
• Therefore, lots of clients for lots of
languages

11. Ruby Client Demo
irb(main):015:0> r.lpush('mylist', 1)
=> 1
irb(main):016:0> r.lpush('mylist', 'cat')
=> 2
irb(main):017:0> r.lpush('mylist', 3.14)
=> 3
irb(main):019:0> r.lrange('mylist', 0, -1)
=> ["3.14", "cat", "1"]

12. Complete Redis API
• http://redis.io/commands
• Each command includes the time
complexity of the operation - unique

13. Set
• SADD key member, SREM key member
• SCARD key
• SISMEMEBER key member
• SINTER, SUNION

14. Sorted Set
• ZADD key score member
• ZSCORE key member
• ZRANK key member
• ZRANGE key start stop
• Use case: leader board

15. Hash
• HSET key field value
• HGET key field
• HEXISTS key field, HKEYS, HLEN
• Use case: a structured record like User

16. Other Stuff
• Key Expiration
• Transactions/batches
• Publish-Subscribe
• Server-side scripting via Lua
• Replication
• Clustering

17. Implementation Details
• Everything is stored in memory
•
•
Hella fast
Not memcache - expiration is not LRU
• Persistent - tunable disk storage
• Single-threaded - simple, fast, single CPU
• Support (@antirez) is awesome

18. But, is it Web
Scale?
• NoSQL key/value store
• Kickass benchmarks
• Simpler (smaller scope) than HBase or
Cassandra
• Sharding done by clients
• Not usually a system of record
• I already work on a farm

19. More Information
• http://redis.io
• “The Little Redis Book” Seguin
• “Redis in Action” Carlson
• “Redis Cookbook” Macedo and Oliveira

20. Questions
•?