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What on Earth is Redis?

Redis Keys

  • Binary Safe (if it can be converted into binary, you can store it)
  • 512 MB max
  • whatever you want
    • stick to a schema:
      • users:justincastilla:followers
      • weather:94606:02:23:1730
      • location:574:product:7743854

Strings

  • SET/GET strings and numbers
    • Redis detects the differences
  • INCR, DECR, INCRBY, DECRBY
  • TTL (time-to-live) with SET key EX value

Lists

  • Push/Pop functionality, but from either end
  • Great for implementing Stacks and Queues

Queue example: Housekeeping

Scenario: Front-Desk receives requests for service from guests. They enter the reqeusts into a queue backed by Redis and the housekeepers receive notifications of the requests in the order they were created.

# Producer (Front-Desk)
> LPUSH jobs '{"room": 101,"job": "Cleaning"}'
> LPUSH jobs '{"room": 309,"job": "Taxi"}'
> LPUSH jobs '{"room": 484,"job": "Extra Towels"}'
# Consumer (Housekeepers)
> RPOP jobs
"{\"room\": 101,\"job\": \"Cleaning\"}"

Sorted Set

Adding members and scores to a sorted set:

$ redis-cli
> ZADD team_scores 23740 Brian
 (integer) 1
> ZADD team_scores 12010 Guy 56750 Justin 78130 Simon 66320 Steve 86590 Suze
(integer) 5

Let's read the sorted set back:

> ZRANGE team_scores 0 -1
1) "Guy"
2) "Brian"
3) "Justin"
4) "Steve"
5) "Simon"
6) "Suze"

That only gives us the names, and in order from lowest to highest :/. Let's reverse the order and get scores as well:

ZRANGE team_scores 0 -1 REV WITHSCORES
 1) "Suze"
 2) "86590"
 3) "Simon"
 4) "78130"
 5) "Steve"
 6) "66320"
 7) "Justin"
 8) "56750"
 9) "Brian"
10) "23740"
11) "Guy" 
12) "12010"

Suze is #1!