Redis 101

The aim of this talk is to give a brief introduction to Redis, and then show a few practical examples of what we can actually do with it.

First presented at the Great Western Rails meetup in Bristol, hosted by Cookpad to foster the Ruby community in the south west!

Transcript

2. What’s Redis? key / value store
3. Why Redis? It’s fast Add it, don’t switch Open source Great Ruby support
4. Who uses Redis?
5. Who uses Redis?
6. What’s Redis? key / value store
7. What’s Redis? key / string key / hash key / list key / set key / sorted set
8. key / string What can we do? • Store any data we like (up to 512MB)
9. key / string
10. Setup require "redis" redis = Redis.new(host: "192.168.0.1", port: 6380, db: 1)
11. key / string Example redis.set(key, value) redis.set "meetup:5", "Great Western Rails - May 18" => "OK" redis.get "meetup:5" => "Great Western Rails - May 18"
12. key / string Use case: Analytics redis.set request.fullpath, 0 => "OK" 10_400.times { redis.incr request.fullpath } redis.get request.fullpath => "10400"
13. key / string Rails class ApplicationController before_action :count_visit private def count_visit redis.incr(request.fullpath) end end class ProductsController < ApplicationController def show @hits = redis.get(request.fullpath) end end
14. key / hash What can we do? • Store a hash • Basically unlimited • Get specific fields • Get all fields • Increment value key: { "field1"=>"value", "field2"=>"value" }
15. key / hash Use case: Comments with voting
16. key / hash Use case: Comments with voting redis.mapped_hmset "comment:1", { body: "Wow. Great post. ", upvotes: 1, downvotes: 0 } => "OK"
17. key / hash Use case: Comments with voting redis.mapped_hmset "comment:1", { body: "Wow. Great post. ", upvotes: 1, downvotes: 0 } => "OK" redis.hincrby "comment:1", "upvotes", 1 => 2
18. key / hash Use case: Comments with voting redis.mapped_hmset "comment:1", { body: "Wow. Great post. ", upvotes: 1, downvotes: 0 } => "OK" redis.hincrby "comment:1", "upvotes", 1 => 2 upvotes = redis.hget("comment:1", "upvotes").to_i downvotes = redis.hget("comment:1", "downvotes").to_i score = upvotes - downvotes => 1
19. key / list What can we do? • Store a list (Array) • Order is maintained • Maximum length 4294967295 • Add to beginning or end, trim, get range of values
20. key / list Use case: Social media feed
21. key / list Use case: Social media feed Jane follows Tweet.where(author: current_user.following).order(created_at: :desc)
22. key / list Use case: Social media feed Jane
23. key / list Example tweet = Tweet.create(author: current_user, body: "Hello, world") tweet.author.followers.each do |follower| redis.lpush "user:#{follower.id}:feed", "tweet:#{tweet.id}" end
24. key / list Example: Most recent tweets # LRANGE key, start, stop redis.lrange "user:2:feed", 0, 9
25. key / set What can we do? • Store a unique list of members • Order not guaranteed • Check difference and intersection • Check if set contains member
26. key / set Example: Follower / Following
27. key / set Example redis.sadd "user:2:following", ["user:5", "user:1", "user:10"] => 3 redis.sadd "users:2:following", "user:10" => false redis.smembers "user:2:following" => ["user:10", "user:5", "user:1"]
28. key / set Example # Is user 2 following user 10? redis.sismember "user:2:following", "user:10" => true # Is user 2 following user 11? redis.sismember "user:2:following", "user:11" => false
29. key / set Example redis.sadd "user:10:following", ["user:4", "user:19", "user:1", "user:12"] redis.sadd "user:2:following", ["user:5", "user:1", "user:10"] # Who are both users following? redis.sinter "user:2:following", "user:10:following" => ["user:1"]
30. key / sorted set What can we do? • Similar to a set • Score for each item • Sorted! • Fetch by score
31. key / sorted set Use case: Leaderboard
32. key / sorted set Example redis.zadd "eurovision", 500, "Australia" redis.zadd "eurovision", 529, "Israel" redis.zadd "eurovision", 170, "Moldova" redis.zadd "eurovision", 0, "United Kingdom"
33. key / sorted set Example redis.zadd "eurovision", 500, "Australia" redis.zadd "eurovision", 529, "Israel" redis.zadd "eurovision", 170, "Moldova" redis.zadd "eurovision", 0, "United Kingdom" redis.zrevrange "eurovision", 0, -1, with_scores: true => [["Israel", 529.0], ["Australia", 500.0], ["Moldova", 170.0], ["United Kingdom", 0.0]]
34. Combine key / string key / hash key / list key / set key / sorted set
35. Thank you Lewis Buckley @lewispb