Get more than a cache back! - ConFoo Montreal
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Redis is an open source, in-memory key-value data store that can be used as a cache or database. It supports various data structures like strings, hashes, lists, sets and sorted sets. Redis has features for transactions, pub/sub messaging and scripting. Data can be sharded across multiple Redis instances for large datasets or high throughput needs. Common use cases include caching, sessions, pub/sub, rate limiting and autocompletion.
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Get more than a cache back! - ConFoo Montreal
- 1. RedisGet more than a cache back! Maarten Balliauw @maartenballiauw
- 2. Who am I? Maarten Balliauw Antwerp, Belgium Developer Advocate, JetBrains Founder, MyGet Focus on web & cloud http://blog.maartenballiauw.be @maartenballiauw
- 4. Redis
- 5. Redis “Redis is an open source, BSD licensed, networked, single-threaded, in-memory key- value cache and store. It is often referred to as a data structure server since keys can contain strings, hashes, lists, sets, sorted sets, bitmaps and hyperloglogs.” REmote DIctionary Server
- 6. Redis Key-value cache and store (value can be a couple of things) In-memory (no persistence, but you can) Single-threaded (atomic operations & transactions) Networked (it’s a server and it does master/slave) Some other stuff (scripting, pub/sub, Sentinel, snapshot, …) Things to remember
- 7. Persistence? Dump memory to disk (faster restore after restart) AOF (append-only files) RDB (Redis DB snapshots) With or without: all your data must fit in memory
- 9. The Little Redis Book http://openmymind.net/redis.pdf By Karl Seguin
- 10. Data types Type Example Key Example value String cache:/home <html><head><title>Home page</title> Hash categories:1 Field name description numproducts Member Ships Pirate ships for sale 50000 Set categories:1:products 20 11 56 89 32 4 List products:20:comments [0] -> “That skull flag is awesome!” [1] -> “Parrot bit my finger, not happy!” [2] -> “Parrot keeps swearing at me.” Sorted set products:bestsellers Field Eye Patch Parrot Score 84632 82120 + Bitmap, Hyperloglog
- 11. Data types demo
- 12. Data types Type Example Key Example value String cache:/home user:nextid <html><head><title>Home page</title> 2 Hash user:1 Field name handle Member Maarten @maartenballiauw Set user:1:followers 10 42 99 85 List user:1:timeline [0] -> { ... } [1] -> { ... } [2] -> { ... } Sorted set trending:no:tags Field #ndcoslo #redis Score 84632 82120 + Bitmap, Hyperloglog
- 13. Keys Good practice: use a pattern for keys E.g. users:1:maarten Get by id: KEYS users:1:* GET ...... Get by name: KEYS users:*:maarten GET ...... O(N) operation – use with caution!
- 14. But... client-side? Lots of options! http://www.redis.io/clients
- 15. Connecting to Redis (C# / Node – pick one!) demo
- 16. Transactions MULTI, EXEC, DISCARD, WATCH No rollbacks (just discard queue) Failures are because of you, not Redis Optimistic locking with WATCH Only execute transaction queue if watched keys did not change
- 18. Pub/Sub (P)SUBSCRIBE, UNSUBSCRIBE, PUBLISH Subscribe to a queue SUBSCRIBE news (or PSUBSCRIBE news:*) Send data to a queue PUBLISH news “This just in!” (optional) Keyspace notifications http://www.redis.io/topics/notifications CONFIG SET notify-keyspace-events KEA PSUBSCRIBE '__key*__:*' (or __keyspace@0__:foo)
- 19. Pub/Sub demo
- 20. Scripting Run Lua scripts on Redis http://www.redis.io/commands/eval EVAL ‘return “Hello, World!”’ 0 Scripts are cached (SCRIPT FLUSH) Scripts can be used as functions Although we must pass the body all the time (or use SCRIPT LOAD + EVALSHA) Helper functions available! Base, table, string, math, debug, struct, cjson, cmsgpack, redis.sha1hex
- 21. Scripting demo
- 22. What if I need more memory? Sharding On client (consistent hashing) Using a proxy (Twemproxy - https://github.com/twitter/twemproxy) Cluster On server (Redis Cluster) tip: always connect to >= 2 nodes var Redis = require('ioredis'); var cluster = new Redis.Cluster([ { port: 6380, host: '127.0.0.1' }, { port: 6381, host: '127.0.0.1' } ]); cluster.set('foo', 'bar'); cluster.get('foo', function (err, res) { // ... });
- 23. Patterns
- 24. When can I use Redis? Output cache Session state General-purpose cache (e.g. for database) “Cache with benefits” Pub/sub Generally: when use case maps and data fits in RAM
- 25. When should I avoid Redis? More data than can fit in RAM Can use multiple, but even then: SUM(RAM) == max. data size Data and query model fits well in a relational model Materialize certain queries in Redis if needed Avoid Redis for large objects... ...with lots of concurrent read/write operations
- 26. Counting stuff How would you count “likes” if you were Facebook? SQL UPDATE posts SET likes = likes + 1 WHERE postid = 1234 Locking! Will slow down the application... Redis INCR post:12345 (Every once in a while, check keys to persist)
- 27. Counting stuff (+ popularity) And how would you get the 5 most popular posts? Use a sorted set Elements are scored (= # of likes) We can use ZREVRANGE to get the top X posts ZREVRANGE posts:likes 0 5 withscores
- 28. Get the latest 5 product reviews No need to go to the database! Use a Redis List, truncated at 5 items Need more? Query the database
- 29. Rate limiting API should only allows 5 requests per 60 seconds Redis List Record 5 latest requests If we’re at 5, check the leftmost item versus current time 1 2 3 4 5 12:20:25 12:20:22 12:20:21 12:20:18 12:19:50
- 30. Autocompletion How to provide autocompletion over our million- records product catalog? SQL “LIKE” Lucene / ElasticSearch Redis Sorted Set
- 31. Intersecting collections “Which friends do we have in common?” Algorithm could be: Find friends that we have in common Find friends they have in common Score the # of connections
- 32. Sort We have a series of bugs Priority, Status, Title, ... A user follows a few of these bugs How to store? How to query? (give me my top 5 bugs by priority) hset bugs:1 priority 5 hset bugs:2 priority 2 hset bugs:3 priority 1 SORT bugsifollow BY bugs:*->priority
- 33. Conclusion
- 34. Conclusion Redis is not just a cache Data types Transactions Pub/sub Scripting Sharding/partitioning Patterns 1 thing to remember: http://openmymind.net/redis.pdf
Editor's Notes
- Start server Show config file and some of the options in there Connect client, mention on localhost it autoconnects as I’m using default ports and such Run some commands: get name set name “Maarten” get name getrange name 2 4 expire name 5 get name Explain simple commands, yet powerful (e.g. substring) Check config with “info” (also cache misses/hits etc.)
- Demo some of the data types. Here’s a bunch to choose from: String: get cache:/home set cache:/home "Home page" get cache:/home getrange cache:/home 2 5 expire cache:/home 5 get cache:/home incr site:visits incrby site:visits 6 Hash: hmset categories:1 name Books numproducts 4 hgetall categories:1 hincrby categories:1 numproducts 1 hget categories:1 name hset categories:1 numproducts 500 hgetall categories:1 Set: sadd categories:1:products 20 11 56 89 32 4 sadd categories:1:products 99 scard categories:1:products sadd categories:2:products 20 11 sinter categories:1:products categories:2:products sdiff categories:1:products categories:2:products List: rpush products:20:comments "Awesome product!" rpush products:20:comments "This sucks." rpush products:20:comments "Yarr!" lindex products:20:comments 1 llen products:20:comments brpop products:20:comments queue 0 #blocking at the end! pub/sub? Sorted Set: zadd products:bestsellers 100 "Eye Patch" 10 "Parrot" 1 "Ship" zrevrange products:bestsellers 0 1 zrevrank products:bestsellers "Ship" zscore products:bestsellers "Ship"
- Ask which tech (C# or Node)
- Connect to localhost, perhaps flushall first SET where “Sweden” SET conference “Unknown” SET attendees 0 Connect a second client MULTI INCRBY attendees 100 SET conference “CloudBurst” EXEC Worked fine! Now let’s do this on client 1: WATCH attendees MULTI INCRBY attendees 100 And on client 2: SET attendees 99 And on client 1: EXEC .NET: var transaction = redis.GetDatabase().CreateTransaction(); transaction.AddCondition(Condition.KeyExists("foo")); transaction.StringSetAsync("foo", "bar"); bool committed = transaction.Execute();
- Use two clients Client 1: SUBSCRIBE news Client 2: PUBLISH news “This just in” Let’s do that in .NET: ConnectionMultiplexer redis = ConnectionMultiplexer.Connect("localhost:6379"); ISubscriber subscriber = redis.GetSubscriber(); subscriber.Subscribe("news", (channel, message) => { Console.WriteLine("News: {0}", (string)message); }); ISubscriber publisher = redis.GetSubscriber(); publisher.Publish("news", "This just in!"); Console.ReadLine(); Send a message from one of the clients, too Keyspace notifications: CONFIG SET notify-keyspace-events KEA PSUBSCRIBE '__key*__:*'
- Do some scripts in the sample project