Introduction to Redis
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Redis is an open source in memory database which is easy to use. In this introductory presentation, several features will be discussed including use cases. The datatypes will be elaborated, publish subscribe features, persistence will be discussed including client implementations in Node and Spring Boot. After this presentation, you will have a basic understanding of what Redis is and you will have enough knowledge to get started with your first implementation!
![PUBLISH SUBSCRIBE
HOW DOES IT WORK
• SUBSCRIBE [channel]
• UNSUBSCRIBE [channel]
• PUBLISH [channel] [message]
Channel can contain
glob patterns like news.*](https://image.slidesharecdn.com/introductionredis-180409191817/85/Introduction-to-Redis-23-320.jpg)
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Introduction to Redis
- 2. INTRODUCTION REDIS INTRODUCING REDIS DATATYPES PUBLISH SUBSCRIBE PERSISTENCE TRANSACTIONS REJSON AND REDISEARCH CLIENTS
- 3. 1 2 3 What is Redis Why use Redis Who uses Redis INTRODUCTION REDIS
- 4. INTRODUCING REDIS • Redis First release 2009 An open-source in-memory database project implementing a distributed, in-memory key-value store with optional durability.
- 5. INTRODUCING REDIS • Redis is an open source, in-memory data structure store Can be used as Database, Cache, Message broker • NoSQL Key/Value store • Supports multiple data structures • Features like • Transactions • Pub/Sub • Scalability / availability options • Time to live for entries Mostly single threaded! Modules can be multi threaded
- 6. TYPICAL USES OF REDIS • Cache database query results • https://redislabs.com/ebook/part-1-getting-started/chapter-2-anatomy-of-a-redis-web-application/2-4- database-row-caching/ • Cache entire webpages (e.g. Wordpress) • https://wordpress.org/plugins/redis-cache/ • Use for HTTP session store • https://docs.spring.io/spring-session/docs/current/reference/html5/ • Cache logins / cookies • https://redislabs.com/ebook/part-1-getting-started/chapter-2-anatomy-of-a-redis-web-application/2-1- login-and-cookie-caching/
- 7. WHY REDIS? • Very flexible • Very fast • Caching & Disk persistence • No schemas, column names • Rich Datatype Support
- 8. HOW TO USE REDIS EXAMPLE: CACHE DB RESULTS Clients Back-end / server side Persistent storage Cache
- 9. WHO USES REDIS Azure Redis Cache
- 10. WHO USES REDIS IN THE NETHERLANDS
- 11. 1 2 3 Strings and expiry Lists, Sets, Hashes Sorted sets DATATYPES
- 12. DATATYPES • Strings • Lists • Sets • Sorted sets • Hashes • Bitmaps • Hyperlogs • Geospatial indexes Datatypes cannot be nested! E.g. no lists of hashes You can name your variables like: person:1 person:2 KEYS person:* gives all person variables The KEYS command is blocking. Better to keep a set or list of person keys
- 13. STRINGS • Max size 512Mb • Byte save. Can store binaries • Use cases: • Store JPEG’s • Store serialized objects • Example usage 127.0.0.1:6379> SET greeting ‘Hello’ OK 127.0.0.1:6379> GET greeting “Hello” 127.0.0.1:6379> DEL greeting (integer) 1 127.0.0.1:6379> EXISTS greeting (integer) 0
- 14. EXPIRY • Expiry can be set for existing variables 127.0.0.1:6379> SET greeting “Hello” OK 127.0.0.1:6379> EXPIRE greeting 10 (integer) 1 127.0.0.1:6379> TTL greeting (integer) 8 127.0.0.1:6379> GET greeting “Hello” 127.0.0.1:6379> GET greeting (nil)
- 15. EXPIRY • Expiry can be set when a variable is created and expiry can be removed 127.0.0.1:6379> SETEX greeting 10 “Hello” OK 127.0.0.1:6379> TTL greeting (integer) 8 127.0.0.1:6379> PERSIST greeting OK 127.0.0.1:6379> TTL greeting (integer) -1
- 16. LISTS • A list of Strings • Max size 4294967295 • Can for example be used for • timelines of social networks • Speed • Actions at the start or end of the list are very fast. • Actions in the middle are a little less fast 127.0.0.1:6379> LPUSH people “Maarten” (integer) 1 127.0.0.1:6379> RPUSH people “John” (integer) 2 127.0.0.1:6379> LRANGE people 0 -1 1) “Maarten” 2) “John” 127.0.0.1:6379> LLEN people (integer) 2 127.0.0.1:6379> LPOP people “Maarten” 127.0.0.1:6379> RPOP people “John”
- 17. SETS • Unordered collection of Strings • Does not allow repeated elements • Useful for tracking unique items • Allows extracting random members Using SPOP, SRANDMEMBER • Useful for intersects and diffs 127.0.0.1:6379> SADD cars “Honda” (integer) 1 127.0.0.1:6379> SADD cars “Ford” (integer) 1 127.0.0.1:6379> SADD cars “Honda” (integer) 0 127.0.0.1:6379> SISMEMBER cars “Honda” (integer) 1 127.0.0.1:6379> SISMEMBER cars “BMW” (integer) 0 127.0.0.1:6379> SMEMBERS cars 1) “Ford” 2) “Honda” 127.0.0.1:6379> SMOVE cars mycars “Honda” (integer) 1 127.0.0.1:6379> SDIFF cars mycars 1) “Ford”
- 18. HASHES • Maps between string fields and values • Ideal for storing objects 127.0.0.1:6379> HMSET user:1000 username antirez password P1pp0 age 34 OK 127.0.0.1:6379> HGETALL user:1000 1) “username” 2) “antirez” 3) “password” 4) “P1pp0” 5) “age” 6) “34” 127.0.0.1:6379> HSET user:1000 password 12345 (integer) 0 127.0.0.1:6379> HGET user:1000 password “12345” 127.0.0.1:6379> HKEYS user:1000 1) “username” 2) “password” 3) “age”
- 19. SORTED SETS • Non repeating collections of Strings • Every member has a score. • Members are unique. Scores are not • Ordering is from small to large score • Ordering for items with the same score is alphabetic • Useful for leader boards or autocomplete 127.0.0.1:6379> ZADD myzset 1 "one" (integer) 1 127.0.0.1:6379> ZADD myzset 1 "one" (integer) 0 127.0.0.1:6379> ZADD myzset 1 "uno" (integer) 1 127.0.0.1:6379> ZADD myzset 2 "two" 3 "three" (integer) 2 127.0.0.1:6379> ZRANGE myzset 0 -1 WITHSCORES 1) "one" 2) "1" 3) "uno" 4) "1" 5) "two" 6) "2" 7) "three" 8) "3" 127.0.0.1:6379> ZRANGE myzset 0 0 1) "one"
- 20. 1 2 PERSISTENCE Redis Database File (RDB) Append Only File (OAF)
- 21. PERSISTENCE RDB (Redis Database File) AOF (Append Only File) Provides point in time snapshots Logs every write Creates complete snapshot at specified interval Replays at server startup. If log gets big, optimization takes place File is in binary format File is easily readable On crash minutes of data can be lost Minimal chance of data loss Small files, fast (mostly) Big files, ‘slow’ https://www.slideshare.net/eugef/redis-persistence-in-practice-1
- 22. 1 2 PUBLISH SUBSCRIBE How to use it Things to mind
- 23. PUBLISH SUBSCRIBE HOW DOES IT WORK • SUBSCRIBE [channel] • UNSUBSCRIBE [channel] • PUBLISH [channel] [message] Channel can contain glob patterns like news.*
- 24. PUBLISH SUBSCRIBE THINGS TO MIND • A missed message has been missed permanently. No retry • There is no history of messages Like a JMS topic without durable subscribers
- 25. 1 2 TRANSACTIONS
- 26. TRANSACTIONS • Not like relational database transactions! • Start a transaction: MULTI Commands after MULTI are queued • Execute the queued commands: EXEC All or none of the commands are executed However, if one fails, the others are still executed • Make EXEC conditional: WATCH EXEC will only execute if watched variables are unchanged WATCH zset element = ZRANGE zset 0 0 MULTI ZREM zset element EXEC There is no ZPOP but it can be implemented like below Redis LUA scripts are also executed in a transaction
- 27. 1 2 JSON AND SEARCH ReJSON RediSearch
- 28. REDIS AS A JSON STORE JSON support can be implemented by adding the ReJSON module from Redis Labs 127.0.0.1:6379> JSON.SET scalar . '"Hello JSON!"' OK 127.0.0.1:6379> JSON.SET object . '{"foo": "bar", "ans": 42}' OK 127.0.0.1:6379> JSON.GET object "{"foo":"bar","ans":42}" 127.0.0.1:6379> JSON.GET object .ans "42" https://redislabs.com/blog/redis-as-a-json-store/
- 29. REDISEARCH - REDIS POWERED SEARCH ENGINE Auto completion 127.0.0.1:6379> FT.SUGADD autocomplete “hello world” 100 OK 127.0.0.1:6379> FT.SUGGET autocomplete “he” 1) "hello world“ Full text search 127.0.0.1:6379> FT.ADD myIdx doc1 1.0 FIELDS title “hello” body “bla” url “http://redis.io” OK 127.0.0.1:6379> FT.SEARCH myIdx “hello world” LIMIT 0 10 1) (integer) 1 2) “doc1” 3) 1) “title” 2) “hello” 3) “body” 4) “bla” 5) "url” 6) “http://redis.io” http://redisearch.io/Quick_Start/ docker run -p 6379:6379 redislabs/redisearch:latest
- 30. 1 2 CLIENTS Node.js Spring Boot
- 31. CLIENTS NODE.JS Create a client and connect Create an event handler Subscribe to a channel
- 32. CLIENTS SPRING BOOT • There is no annotation available to • Create a container • Register a listener to the container • Register a receiver to the listener • This requires more code than for example listening to a Kafka topic https://spring.io/guides/gs/messaging-redis/
- 33. CLIENTS SPRING BOOT Wait for a single message
- 35. SOME THINGS TO MIND IN PRODUCTION • Redis is single threaded • Want to use more CPU’s? Use more Redis instances! • Requests are blocking. Be careful with for example KEYS commands. Mind the time complexity of operations! • Mind the number of connections! • Implement a proxy, for example twemproxy (manages persistent connections) • Snapshotting is blocking • Investigate persistence requirements and consider rolling BGSAVE, OAF instead of snapshotting http://tech.trivago.com/2017/01/25/learn-redis-the-hard-way-in-production/
Editor's Notes
- #8: Caching like memcached, persistence like MongoDB