A quick introduction to Redis

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Hello Redis! a quick introduction Thursday, June 20, 13

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Who is this guy? ‣Brad Montgomery @bkmontgomery on twitter ‣Organizer of MEMpy; www.mempy.org ‣Cofounder/Developer at Work for Pie; www.workforpie.com Thursday, June 20, 13

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Redis? Redis ("REmote DIctionary Server"), is an in-memory Key-Value Database. Also frequently called a "data structure server". Thursday, June 20, 13

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Redis? Redis ("REmote DIctionary Server"), is an in-memory Key-Value Database. Also frequently called a "data structure server". Thursday, June 20, 13

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Redis? Redis ("REmote DIctionary Server"), is an in-memory Key-Value Database. Also frequently called a "data structure server". Thursday, June 20, 13

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Key Points: ‣Very Fast (writes & reads) ‣It's Durable (it can be). ‣In-Memory. Your data should ﬁt in RAM. ‣Values are associated with unique Keys ‣Data Types: Strings, Lists, Sets, Sorted Sets, Hashes ‣Every command is Atomic ‣Keys can be segmented. Thursday, June 20, 13

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Can I use? Many “supported” language libraries: C, C#, Clojure, Dart, Erlang, Go, Haskell, Java, Lua, Node.js, Perl, PHP, Python, Ruby, Scala (many more “unsupported” libraries) See http://redis.io/clients for more info. Thursday, June 20, 13

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Durability Wait... Isn’t Redis an “in-memory” data store? ‣ RDB: Write Snapshots to disk; Based on number of changes in a keys in a time period; ‣ AOF: (append-only ﬁle) writes data to disk ‣ None: ONLY stores data in memory. ‣ Both: If you really care about your data, use AOF, with periodic snapshots. Thursday, June 20, 13

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On Keys ‣Redis is lumped into the NoSQL category... ‣You query data via a Key ‣You don’t query the values ‣Keys can be anything (including binary data) ‣Smaller keys are good. ‣Deﬁne a schema: object-type:id:field Thursday, June 20, 13

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On Values Values are associated with a unique key and are stored as adata type: ‣Strings ‣Lists ‣Sets ‣Sorted Sets ‣Hashes Thursday, June 20, 13

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Strings ‣Most basic data type: ‣Can store up to 512Mb ‣Examples: Serialized data such as JSON or binary data such as a JPEG image. ‣Redis doesn't care what you store. Thursday, June 20, 13

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Strings Set some values: SET users:brad "{email: [email protected], password: SOMEHASH}" SET users:brad:avatar "\xf8\xf8\xf8\xf0\xf0\xf0\xf8\xf8\xf8\xeb..." Get some values: GET users:brad GET users:brad:avatar Thursday, June 20, 13

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Strings Incrementing: SET users:count 0 INCR users:count # users:count -> 1 INCRBY users:count 5 # users:count -> 6 Additional Utilities: STRLEN users:brad # returns 53 APPEND users:brad " moar data" # Careful! GET users:brad # Returns: "{email: [email protected], password: SOMEHASH} moar data" Thursday, June 20, 13

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Lists ‣Store & Manipulate a list (or array) ‣Maintains Order ‣Fast index-based operations Thursday, June 20, 13

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Lists Adding to a list: LPUSH users sally LPUSH users jane LPUSH users bill Do an index-based lookup: LINDEX users 0 # Returns "bill" LINDEX users 2 # Returns "sally" Thursday, June 20, 13

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Lists Access a range of items: LRANGE users 0 3 # returns "bill", "jane", "sally" Utilities: LLEN users # returns 3 LSET users 0 sallie # changes "sally" to "sallie" POP items (removes ﬁrst item pushed): LPOP users # returns "bill" Thursday, June 20, 13

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Sets ‣Stores unique values ‣No Order ‣Set-based Operations ‣Great for “tagging” or tracking properties Thursday, June 20, 13

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Sets Adding a set: SADD blog:10 redis nosql SADD blog:11 couchdb nosql Updating a Set: SADD blog:11 json # would now include "couchdb", "nosql", "json" Remove an item from a set: SREM blog:11 json # removes the "json" value from the set tags for a blog entry. Thursday, June 20, 13

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Sets View the members of a set: SMEMBERS blog:10 # returns "nosql", "redis" Does an set contain a given value?: SISMEMBER blog:10 python # returns 0 or 1 Set-based operations: SUNION blog:10 blog:11 # returns "redis", "couchdb", "nosql" SINTER blog:10 blog:11 # returns "nosql" SDIFF blog:10 blog:11 # returns "redis" (in blog:10 but not blog:11) Thursday, June 20, 13

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Sorted Sets ‣Just like Sets, but each item gets a Score ‣Creates an Order or Ranking ‣Leaderboards! Thursday, June 20, 13

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Sorted Sets Add some users to the leaderboard: ZADD leaders 30 sally ZADD leaders 50 julie ZADD leaders 10 bill Find a rank (default ordering is low to high): ZRANK leaders bill # returns 0 Find a rank (sorted high to low): ZREVRANK leaders bill # returns 2 Thursday, June 20, 13

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Sorted Sets How many users have a score between 20 and 50 (inclusive): ZCOUNT leaders 20 50 # returns 2 Find a user's score: ZSCORE leaders bill # returns 10 Thursday, June 20, 13

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Hashes ‣Similar to strings, but with ﬁelds ‣Gives you well-deﬁned objects ‣Gives you Granular access ‣Think JSON or Python dictionaries Thursday, June 20, 13

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Hashes Given the JSON object for a user: { id: 1234, username: johndoe, email: [email protected], fullname: 'John Doe' } Store in a Redis HASH with: HSET users:1234 username johndoe HSET users:1234 email [email protected] HSET users:1234 fullname "John Doe" Thursday, June 20, 13

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Hashes Get individual ﬁeld values: HGET users:1234 username # returns "johndoe" Get Multiple ﬁeld values: HMGET users:1234 username email # returns "johndoe", "[email protected]" Get all keys/values for a hashed item: HGETALL users:1234 # returns: "username", "johndoe", # "email", "[email protected]", # "fullname", "John Doe" Thursday, June 20, 13

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Hashes Additional Utilities: HKEYS users:1234 # returns "username", "email", "fullname" HLEN users:1234 # returns 3 HEXISTS users:1234 password # returns 0 (false) HDEL users:1234 fullname # removes the "fullname" field & value Thursday, June 20, 13

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How is Redis Used? ‣High-frequency writes/reads (Metrics) ‣As a cache or storage for ephemeral data ‣Task Queue ‣Pub/Sup Thursday, June 20, 13

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Metrics Python Code: metric('github-api') Redis Keys are stored as: m:github-api:2013-01-31 -> 100 ; daily usage m:github-api:w:2013-05 -> 1000 ; weekly usage m:github-api:m:2013-01 -> 10,000 ; monthly usage m:github-api:y:2013 -> 100,000 ; yearly usage ‣django-redis-metrics ‣Easy, Arbitrary metrics for Django apps ‣Backed by Redis Thursday, June 20, 13

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Metrics daily queries to the github Thursday, June 20, 13

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Cache/Ephemeral Store ‣User Session Keys ‣“ﬂash messages” ‣cache for common database query results Redis Key expiration EXPIRE messages:brad 30 # expires the "messages:brad" key in 30s Thursday, June 20, 13

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Task Queue ‣Simple, [asynchronous] Task Queue ‣We use python-rq (e.g. hit 3rd-party REST api’s during an http request). Thursday, June 20, 13

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Pub/Sup ‣Implements the Publish-Subscribe Pattern ‣Subscribe to a channel ‣Publish a message on a Channel ‣Subscribers get the message. Subscribe to a Channel called messages: SUBSCRIBE messages Publish a message: PUBLISH messages "Hello World!" Thursday, June 20, 13

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There’s More! Thursday, June 20, 13

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There’s More! but we’re out of time! Thursday, June 20, 13

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Thanks! Learn more here: ‣Ofﬁcial Docs: redis.io ‣Try it Online: try.redis-db.com ‣The Little Book of Redis Thursday, June 20, 13