9th July 2015

An introduction to Redisby Romain Francez

9th July 2015

Redis

“An in memory non relational database”

“Memcached but better”

“A data structure server”

9th July 2015

Redis is Simple

● Works out of the box○ No schema○ No user○ Default config works just fine

9th July 2015

Redis is Simple

● Key/Value Store

● Simple operations○ Usually get/set with variations

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Redis is Flexible

● Data types○ Bitmaps○ Hashes○ HyperLogLogs

■ Probabilistic data structure to estimate the cardinality of a set■ Memory efficient

○ Keys■ Yes, also a type■ Anything binary safe (like the content of an image)

○ Lists○ Sets○ Sorted Sets○ Strings

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Redis is Flexible

● Configuration○ Store denormalised data you can afford to lose?

■ By default in memory + snapshot on the disk■ Disable the disk writes

○ Use it as a cache?■ Use a LRU (Least Recently Used) memory policy

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Redis is Flexible

● Custom functions with lua● Transactions

○ If you need them

● Pub/Sub○ Isn’t even related to the key space

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Redis is Scalable

● High Availability with Sentinel○ Configuration based

● Most operations are O(1)○ But some have high constant time (See some Hyperloglogs commands)

● Non relational database○ No problems related to scaling relations across servers

● Partitioning○ With limitations

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Redis Use Cases

“So basically I can do everything and anything with Redis?”

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Widely adopted

● GitHub○ Routing, queue, config management

● Instagram○ Mapping photos with the user that created them○ Needs the persistence of data on disk○ Advanced usage of hashes

● StackOverflow○ Cache

● Twitter○ Timeline (tweets ordered by ids), ads○ On disk features not used○ Added custom data types

● Your favorite video site○ Hint: not YouTube○ Sorted sets and hashes○ Kept MySQL, but no reads from it: use it to populate Redis

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Other Usages

● Autocomplete● Search engine● Distributed locking● Session management● Leaderboards

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Leaderboard Example> ZADD leaderboard 13 "Cold" 22 "Cindy" 7 "mymo" 20 "herrrox" 15

"Dreaty" 4 "cqnqr"

(integer) 6

> ZREVRANGE leaderboard 0 2 WITHSCORES

1) "Cindy"

2) "22"

3) "herrrox"

4) "20"

5) "Dreaty"

6) "15"

> ZRANGE leaderboard 0 0 WITHSCORES

1) "cqnqr"

2) "4"

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Leaderboard Example> ZINCRBY leaderboard 20 "cqnqr"

"24"

> ZREVRANK leaderboard "cqnqr"

(integer) 0

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Leaderboard Example> ZCARD leaderboard

(integer) 6

> ZADD leaderboard 7 "BaDy"

(integer) 1

> ZCARD leaderboard

(integer) 7

> ZREM leaderboard "mymo"

(integer) 1

> ZCARD leaderboard

(integer) 6

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Conclusion

● Redis can be used for any of your needs○ You might have to get into advanced stuff though

● Handles well lots of data

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Thanks

Any questions ?

9th July 2015

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