Redis is an open source, in-memory data structure storage system that can be used as: database, cache, and messaging middleware.

Spring Data Redis Documentation

• Redis is powerful open source , noSql , inMemory Database.
• Store Data in key-value format
• Master Slave Replication
• Redis has Lua Scripting Language Support

Redis Usage In Web-Application

• User Session Management
• Caching
• Pub/Sub [ Queues & Notification ]
• LeaderBoard For Gaming App
• GeoSpatial

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ACID

Vertical Scaling vs Horizontal Scaling

Sql Vs NoSql

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Installing Redis on Widnows

• Redis Project Doesn't officially Support windows, however microsoft integrated give alternative
• Click Here to download Redis for windows
• Extract Zip File And Execute redis-server and redis-cli
• For How to download Redis for Mac/Linux click here
• To Learn Redis Cloud Please click here and Register to get free redis cloud access
• To access redis using GUI tool click here

Redis Data Types To Know more click here to see documentation

Redis Commands Click Here and Select Group to know all available command and there description

• Command to Get All the Keys using patterns

• to update key Only if key exist use additional parameter XX

• to add key Only if key does not exist use additional parameter NX

• TTL is used to specify time to live

• Exist command is used to see if key exists or not

• OtherCommands [append , strlen , incr , incrby , decr , decrby , mget , mset ]

• List Other Commands [ lrange , rpop , lpop , lpush ]

Set

127.0.0.1:6379> sadd email e1 e2 e3 e4 e1
(integer) 4
127.0.0.1:6379> smembers email
1) "e2"
2) "e1"
3) "e4"
4) "e3"
127.0.0.1:6379> scard email
(integer) 4
127.0.0.1:6379> sadd newEmail e4 e5 e6
(integer) 3
127.0.0.1:6379> sdiff email newEmail
1) "e1"
2) "e2"
3) "e3"
127.0.0.1:6379> sunion email newEmail
1) "e2"
2) "e4"
3) "e3"
4) "e6"
5) "e5"
6) "e1"
127.0.0.1:6379> sinter email newEmail
1) "e4"

Ordered Set

127.0.0.1:6379> zadd num 1 2 5 6 7 9 4 0
(integer) 4
127.0.0.1:6379> zadd randTest 1 abc 2 pqr 1 abd 14 zzz
(integer) 4
127.0.0.1:6379> zrange num 0 1
1) "2"
2) "0"
127.0.0.1:6379> zrange num 0 -1
1) "2"
2) "0"
3) "6"
4) "9"
127.0.0.1:6379> zrange randTest 0 -1
1) "abc"
2) "abd"
3) "pqr"
4) "zzz"
127.0.0.1:6379> zadd randTest 1 klm
(integer) 1
127.0.0.1:6379> zrange randTest 0 -1
1) "abc"
2) "abd"
3) "klm"
4) "pqr"
5) "zzz"
127.0.0.1:6379> zcount randTest -inf +inf
(integer) 5
127.0.0.1:6379> zrank randTest klm
(integer) 2
127.0.0.1:6379> zscore randTest klm
"1"
127.0.0.1:6379> zadd test abc abc pqr pqr klm klm
(error) ERR value is not a valid float

Hash

127.0.0.1:6379> hset student name zuned
(integer) 1
127.0.0.1:6379> hget student name
"zuned"
127.0.0.1:6379> hmset student name zuned gender male grade A
OK
127.0.0.1:6379> hmget student name gender and grade
1) "zuned"
2) "male"
3) (nil)
4) "A"
127.0.0.1:6379> hgetall student
1) "name"
2) "zuned"
3) "gender"
4) "male"
5) "grade"
6) "A"
127.0.0.1:6379> hexists student name
(integer) 1
127.0.0.1:6379> hkeys student
1) "name"
2) "gender"
3) "grade"
127.0.0.1:6379> hvals student
1) "zuned"
2) "male"
3) "A"
127.0.0.1:6379> hdel student grade
(integer) 1
127.0.0.1:6379> hlen student
(integer) 2
127.0.0.1:6379>

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Redis Persistence

1. RDB (Redis Database File) - make the snapshot of data with a specific time interval [redis fork child process which then makes the temporary RDB file, once the child process finishes the writing process, it replace the new file]
2. AOF (Append Only File) - Logs Each Write Operation receive by the server
3. Hybrid (RDB & AOF)

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Redis Back command -> save [ this will create dump file]

Redis Sentinal -> The primary purpose of sentinel is High Availability by providing Monitoring / Notifying / Instance Failover.

• On Master Failure, Sentinel promotes one of the slaves to the master then make the additional slave.
• Sentinel Act as a source of Authority for clients. Clients connect with sentinel to ask the address of the current master
• Redis Sentinel is the specific execution mode of the Redis server
• Redis Client must have sentinel support

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Redis Cluster: is data sharding solution which automatically manages failover and replication

• Data Sharding is the method to break up Big Database(DB) into the many smaller parts. It is done for Manageability, Availability, Performance, and load balancing of application.
• The reason for Data Sharding is that, After a certain point, it is cheaper and more attainable to scale horizontally by adding more machines than to grow vertically.

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Redis Transaction allows multiple query executed in single transaction.

Redis Pub/Sub

Subscriber 1 - with pattern

127.0.0.1:6379> psubscribe weath*
Reading messages... (press Ctrl-C to quit)
1) "psubscribe"
2) "weath*"
3) (integer) 1
1) "pmessage"
2) "weath*"
3) "weather"
4) "Welcome to Weather Channel"

Subscriber 2

127.0.0.1:6379> subscribe weather
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "weather"
3) (integer) 1
1) "message"
2) "weather"
3) "Welcome to Weather Channel"

Publisher

127.0.0.1:6379> publish weather "Welcome to Weather Channel"

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Preffered Redis Java Client

• Jedis: small lightweight extremely fast client library for redis java
• Lettuce: Advanced Redis client for thread-safe sync, async, and reactive usage. Supports Cluster, Sentinel, Pipelining, and codecs
• Redission: distributed and scalable Java data structures on top of Redis server

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• To Monitor redis cache open terminal with redis-cli and type Monitor , it will start monitoring the cache

Important Cachce Topics

• what is the two-eighth law?
• what is hot data and cold data?
• cache avalanche
• cache penetration
• cache warming
• cache update
• cache downgrade

how to check memory Consumed by key

localhost:6379> MEMORY USAGE ECA
(integer) 48955
localhost:6379> MEMORY USAGE EXCHANGE_CONFIG_ATTR
(integer) 46911

how to clear all cache

localhost:6379> fushall