Redis is one of the fastest DB because it does all execution via in-memory.

• Mac

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

starting redis server

redis-server [path:config_file]

stopping redis server

redis-cli

shutdown

This is used to evaluate the performance of redis.

redis-benchmark

• -h : host ip address
• -p : host port
• -n : number of request
• -d : payload size (in bytes)
• -t : type of operation

redis-benchmark -h 127.0.01 -p 6370 -n 1000 -d 10 -t get set

String are basic operation used to write and read from redis.

• set [key] [value] : sets a value to the key
• get [key] : get the value for the key
• del [key] : deletes the key.
• expire [key] PX|EX : auto expire the keys
• persist [key] : stop key from auto expire
• mset [key] [value] ... [key] [value] : sets multiple keys and values
• mget [key] ... [key] : gets values from multiple keys
• exist [key] : check if the given key exist or not 1 -] yes 0 -] No
• incr [key] : increments value associated with the key by 1

List is used to store multiple values for a single key.

• lpush [key] [value] ... [value] : sets values for the key from the left of the list.
• rpush [key] [value] ... [value] : sets values for the key from the right of the list.
• lrange [key] [start] [end] : get values from the key by the start and end index. (Note : -1 is used to indicate the end of the list)
• llen [key] : get the length of the list.
• lpop [key] : remove the first elemet from the list at the left.
• rpop [key] : remove the first element from the list at the right.
• ltrim [key] [start] [end] : remove all the values except the range specified in the list.

A Hashes is a group of keys & values.

• hset [key] [field] [value] : stores a field and value to the key.
• hget [key] [field] [field] : gets the values for the field from the key.
• hmset [key] [field] [value] ... [field] [value] : stores multiple field and value to the key.
• hmget [key] [field] [value] ... [field] [value] : get multiple field and value from the key.

Set is also a list with difference in unique value persistence.

• sadd [key] [value] : adds values to the set.
• smembers [key] : gets values from the set.
• sismember [key] [value] : check if the member exist in set.
• scard [key] : get the total number.
• sdiff [set1] [set2] : list the diffference between the sets.
• sdiffstore [setA] [set1] [set2] : store the difference between set1 and set2 inside setA.
• spop [key] : remove the element from the set.
• srem [key] [obj] : remove the value from the set.

Redis transaction offer ACID property of a database.

• Multi : starts a transaction
• Exec : executes a transaction
• Discard : discard the existing transcation
• Watch : watch a variable , if the variable encounters a change then the redis transaction will fail.
• Unwatch : unwatch will remvoe the watch operation of the variable.

create a file with all the set operation ex : data.txt

cat <file-name.txt> | redis-cli --pipe

Redis data are store in-memory , meaning if the redis process is killed then the data is lost.

Redis offers 2 ways of data persistance.

• RBD - Redis Data Backup.
• AOF - Append only file.

RDB creates a data dump based on the condition and when the redis server is restarted the data dump is reloaded into the redis memory , therefore offering data persistance.

1.  Open ~/.redis_config
2.  provide the details on the directory / dump name 
3.  Use : save <seconds> <no of changes>

Based on the details provided above the dump file is created.

AOF creates a file that has all the commands executed on the redis server, when restarted redis re-executes all the command, therefore offering data persistance.

1.  Open ~/.redis_config
2.  provide the details on the directory
3.  enable:  appendonly -   yes
4.  provide the aof file name : appendfileName.aof
5.  provide the frequency of the persistance : appendfsync - always / second

Redis Replication is a master slave redis server configuration , that allows Read/write to master and only read from slave.

1.  Open ~/.redis_config of the slave redis server
2.  provide the master ipaddress:port in the replicaof field.

Refer to image for info.

In a master - slave config , if the master goes down then the entire application is halted. Redis Sentinal automatically handle the master down time by auto- enabling a slave as master.

Is a group of redis-server , seggrated as master and slave (ie) each master in the cluster will have a slave.

The total number of hashes allowed is 16K and it is evenly distributed across master.

if the master goes down in the cluster then the slave connected to the master will become the next master.

1. create 6 instace of redis server with some config values copied from ipanther repo .
2. start all 6 instance using redis server <config>
3. redis-cli --cluster create <ip address> <ip address> <ip address> <ip address> <ip address>  

• Quoram : is the min number of nodes to be avaiable before making a slave to master used in redis sentinal.

• slaveof : used in real time to point a slave to a different master.