Learn Redis - Top and Common Commands to Get Started

Key Redis Commands for New Users

Contents

1. About Redis

2. Set Up

3. Application

4. Access

5. User Management

6. Basic Operations

7. Data Operations

8. Maintenance

9. Advanced

10. Security

11. Monitoring and Performance

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About Redis

Overview 

• Redis is an open-source, in-memory data structure store 

• Used for multiple purposes, as 

  • A database

  • A cache

  • A message broker

• Known for its speed and flexibility

• Supports various data structures such as strings, hashes, lists, sets, and more

• Commonly used for caching, real-time analytics, session management, and message queuing

Key Features

• In-Memory Storage

  • Stores data in memory

  • Provides extremely fast read and write operations

• Data Structures

  • Supports a wide variety of data structures 

  • Includes - strings, hashes, lists, sets, sorted sets, bitmaps, hyperloglogs, geospatial indexes

• Persistence

  • Offers options for snapshotting (RDB) and append-only file (AOF) for data durability

• Replication

  • Supports master-slave replication for high availability and read scalability

• Transactions

  • Provides support for transactions with the ability to execute multiple commands atomically

• Pub/Sub Messaging

  • Built-in publish/subscribe messaging capabilities for real-time communication

Comparison to Alternatives

• MySQL

  • A traditional relational database better suited for structured data and complex queries

  • Redis is designed for high-speed, in-memory operations and is often used alongside relational databases for caching

• SQLite

  • Lightweight and serverless, ideal for embedded systems and small apps

  • Redis offers much faster performance and is used for different purposes such as caching and real-time data processing

• PostgreSQL

  • An advanced RDBMS with strong ACID compliance and support for complex queries

  • Redis is faster for in-memory operations and is often used for caching and real-time analytics, complementing relational databases.

• MongoDB

  • A NoSQL database designed for high flexibility and scalability with unstructured data

  • Redis excels in speed and is used for caching, real-time analytics, and session management, often alongside NoSQL databases for performance optimization

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Set-Up

Check Installation and Version

$ redis-server --version

Installation 

$ sudo apt update
$ sudo apt install redis-server

Uninstallation 

$ sudo apt remove redis-server
$ sudo apt autoremove

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Application 

Start-Up

$ sudo service redis-server start

Check Status

$ sudo service redis-server status

Check Port

$ sudo netstat -tuln | grep 6379

Power-Off

$ sudo service redis-server stop

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Access

Single Login into Database

$ redis-cli

Persist Login into Database

• Redis doesn't require persistent login management

• It simply uses simple authentication with a password set in the configuration file

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User Management

• Redis does not support creating users and managing privileges 

• Redis is simply designed to be a simple, key-value store database engine

• Access control is typically handled via configuration, through the /etc/redis/redis.conf

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Basic Operations

List Databases 

Redis has 16 databases by default, identified by numbers 0 to 15:

$ redis-cli INFO keyspace

Create Database

To create a database, with a database number from 0 to 15:

$ redis-cli

SELECT database_number

Example:

• Since Redis is a key-value store, we simulate the employee management database using hashes and sets

• In this example, we will create a database and connect to it

$ redis-cli

SELECT 0

Clear Database Data

Clear all the data from a single database, the currently selected one:

$ redis-cli FLUSHDB

To delete all data from all databases:

$ redis-cli FLUSHALL

Delete Database

Redis databases are fixed - so you cannot delete them.

• However, you can clear them, as shown above

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Data Operations

Create Table

• Redis is a key-value store and does not support tables

• However, you can simulate tables using keys and values

Example:

Use a hash to store department information:

HSET dept:1 name "Finance"
HSET dept:2 name "Human Resources"
HSET dept:3 name "Marketing"

Example:

Use a hash to store employee information and a set for department membership:

HSET emp:1 name "John Doe" email "john.doe@example.com" dept_id 1
HSET emp:2 name "Jane Smith" email "jane.smith@example.com" dept_id 2
HSET emp:3 name "Michael Johnson" email "michael.johnson@example.com" dept_id 3

SADD dept:1:employees 1
SADD dept:2:employees 2
SADD dept:3:employees 3

Insert Data

To set a key-value pair:

$ SET key value

Example:

Add a new employee and assign to a department:

HSET emp:4 name "Emily Davis" email "emily.davis@example.com" dept_id 1
SADD dept:1:employees 4

Update Data

$ SET key new_value

Example:

Update an employee's email:

HSET emp:1 email "john.doe.new@example.com"

Delete Data

$ DEL key

Example:

Delete an employee and remove from the department set:

DEL emp:3
SREM dept:3:employees 3

Query Data

$ GET key

Example:

Retrieve all employees in a department:

SMEMBERS dept:1:employees

Example:

Get employee details:

HGETALL emp:1

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Maintenance

Backup Database

To create a backup of the Redis database, use the SAVE command:

• This performs a synchronous save of the dataset

$ redis-cli SAVE

Redis configuration and data files are stored in the following directories:

1. Configuration File (redis.conf):

   • Location: /etc/redis/redis.conf

   • This is the default location for the Redis configuration file in Ubuntu

2. Data Directory:

   • By default, Redis stores its data files, including a backup (example: dump.rdb) snapshot file, in a directory specified by the dir directive in the redis.conf file

   • If you haven't changed the default configuration, Redis stores data in /var/lib/redis/

   • The dump.rdb file, created when you issue a SAVE command, will be located in this directory

$ sudo ls/etc/redis

Output:

redis.conf

$ sudo nano /etc/redis/redis.conf
$ sudo ls /var/lib/redis

Output:

dumb.rdb

Restore Database

To restore a Redis database:

1. Copy the backup file (dump.rdb) to the Redis data directory 

   • Recall that from above, the data directory is specified in /var/lib/redis/ by default

2. Then, restart the Redis service

$ cp backup.rdb /var/lib/redis/dump.rdb
$ sudo service redis-server restart

Optimize Database

Redis automatically manages memory efficiently, but you can use the MEMORY command to get insights

Check Logs

Redis logs are typically located in /var/log/redis/

You can view them using:

$ tail -f /var/log/redis/redis-server.log

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