This document provides an overview of Redis, including its creation, features, and persistence methods. Redis is an open-source, in-memory key-value store that was created by Salvatore Sanfilippo to solve the problem of storing real-time page view data from multiple websites. It features different data types that can be stored as keys, master-slave replication for availability, and two persistence methods: RDB, which takes periodic snapshots of the dataset, and AOF, which logs all write operations to reconstruct the dataset from disk on startup.

1. REDIS OVERVIEW
Dinh Hoang Long
Framgia, Inc.

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Outline
● NoSQL and Redis
● The Creation of Redis
● Redis Features
● Redis Persistence

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NoSQL
● Non-relational
● Distributed
● Open-source
● Horizontally scalable

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Redis
Key Value Store NoSQL DBMS

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The Creation of Redis

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The Creation of Redis
The story of Salvatore Sanfilippo (antirez)
Creator of Redis

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Business
● Receiving a stream of page views from multiple websites.
● Storing the latest n page views for every site
● Show latest page views in real time to users
● Maintaining history

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Problem
With a peak load of a few thousand page views per second
● Whatever the database schema was
● Whatever trade-offs is
→ No way for storing by SQL

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The Creation of Redis
Solution
● In-memory data store
● Storing lists as a native data type
● Implementing using C language
● Adding fork-based persistence feature

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The Creation of Redis
Solution
● In-memory data store
● Storing lists as a native data type
● Implementing using C language
● Adding fork-based persistence feature
→ Finally, Redis was born!

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Redis Features
● Data Model
● Master/Slave Replication
● In-memory

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Data Model
● STRING

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Data Model
● STRING
● LIST

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Data Model
● STRING
● LIST
● SET

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Data Model
● STRING
● LIST
● SET
● HASH

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Data Model
● STRING
● LIST
● SET
● HASH
● ZSET (Sorted Set)

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Master/Slave Replication
Source: http://harish11g.blogspot.com

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In-memory
FAST

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What happened if server is turned off?

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Redis Persistence

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Redis Persistence
Storing data in hard disk
● RDB (Redis Database)
● AOF (Append Only File)

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RDB (Redis Database)

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RDB (Redis Database)
Point-in-time snapshots of dataset at specified intervals.

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RDB (Redis Database)
Advantages
● Perfect for backup and transfer
● Maximum performance
- Child process: Persist on disk
- Parent process: No I/O

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RDB (Redis Database)
Disadvantages
● Cannot minimize the chance of data loss
● fork() can be time consuming if the dataset is big

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AOF (Append Only File)

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AOF (Append Only File)
● Logs every write operation received by the server
● Plays again operation at server startup to reconstruct
the original dataset

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AOF (Append Only File)
Advantages
● Durability (sync every second, every query)
● No seek is required
● Automatically rewrite AOF in background when it
gets too big

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AOF (Append Only File)
Disadvantages
● Files are usually bigger than RDB files.
● Can be slower than RDB
● Rare bugs in specific commands

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What should we use?

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References
TỔNG QUAN VỀ REDIS http://tech.blog.framgia.com/vn/?p=3365
@dinhhoanglong91

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