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Redis Architecture and How It Works

Authors
  • avatar
    Name
    Hieu Cao
    Twitter

Introduction

Redis is renowned for its blazing-fast performance and flexibility. This article delves into the architecture of Redis, explaining how it handles in-memory data and persists it to disk, enabling high availability and reliability.

Key Components of Redis Architecture

1. In-Memory Data Store

At its core, Redis stores data in memory, which makes it incredibly fast. By keeping all data in RAM, Redis can process millions of read/write operations per second, making it ideal for real-time applications.

2. Single-Threaded Event Loop

Redis operates on a single-threaded event loop, handling all operations sequentially. While this might seem like a limitation, it eliminates the need for locking mechanisms, ensuring simplicity and speed.

3. Data Structures

Redis supports various data structures, including:

  • Strings
  • Hashes
  • Lists
  • Sets
  • Sorted Sets

These data types allow developers to solve complex problems with simple commands.

4. Persistence Options

Redis offers two primary methods to persist data to disk:

a) Snapshotting (RDB)

  • Creates point-in-time snapshots of the dataset.
  • Snapshots are saved as .rdb files.
  • Ideal for full backups at regular intervals.

b) Append-Only File (AOF)

  • Logs every write operation in a sequential file.
  • Provides more granular data durability.
  • Supports rewriting to optimize file size.

5. Replication

Redis supports master-slave replication:

  • Master: Handles all write operations.
  • Slave(s): Copy data from the master and serve read requests.
  • Replication enables high availability and load balancing.

6. Clustering

Redis clustering partitions data across multiple nodes:

  • Ensures horizontal scalability.
  • Allows Redis to handle large datasets.
  • Provides fault tolerance through data replication.

How Redis Processes Data

1. Command Execution

Redis follows a simple command-based interface. All commands are processed sequentially, ensuring predictable behavior.

Example:

SET user:1 "John"
GET user:1

2. Event Loop

The single-threaded event loop uses a multiplexing system to handle multiple connections efficiently.

3. Data Persistence Workflow

  • For RDB:
    1. Redis forks a child process.
    2. The child process writes data to a temporary file.
    3. The temporary file replaces the old snapshot.
  • For AOF:
    1. Commands are logged to the AOF file.
    2. Redis rewrites the file when it becomes too large.

Advantages of Redis Architecture

  1. Speed: In-memory storage and a single-threaded model make Redis extremely fast.
  2. Simplicity: The straightforward architecture ensures ease of use and maintenance.
  3. Flexibility: Rich data structures and persistence options cater to diverse use cases.
  4. Scalability: Replication and clustering enable Redis to scale horizontally.

Conclusion

Redis's architecture is a testament to its design principles of simplicity, speed, and reliability. By understanding how Redis processes data and persists it to disk, developers can harness its full potential to build high-performance applications.

Redis continues to be a go-to choice for developers seeking a fast, reliable, and versatile database solution.