Singleton pattern in LLD - Architecture Diagram

System Overview - Singleton pattern

The Singleton pattern ensures a class has only one instance and provides a global point of access to it. It is commonly used when exactly one object is needed to coordinate actions across the system, such as a configuration manager or a logging service.

Architecture Diagram

  +-------------------+
  |    Client Code    |
  +---------+---------+
            |
            v
  +-------------------+
  | Singleton Class   |
  |  (Single Instance)|
  +---------+---------+
            |
            v
  +-------------------+
  |  Shared Resource  |
  +-------------------+

Components

Client Code

client

Requests access to the singleton instance

Singleton Class

service

Ensures only one instance exists and provides global access

Shared Resource

resource

The resource or data managed by the singleton instance

Request Flow - 5 Hops

Client Code → Singleton Class

Singleton Class → Singleton Class

Singleton Class → Singleton Class

Singleton Class → Client Code

Client Code → Shared Resource

Failure Scenario

Component Fails:Singleton Class

Impact:If the singleton instance creation fails, clients cannot access the shared resource, causing system features relying on it to fail.

Mitigation:Implement error handling during instance creation and fallback mechanisms or retries to ensure instance availability.

Architecture Quiz - 3 Questions

What is the main purpose of the Singleton Class in this architecture?

A To ensure only one instance exists and provide global access

B To handle multiple client requests simultaneously

C To store user data temporarily

D To balance load between servers

Design Principle

The Singleton pattern centralizes control by restricting instantiation to one object, ensuring consistent access to shared resources and preventing conflicts from multiple instances.