Question

You are responsible for the design of a communications switch that has to provide \(24 / 7\) availability but that is not safety-critical. Giving reasons for your answer, suggest an architectural style that might be used for this system.

Short answer

Event-Driven Architecture is suggested for its scalability and redundancy capabilities, ensuring 24/7 availability.

Step-by-step solution

Understand the Requirements

The system must provide 24/7 availability, which means it must be highly reliable and have minimal downtime. However, it is not safety-critical, so extreme measures for fault tolerance may not be necessary.

Analyze Architectural Styles

Review various architectural styles to see how they can meet the requirement of high availability. Some common styles include Layered Architecture, Microservices, Client-Server, and Event-Driven Architecture.

Evaluate High Availability Considerations

For 24/7 availability, consider redundancy, fault tolerance, and load balancing. Architectures supporting these features are preferable for ensuring uninterrupted service.

Suggest Event-Driven Architecture

Event-Driven Architecture is suitable as it offers scalability, loose coupling, and can easily integrate with redundant systems to ensure high availability. Events can trigger responses without the need for a consistent synchronous operation, which can help in efficiently managing failures.

Justify the Choice

Event-Driven Architecture allows independent processing of requests and can handle traffic spikes through decoupling. Its ability to handle components separately means failure in one part doesn't necessarily compromise the entire system.

Key concepts

High Availability

High availability is a crucial aspect of system architecture design, especially when 24/7 uptime is required. This concept ensures that systems are operational and accessible almost all of the time, with minimal downtime.

It involves designing systems to automatically recover from failures, minimizing the impact on users. High availability is achieved through measures such as:

• Redundancy: Having backup components that can take over in case of failure.
• Load balancing: Distributing network or application traffic across multiple servers.
• Failover: Switching to a standby resource when the primary resource fails.

These techniques ensure that users experience minimal service interruptions, even when some components fail.

Event-Driven Architecture

Event-Driven Architecture is a paradigm where actions in the system trigger events and subsequent processes. This style is well-suited to applications that need to respond quickly and efficiently to changing circumstances, making it ideal for high availability systems.

Here are some of the key features:

• Loose Coupling: Components within the system do not depend heavily on each other, allowing for isolated failures.
• Scalability: It can easily accommodate additional resources to handle increased load and traffic spikes.
• Asynchronous Processing: Events are processed independently, reducing bottlenecks and improving system resilience.

With Event-Driven Architecture, systems can react to events in real-time, maintaining performance and availability across disparate components.

Redundancy

Redundancy in system architecture refers to the duplication of critical components or functions of a system to increase reliability. Redundant systems can seamlessly take over in case of failure, ensuring uninterrupted service.

The benefits of redundancy include:

• Increased Reliability: By having backups, systems can maintain function even if one component fails.
• Fault Isolation: Issues can be contained to specific areas without affecting the overall system.
• Operational Continuity: Users experience seamless service due to immediate failover.

Implementing redundancy in system architecture is a key strategy for achieving high availability and managing unexpected downtime effectively.

Fault Tolerance

Fault tolerance is the ability of a system to continue operating properly in the event of a component failure. This concept is critical for systems that need to offer constant availability and reliability.

Fault tolerance is achieved through strategies such as:

• Error Detection: Identifying and isolating faults before they cause significant disruption.
• Graceful Degradation: Allowing systems to maintain functionality even at reduced capacity.
• Redundancy and Backups: Sharing the workload with secondary systems or redundant components when failures occur.

By incorporating fault tolerance into the design, systems can mitigate the impact of disruptions and maintain high levels of availability and user satisfaction.