Resilient System Design

1. Introduction

Resilient system design focuses on creating systems that can handle failures and continue to operate effectively. This lesson covers essential concepts, design principles, and best practices to ensure software architecture remains robust under various conditions.

2. Key Concepts

3. Design Principles

1. Design for Failure: Assume components will fail and implement strategies to handle failures gracefully.
2. Implement Redundancy: Use duplicate components to provide fallback options in case of failure.
3. Decouple Components: Minimize dependencies between components to reduce the impact of failure.
4. Monitor and Alert: Continuously monitor system health and alert operators when issues arise.
5. Automate Recovery: Use automation to recover from failures whenever possible.

4. Best Practices

• Conduct regular chaos engineering experiments to test system resilience.
• Use health checks and circuit breakers to manage service dependencies.
• Implement graceful degradation strategies to maintain user experience during failures.

5. Code Examples

Here’s a simple example of a circuit breaker pattern using Python:

class CircuitBreaker:
    def __init__(self, failure_threshold, recovery_timeout):
        self.failure_threshold = failure_threshold
        self.recovery_timeout = recovery_timeout
        self.failure_count = 0
        self.last_failure_time = None
        self.state = "CLOSED"

    def call(self, func, *args, **kwargs):
        if self.state == "OPEN":
            if self.last_failure_time and (time.time() - self.last_failure_time) > self.recovery_timeout:
                self.state = "HALF_OPEN"
            else:
                raise Exception("Circuit is OPEN")

        try:
            result = func(*args, **kwargs)
            self.failure_count = 0
            self.state = "CLOSED"
            return result
        except Exception as e:
            self.failure_count += 1
            self.last_failure_time = time.time()
            if self.failure_count >= self.failure_threshold:
                self.state = "OPEN"
            raise e
                

6. FAQ