Resiliency Paterns

 

Resiliency Patterns in Microservices

Resiliency patterns help microservices remain reliable and available even when failures occur. These patterns ensure that a system can handle faults gracefully, preventing cascading failures and improving user experience.

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1. Circuit Breaker Pattern

When to Use?

• When a service call is failing repeatedly.
• When a dependent service is slow or unresponsive.
• To prevent excessive retries that can overload the system.

Why Use It?

• Prevents system overload by stopping calls to a failing service.
• Helps recover gracefully by allowing time for the failed service to restart.

Example:

• A payment service in an e-commerce system relies on a third-party payment gateway.
• If the gateway is down, the Circuit Breaker trips and blocks further requests, preventing unnecessary failures.
• Once the gateway recovers, the Circuit Breaker resets and allows requests again.

Tools: Netflix Hystrix, Resilience4j

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2. Retry Pattern

When to Use?

• When temporary failures occur due to network issues or rate limits.
• When the failure is intermittent and expected to recover soon.

Why Use It?

• Automatically retries failed operations instead of failing immediately.
• Reduces temporary errors from affecting the user experience.

Example:

• A weather app makes API calls to a weather provider.
• If a request fails due to network timeout, it retries after a short delay before showing an error to the user.

Tools: Spring Retry, Polly (.NET), Resilience4j

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3. Bulkhead Pattern

When to Use?

• When different services or operations should be isolated to prevent cascading failures.
• When multiple components share resources like threads or database connections.

Why Use It?

• Prevents one failing service from taking down the entire system.
• Ensures that critical services continue running even if non-critical ones fail.

Example:

• A food delivery app has:
  • Order Service
  • Restaurant Search Service
  • User Profile Service
• If Restaurant Search is overwhelmed with requests, Bulkhead ensures it doesn’t consume all resources, keeping Order Processing unaffected.

Tools: Netflix Hystrix, Istio Service Mesh

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4. Fallback Pattern

When to Use?

• When a dependent service is unavailable, but a default response can be provided.
• When some functionality is better than complete failure.

Why Use It?

• Improves user experience by providing a degraded but usable service.
• Helps maintain system functionality during failures.

Example:

• A flight booking system calls an external Seat Availability API.
• If the API is down, a fallback response shows “Availability data is currently unavailable, please try again later” instead of an error.

Tools: Resilience4j, Spring Cloud Hystrix

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5. Timeouts Pattern

When to Use?

• When calling a service that may respond slowly.
• When preventing a request from hanging indefinitely.

Why Use It?

• Ensures slow services don’t block system resources.
• Prevents user frustration due to long waits.

Example:

• A banking app requests a user's transaction history.
• If the request takes longer than 3 seconds, it times out and returns a default response to avoid locking the user interface.

Tools: Spring Boot, Netflix Ribbon

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6. Rate Limiting Pattern

When to Use?

• When preventing excessive API requests from overloading services.
• When managing quota-based API consumption.

Why Use It?

• Protects services from DDoS attacks and spikes in traffic.
• Ensures fair usage across clients.

Example:

• A stock trading platform limits each user to 100 API calls per minute.
• If a user exceeds the limit, they receive an error message: "Rate limit exceeded, try again later."

Tools: Kong API Gateway, AWS API Gateway, Nginx

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7. Idempotency Pattern

When to Use?

• When ensuring duplicate requests don’t cause unintended effects.
• When dealing with financial transactions or order processing.

Why Use It?

• Prevents accidental duplicate processing.
• Ensures consistency even if a request is retried due to failures.

Example:

• A payment service processes a request to charge $100.
• If a network issue causes the client to retry the request, the system checks if it was already processed to avoid charging twice.

Tools: Unique Request IDs, Idempotency Keys (Stripe, PayPal)

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8. Shadow Traffic Testing Pattern

When to Use?

• When testing a new service version without affecting real users.
• When ensuring a system can handle increased load before deployment.

Why Use It?

• Identifies potential failures before releasing changes.
• Helps validate resiliency under real traffic conditions.

Example:

• A ride-sharing app launches a new Matching Algorithm.
• It receives duplicate traffic alongside the existing system but doesn’t affect real users, allowing engineers to measure impact safely.

Tools: AWS Traffic Mirroring, Nginx Traffic Splitting

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Final Thoughts

Resiliency patterns help microservices handle failures effectively and maintain a seamless user experience. Here’s a quick summary of when to use each pattern:

By implementing these patterns, you can build a fault-tolerant, scalable, and robust microservices architecture.