Resilience is crucial for building reliable Spring applications that can withstand failures and unpredictable network conditions. In this chapter, you will explore how to combine a circuit breaker with a timeout to prevent cascading failures and improve application stability. You will learn the core principles behind these patterns, see how to configure them in a Spring context, and understand when to apply them to protect your services from slow or failing dependencies.

Combining Circuit Breakers with Timeouts in Spring

Circuit breakers and timeouts are two essential patterns for building resilient applications. When you combine them, you protect your system from both slow and failing services.

Circuit breakers watch for repeated failures in a remote call or dependency. If too many failures happen, the circuit breaker "opens" to stop further calls, allowing your system to recover instead of wasting resources.

Timeouts set a maximum wait time for an operation. If a call takes too long, the timeout triggers and stops the waiting, so your application does not get stuck.

When you use both together in a Spring application:

• The timeout ensures that calls do not hang indefinitely;
• The circuit breaker counts timeouts as failures, increasing its failure count;
• If too many timeouts or errors occur, the circuit breaker opens, quickly failing new requests instead of waiting for more timeouts;
• This combination keeps your application responsive and prevents cascading failures.

In Spring, you typically add a timeout to your service call (such as with @Timeout or a configuration property), and wrap the call with a circuit breaker (such as with @CircuitBreaker).

Example:

Suppose you call a payment service that sometimes responds slowly. You set a 2-second timeout for the call. If the payment service takes longer, the timeout triggers, and the circuit breaker counts this as a failure. After a few such failures, the circuit breaker opens, and your application quickly returns an error message instead of waiting for more timeouts.

This approach helps you deliver a better user experience and maintain system stability, even when dependencies are unreliable.

How Circuit Breaker and Timeout Work Together

The circuit breaker pattern prevents repeated failures by monitoring the success and failure of requests to a remote service. If failures exceed a defined threshold, the circuit "opens" and blocks further attempts, allowing the system to recover and avoid wasted resources.

A timeout defines the maximum duration you allow a remote call to take before considering it failed. If the call does not complete within the set time, the request is automatically marked as a failure.

When you combine a circuit breaker with a timeout:

• The timeout ensures that slow or unresponsive remote services do not hang your application;
• Each timeout-triggered failure is counted by the circuit breaker;
• If too many timeouts (or other failures) occur, the circuit breaker opens and blocks further calls for a defined period.

This combination protects your application from both persistent errors and slowdowns in dependent services.

Example Explanation

Suppose you wrap a remote call with both a circuit breaker and a timeout. When the remote service is available and responsive, requests pass through normally. If the service starts responding slowly or stops responding, the timeout will trigger, marking those requests as failures. As failures accumulate, the circuit breaker tracks them. Once the failure threshold is reached, the circuit breaker opens, and all further requests are immediately failed or redirected to a fallback, without even attempting the remote call. This prevents your application from waiting on slow services and avoids overwhelming the remote system with repeated failed requests.

By using both patterns together, you ensure that your application remains responsive and resilient, even when dependent services are unreliable or slow.