Example of a Circuit Breaker implementation in Java using the Hystrix library

Category : Microservices | Sub Category : Microservices | By Prasad Bonam Last updated: 2023-07-15 14:56:49 Viewed : 360

Example of a Circuit Breaker implementation in Java using the Hystrix library:

Here is an example of a Circuit Breaker implementation in Java using the Hystrix library:

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import com.netflix.hystrix.HystrixCommand;
import com.netflix.hystrix.HystrixCommandGroupKey;
import com.netflix.hystrix.HystrixCommandKey;
import com.netflix.hystrix.HystrixCommandProperties;

public class MyServiceCommand extends HystrixCommand<String> {
    private final String fallbackResponse = "Fallback response";

    public MyServiceCommand() {
        super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("MyServiceGroup"))
                .andCommandKey(HystrixCommandKey.Factory.asKey("MyServiceCommand"))
                .andCommandPropertiesDefaults(HystrixCommandProperties.Setter()
                        .withCircuitBreakerEnabled(true)
                        .withCircuitBreakerErrorThresholdPercentage(50)
                        .withCircuitBreakerRequestVolumeThreshold(10)
                        .withCircuitBreakerSleepWindowInMilliseconds(5000)));
    }

    @Override
    protected String run() throws Exception {
        // Call the external service or perform the desired operation
        // Return the result if successful
        return "Service response";
    }

    @Override
    protected String getFallback() {
        // Return a fallback response when the circuit is open or an error occurs
        return fallbackResponse;
    }
}

In this example, we create a class MyServiceCommand that extends HystrixCommand<String>, representing a command that calls an external service or performs some operation. The Hystrix annotations are used to configure the circuit breaker behavior.

In the constructor, we define the command and group keys, and set the command properties related to the circuit breaker, such as enabling it, setting the error threshold percentage, request volume threshold, and sleep window duration.

The run() method represents the actual operation that the command performs. You can place your service call or any other desired logic inside this method. If the operation is successful, the method should return the result.

The getFallback() method provides a fallback response that is returned when the circuit is open (i.e., the error threshold is exceeded) or when an exception occurs. The fallback response provides a graceful degradation of functionality.

To execute the command, you can create an instance of MyServiceCommand and call its execute() method:

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MyServiceCommand command = new MyServiceCommand();
String result = command.execute();This will execute the command and return the result, taking into account the circuit breaker behavior and fallback response.

Note that this example uses the Hystrix library, which is one of the popular implementations of the Circuit Breaker pattern in Java. There are other libraries available as well, such as resilience4j and Sentinel, each with its own API and configuration options.