Hystrix

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Example

Fallback Method: In Service B, the @HystrixCommand annotation is applied to the serviceB method. If the call to Service A fails or takes too long, Hystrix will invoke the fallbackServiceA method instead, returning a predefined response.

Service B

@GetMapping("/serviceB")
@HystrixCommand(fallbackMethod = "fallbackServiceA")
public String serviceB() {
    String response = restTemplate.getForObject("http://service-a/serviceA", String.class);
    return "Service B calls " + response;
}

public String fallbackServiceA() {
    return "Fallback response from Service B";
}

Service C

Fallback Method: In Service C, the @HystrixCommand annotation is used in a similar way. It wraps the call to Service B. If this call fails, Hystrix will call the fallbackServiceB method.

@GetMapping("/serviceC")
@HystrixCommand(fallbackMethod = "fallbackServiceB")
public String serviceC() {
    String response = restTemplate.getForObject("http://service-b/serviceB", String.class);
    return "Service C calls " + response;
}

public String fallbackServiceB() {
    return "Fallback response from Service C";
}

Summary of Hystrix Usage

Service B:

Primary Method: serviceB()
Fallback Method: fallbackServiceA()
If the call to Service A fails, the system falls back to returning "Fallback response from Service B".

Service C:

Primary Method: serviceC()
Fallback Method: fallbackServiceB()
If the call to Service B fails, the system falls back to returning "Fallback response from Service C".

Benefits of Using Hystrix

• Fault Isolation: If one service fails (like Service A), it does not affect the others (Service B and Service C).
• Fallback Mechanism: Provides an alternative response, which can improve user experience by avoiding failures.
• Prevent Cascading Failures: Helps prevent failures from propagating through the system, allowing the application to remain functional even when some services are down.