Microservices architecture has become increasingly popular in the world of software development. It allows developers to build complex applications by breaking them down into smaller, independent services that are easier to manage and scale. However, as microservices communicate with each other over a network, they are prone to failures and errors. To handle these challenges, fault-tolerant measures need to be implemented.

In this blog post, we will explore how GlassFish and Eclipse MicroProfile Fault Tolerance can be used together to build robust and fault-tolerant microservices in Java.

What is Fault Tolerance?

Fault tolerance is the ability of a system to remain operational even when some of its components fail. In a microservices architecture, fault tolerance ensures that even if one service fails or encounters an error, the other services continue to provide their functionalities.

Introducing GlassFish

GlassFish is an open-source application server that supports Java Platform, Enterprise Edition (Java EE) applications. It provides a runtime environment for deploying and managing Java EE applications, including microservices. GlassFish has built-in features for high availability, scalability, and reliability, making it a suitable choice for building fault-tolerant microservices.

Eclipse MicroProfile Fault Tolerance

Eclipse MicroProfile Fault Tolerance is a set of annotations and APIs that enable developers to build fault-tolerant microservices easily. It provides mechanisms for handling and recovering from failures, including timeouts, retries, and circuit breakers.

Here are some important annotations provided by Eclipse MicroProfile Fault Tolerance:

• @Timeout: Specifies the maximum time a method should execute before timing out.
• @Retry: Defines the number of times a method should be retried in case of failure.
• @Fallback: Specifies an alternative method to be executed when the original method fails.
• @CircuitBreaker: Prevents calling a failed method for a specified period, instead, a fallback method is executed.
• @Bulkhead: Limits the number of simultaneous calls to a method.

Implementation Example

Let’s take a look at an example implementation of fault tolerance using GlassFish and Eclipse MicroProfile Fault Tolerance in Java.

import javax.inject.Inject;
import org.eclipse.microprofile.faulttolerance.Fallback;
import org.eclipse.microprofile.faulttolerance.Retry;
import org.eclipse.microprofile.faulttolerance.Timeout;

@ApplicationScoped
public class UserService {

    @Inject
    private UserDatabase userDatabase;

    @Timeout(3000)
    @Retry(maxRetries = 3)
    @Fallback(fallbackMethod = "getUserFromCache")
    public User getUser(String userId) {
        return userDatabase.getUser(userId);
    }

    public User getUserFromCache(String userId) {
        return Cache.getUser(userId);
    }
}

In the above example, we have a UserService class that retrieves user information from a UserDatabase. The getUser method uses fault tolerance annotations to handle failures gracefully. It specifies a timeout of 3000 milliseconds, retries the method up to 3 times in case of failure, and falls back to getUserFromCache method if all retries fail.

By leveraging these annotations, developers can easily add fault tolerance capabilities to their microservices.

Conclusion

Building fault-tolerant microservices is crucial for ensuring the reliability and stability of complex distributed systems. GlassFish provides a robust runtime environment for deploying Java EE applications, while Eclipse MicroProfile Fault Tolerance offers annotations and APIs for implementing fault tolerance in a straightforward manner.

By combining these technologies, developers can create resilient microservices that can handle failures gracefully and continue to provide essential functionalities.