What Is Reactive?

1. Responsive

2. Resilient

3. Elastic

4. Message Driven

http://www.reactivemanifesto.org/

Responsive

1. Fast Failure

2. Reliable Timeouts

3. Builds Confidence

Resilient

1. Replication

2. Containment

3. Isolation

4. Recovery

5. Testing

Elastic

1. Sharding

2. Replication

3. Scaling

4. Monitoring

Message Driven

1. Location Transparency

2. Loose Coupling

3. Fault Isolation

4. Error Delegation

So, what is reactive?

"Reactive programming is programming with asynchronous data streams..." - André Staltz

https://gist.github.com/staltz/868e7e9bc2a7b8c1f754

Reactive Tools

For The JVM

RxJava

/*
 * Fetch a list of Wikipedia articles asynchronously, with error handling.
 */
def fetchWikipediaArticleAsynchronouslyWithErrorHandling(String... wikipediaArticleNames) {
    return Observable.create({ subscriber ->
        Thread.start {
            try {
                for (articleName in wikipediaArticleNames) {
                    if (true == subscriber.isUnsubscribed()) {
                        return;
                    }
                    subscriber.onNext(new URL("http://en.wikipedia.org/wiki/"+articleName).getText());
                }
                if (false == subscriber.isUnsubscribed()) {
                    subscriber.onCompleted();
                }
            } catch(Throwable t) {
                if (false == subscriber.isUnsubscribed()) {
                    subscriber.onError(t);
                }
            }
            return (subscriber);
        }
    });
}

Quasar

Vert.X

Akka/Play Framework

Which Is The Best?

That's up to you to decide...

The answer varies depending on the application and the team and the company you are working for!