This code snippet show how MongoDB Async driver can be used with RxJava

MongoExample.java

import java.util.concurrent.CountDownLatch;

import com.mongodb.CursorType;
import com.mongodb.async.client.MongoClients;
import com.mongodb.async.client.MongoCollection;
import com.mongodb.async.client.MongoDatabase;
import org.bson.Document;
import rx.Observable;

/**
 * This code snippet show how MongoDB Async driver can be used
 * with RxJava to consume a capped collection with Tailable cursor.
 * <p/>
 * Each time a document will be inserted into the collection,
 * you'll be notified.
 */
public class MongoExample {

    public static void main(String[] args) throws InterruptedException {

        CountDownLatch latch = new CountDownLatch(1);

        MongoDatabase db = MongoClients.create().getDatabase("test");
        MongoCollection<Document> collection = db.getCollection("helloworld");
        Observable.create(subscriber ->
                        collection.find()
                                .cursorType(CursorType.TailableAwait)
                                .forEach(subscriber::onNext, (aVoid, throwable) -> {
                                    if (throwable == null) {
                                        subscriber.onCompleted();
                                    } else {
                                        subscriber.onError(throwable);
                                    }
                                })
        ).subscribe(System.out::println, Throwable::printStackTrace, latch::countDown);

        latch.await();
        System.out.println("Completed");
    }
}