Accessing Cassandra from Spark in Java

public class JavaDemo implements Serializable {

    private transient SparkConf conf;

    private JavaDemo(SparkConf conf) {

        this.conf = conf;

    }

    private void run() {

        JavaSparkContext sc = new JavaSparkContext(conf);

        generateData(sc);

        compute(sc);

        showResults(sc);

        sc.stop();

    }

    private void generateData(JavaSparkContext sc) {

    }

    private void compute(JavaSparkContext sc) {

    }

    private void showResults(JavaSparkContext sc) {

    }

    public static void main(String[] args) {

        if (args.length != 2) {

            System.err.println("Syntax: com.datastax.spark.demo.JavaDemo <Spark Master URL> <Cassandra contact point>");

            System.exit(1);

        }

        SparkConf conf = new SparkConf();

        conf.setAppName("Java API demo");

        conf.setMaster(args[0]);

        conf.set("spark.cassandra.connection.host", args[1]);

        JavaDemo app = new JavaDemo(conf);

        app.run();

    }

}

CassandraConnector connector = CassandraConnector.apply(sc.getConf());

try (Session session = connector.openSession()) {

    session.execute("DROP KEYSPACE IF EXISTS java_api");

    session.execute("CREATE KEYSPACE java_api WITH replication = {'class': 'SimpleStrategy', 'replication_factor': 1}");

    session.execute("CREATE TABLE java_api.products (id INT PRIMARY KEY, name TEXT, parents LIST<INT>)");

    session.execute("CREATE TABLE java_api.sales (id UUID PRIMARY KEY, product INT, price DECIMAL)");

    session.execute("CREATE TABLE java_api.summaries (product INT PRIMARY KEY, summary DECIMAL)");

}

List<Product> products = Arrays.asList(

        new Product(0, "All products", Collections.<Integer>emptyList()),

        new Product(1, "Product A", Arrays.asList(0)),

        new Product(4, "Product A1", Arrays.asList(0, 1)),

        new Product(5, "Product A2", Arrays.asList(0, 1)),

        new Product(2, "Product B", Arrays.asList(0)),

        new Product(6, "Product B1", Arrays.asList(0, 2)),

        new Product(7, "Product B2", Arrays.asList(0, 2)),

        new Product(3, "Product C", Arrays.asList(0)),

        new Product(8, "Product C1", Arrays.asList(0, 3)),

        new Product(9, "Product C2", Arrays.asList(0, 3))

);

JavaRDD<Product> productsRDD = sc.parallelize(products);

javaFunctions(productsRDD, Product.class).saveToCassandra("java_api", "products");

import static com.datastax.spark.connector.CassandraJavaUtil.*;

JavaRDD<Sale> salesRDD = productsRDD.filter(new Function<Product, Boolean>() {

    @Override

    public Boolean call(Product product) throws Exception {

        return product.getParents().size() == 2;

    }

}).flatMap(new FlatMapFunction<Product, Sale>() {

    @Override

    public Iterable<Sale> call(Product product) throws Exception {

        Random random = new Random();

        List<Sale> sales = new ArrayList<>(1000);

        for (int i = 0; i < 1000; i++) {

            sales.add(new Sale(UUID.randomUUID(), product.getId(), BigDecimal.valueOf(random.nextDouble())));

        }

        return sales;

    }

});

javaFunctions(salesRDD, Sale.class).saveToCassandra("java_api", "sales");

JavaPairRDD<Integer, Product> productsRDD = javaFunctions(sc)

        .cassandraTable("java_api", "products", Product.class)

        .keyBy(new Function<Product, Integer>() {

            @Override

            public Integer call(Product product) throws Exception {

                return product.getId();

            }

        });

JavaPairRDD<Integer, Sale> salesRDD = javaFunctions(sc)

        .cassandraTable("java_api", "sales", Sale.class)

        .keyBy(new Function<Sale, Integer>() {

            @Override

            public Integer call(Sale sale) throws Exception {

                return sale.getProduct();

            }

        });

JavaPairRDD<Integer, Tuple2<Sale, Product>> joinedRDD = salesRDD.join(productsRDD);

JavaPairRDD<Integer, BigDecimal> allSalesRDD = joinedRDD.flatMap(new PairFlatMapFunction<Tuple2<Integer, Tuple2<Sale, Product>>, Integer, BigDecimal>() {

    @Override

    public Iterable<Tuple2<Integer, BigDecimal>> call(Tuple2<Integer, Tuple2<Sale, Product>> input) throws Exception {

        Tuple2<Sale, Product> saleWithProduct = input._2();

        List<Tuple2<Integer, BigDecimal>> allSales = new ArrayList<>(saleWithProduct._2().getParents().size() + 1);

        allSales.add(new Tuple2<>(saleWithProduct._1().getProduct(), saleWithProduct._1().getPrice()));

        for (Integer parentProduct : saleWithProduct._2().getParents()) {

            allSales.add(new Tuple2<>(parentProduct, saleWithProduct._1().getPrice()));

        }

        return allSales;

    }

});

JavaRDD<Summary> summariesRDD = allSalesRDD.reduceByKey(new Function2<BigDecimal, BigDecimal, BigDecimal>() {

    @Override

    public BigDecimal call(BigDecimal v1, BigDecimal v2) throws Exception {

        return v1.add(v2);

    }

}).map(new Function<Tuple2<Integer, BigDecimal>, Summary>() {

    @Override

    public Summary call(Tuple2<Integer, BigDecimal> input) throws Exception {

        return new Summary(input._1(), input._2());

    }

});

javaFunctions(summariesRDD, Summary.class).saveToCassandra("java_api", "summaries");

JavaPairRDD<Integer, Summary> summariesRdd = javaFunctions(sc)

        .cassandraTable("java_api", "summaries", Summary.class)

        .keyBy(new Function<Summary, Integer>() {

            @Override

            public Integer call(Summary summary) throws Exception {

                return summary.getProduct();

            }

        });

JavaPairRDD<Integer, Product> productsRdd = javaFunctions(sc)

        .cassandraTable("java_api", "products", Product.class)

        .keyBy(new Function<Product, Integer>() {

            @Override

            public Integer call(Product product) throws Exception {

                return product.getId();

            }

        });

List<Tuple2<Product, Optional<Summary>>> results = productsRdd.leftOuterJoin(summariesRdd).values().toArray();

for (Tuple2<Product, Optional<Summary>> result : results) {

    System.out.println(result);

}