@SuppressWarnings("ConstantConditions")
JavaDStream<WindowedValue<T>> getDStream() {
if (dStream == null) {
WindowedValue.ValueOnlyWindowedValueCoder<T> windowCoder =
WindowedValue.getValueOnlyCoder(coder);
// create the DStream from queue
Queue<JavaRDD<WindowedValue<T>>> rddQueue = new LinkedBlockingQueue<>();
JavaRDD<WindowedValue<T>> lastRDD = null;
for (Iterable<T> v : values) {
Iterable<WindowedValue<T>> windowedValues =
Iterables.transform(v, WindowingHelpers.<T>windowValueFunction());
JavaRDD<WindowedValue<T>> rdd =
jssc.sc()
.parallelize(CoderHelpers.toByteArrays(windowedValues, windowCoder))
.map(CoderHelpers.fromByteFunction(windowCoder));
rddQueue.offer(rdd);
lastRDD = rdd;
}
// create DStream from queue, one at a time,
// with last as default in case batches repeat (graceful stops for example).
// if the stream is empty, avoid creating a default empty RDD.
// mainly for unit test so no reason to have this configurable.
dStream =
lastRDD != null
? jssc.queueStream(rddQueue, true, lastRDD)
: jssc.queueStream(rddQueue, true);
}
return dStream;
}
public static void main(String[] args) throws Exception {
if (args.length < 1) {
System.err.println("Usage: JavaQueueStream <master>");
System.exit(1);
}
StreamingExamples.setStreamingLogLevels();
// Create the context
JavaStreamingContext ssc =
new JavaStreamingContext(
args[0],
"QueueStream",
new Duration(1000),
System.getenv("SPARK_HOME"),
JavaStreamingContext.jarOfClass(JavaQueueStream.class));
// Create the queue through which RDDs can be pushed to
// a QueueInputDStream
Queue<JavaRDD<Integer>> rddQueue = new LinkedList<JavaRDD<Integer>>();
// Create and push some RDDs into the queue
List<Integer> list = Lists.newArrayList();
for (int i = 0; i < 1000; i++) {
list.add(i);
}
for (int i = 0; i < 30; i++) {
rddQueue.add(ssc.sparkContext().parallelize(list));
}
// Create the QueueInputDStream and use it do some processing
JavaDStream<Integer> inputStream = ssc.queueStream(rddQueue);
JavaPairDStream<Integer, Integer> mappedStream =
inputStream.mapToPair(
new PairFunction<Integer, Integer, Integer>() {
@Override
public Tuple2<Integer, Integer> call(Integer i) {
return new Tuple2<Integer, Integer>(i % 10, 1);
}
});
JavaPairDStream<Integer, Integer> reducedStream =
mappedStream.reduceByKey(
new Function2<Integer, Integer, Integer>() {
@Override
public Integer call(Integer i1, Integer i2) {
return i1 + i2;
}
});
reducedStream.print();
ssc.start();
ssc.awaitTermination();
}