Generic/Template Programming in Flink

Generic/Template Programming in Flink

SourceFunction<T>

@Public
public interface SourceFunction<T> extends Function, Serializable {

    void run(SourceContext<T> ctx) throws Exception;
    
    void cancel();

    @Public // Interface might be extended in the future with additional methods.
    interface SourceContext<T> {
        void collect(T element);
        
        @PublicEvolving
        void collectWithTimestamp(T element, long timestamp);
        
        @PublicEvolving
        void emitWatermark(Watermark mark);

        @PublicEvolving
        void markAsTemporarilyIdle();
        Object getCheckpointLock();
        void close();
    }
}

@Override
        public void run(SourceContext<Integer> ctx) throws Exception {
            while ((start < counter || counter == -1) && isRunning) {
                synchronized (ctx.getCheckpointLock()) {
                    ctx.collect(start);
                    ++start;

                    // loop back to 0
                    if (start == Integer.MAX_VALUE) {
                        start = 0;
                    }
                }
                Thread.sleep(10L);
            }
        }

AsyncFunction<IN, OUT>

@PublicEvolving
public interface AsyncFunction<IN, OUT> extends Function, Serializable {    
    void asyncInvoke(IN input, ResultFuture<OUT> resultFuture) throws Exception;    
    default void timeout(IN input, ResultFuture<OUT> resultFuture) throws Exception {
        resultFuture.completeExceptionally(
            new TimeoutException("Async function call has timed out."));
    }
}

@Override
        public void asyncInvoke(final Integer input, final ResultFuture<String> resultFuture) {
            executorService.submit(() -> {
                // wait for while to simulate async operation here
                long sleep = (long) (ThreadLocalRandom.current().nextFloat() * sleepFactor);
                try {
                    Thread.sleep(sleep);

                    if (ThreadLocalRandom.current().nextFloat() < failRatio) {
                        resultFuture.completeExceptionally(new Exception("wahahahaha..."));
                    } else {
                        resultFuture.complete(
                            Collections.singletonList("key-" + (input % 10)));
                    }
                } catch (InterruptedException e) {
                    resultFuture.complete(new ArrayList<>(0));
                }
            });
        }

public static <IN, OUT> SingleOutputStreamOperator<OUT> orderedWait(
            DataStream<IN> in,
            AsyncFunction<IN, OUT> func,
            long timeout,
            TimeUnit timeUnit,
            int capacity) {
        return addOperator(in, func, timeUnit.toMillis(timeout), capacity, OutputMode.ORDERED);
    }

FlatMapFunction<T, O>

@Public
@FunctionalInterface
public interface FlatMapFunction<T, O> extends Function, Serializable {    
    void flatMap(T value, Collector<O> out) throws Exception;
}

FlatMapFunction<String, Tuple2<String, Integer>>() {
            private static final long serialVersionUID = -938116068682344455L;

            @Override
            public void flatMap(String value, Collector<Tuple2<String, Integer>> out) throws Exception {
                out.collect(new Tuple2<>(value, 1));
            }
}