Java 8 CompletableFuture,Stream和Timeouts [英] Java 8 CompletableFuture , Stream and Timeouts
问题描述
我正在尝试使用 CompletableFuture
和流
同时处理一些数据到目前为止我有:
i'm trying to process some amount of data concurrently using CompletableFuture
and Stream
So far i have:
public static void main(String[] args) throws InterruptedException, ExecutionException {
System.out.println("start");
List<String> collect = Stream.of("1", "2", "3", "4", "5",
"6", "7")
.map(x -> CompletableFuture.supplyAsync(getStringSupplier(x)))
.collect(Collectors.toList())
.stream()
.map(CompletableFuture::join)
.collect(Collectors.toList());
System.out.println("stop out!");
}
public static Supplier<String> getStringSupplier(String text) {
return () -> {
System.out.println("start " + text);
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("stop " + text);
return "asd" + text;
};
}
输出正常:
start
start 1
start 4
start 3
start 2
start 5
start 6
开始7
止损4
止损1
止损5
止损2
止损6
止损3
止损7
止损out!
但是现在我想为该工作添加超时。让我们说它应该在1 SECOND之后取消。并将null或其他值返回 collect
列表。 (我希望有一些值表明原因)。
However right now i want to add timeout to that job. Lets say it should be canceled after 1 SECOND. And return null or some other value to collect
list. (I would prefer some value indicating cause).
我如何实现这一目标?
How can i achieve that ?
提前感谢您的帮助。
推荐答案
我找到了这样做的方式:
I have found the way of doing that:
private static final ScheduledExecutorService scheduler =
Executors.newScheduledThreadPool(
1,
new ThreadFactoryBuilder()
.setDaemon(true)
.setNameFormat("failAfter-%d")
.build());
public static void main(String[] args) throws InterruptedException, ExecutionException {
System.out.println("start");
final CompletableFuture<Object> oneSecondTimeout = failAfter(Duration.ofSeconds(1))
.exceptionally(xxx -> "timeout exception");
List<Object> collect = Stream.of("1", "2", "3", "4", "5", "6", "7")
.map(x -> CompletableFuture.anyOf(createTaskSupplier(x)
, oneSecondTimeout))
.collect(Collectors.toList())
.stream()
.map(CompletableFuture::join)
.collect(Collectors.toList());
System.out.println("stop out!");
System.out.println(collect);
}
public static CompletableFuture<String> createTaskSupplier(String x) {
return CompletableFuture.supplyAsync(getStringSupplier(x))
.exceptionally(xx -> "PROCESSING ERROR : " + xx.getMessage());
}
public static Supplier<String> getStringSupplier(String text) {
return () -> {
System.out.println("start " + text);
try {
TimeUnit.MILLISECONDS.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
if (text.equals("1")) {
throw new RuntimeException("LOGIC ERROR");
}
try {
if (text.equals("7"))
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("stop " + text);
return "result " + text;
};
}
public static <T> CompletableFuture<T> failAfter(Duration duration) {
final CompletableFuture<T> promise = new CompletableFuture<>();
scheduler.schedule(() -> {
final TimeoutException ex = new TimeoutException("Timeout after " + duration);
return promise.completeExceptionally(ex);
}, duration.toMillis(), MILLISECONDS);
return promise;
}
它返回:
start
start 1
start 3
start 4
start 2
start 5
start 6
start 7
stop 6
stop 4
stop 3
stop 5
stop 2
stop out!
[PROCESSING ERROR : java.lang.RuntimeException: LOGIC ERROR, result 2, result 3, result 4, result 5, result 6, timeout exception]`
您如何看待,您能否发现该解决方案的任何缺陷?
What do you think about that, can you spot any flaws of that solution ?
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