當已經運行的任務之一引發異常時，我需要取消所有計劃但尚未運行的 CompletableFuture 任務。嘗試了以下示例，但大多數情況下 main 方法不會退出（可能是由于某種類型的死鎖）。public static void main(String[] args) { ExecutorService executionService = Executors.newFixedThreadPool(5); Set< CompletableFuture<?> > tasks = new HashSet<>(); for (int i = 0; i < 1000; i++) { final int id = i; CompletableFuture<?> c = CompletableFuture .runAsync( () -> { System.out.println("Running: " + id); if ( id == 400 ) throw new RuntimeException("Exception from: " + id); }, executionService ) .whenComplete( (v, ex) -> { if ( ex != null ) { System.out.println("Shutting down."); executionService.shutdownNow(); System.out.println("shutdown."); } } ); tasks.add(c); } try{ CompletableFuture.allOf( tasks.stream().toArray(CompletableFuture[]::new) ).join(); }catch(Exception e) { System.out.println("Got async exception: " + e); }finally { System.out.println("DONE"); } }最后的打印輸出是這樣的：Running: 402Running: 400Running: 408Running: 407Running: 406Running: 405Running: 411Shutting down.Running: 410Running: 409Running: 413Running: 412shutdown.嘗試shutdownNow在單獨的線程上運行方法，但在大多數情況下，它仍然會出現相同的死鎖。知道什么可能導致這種僵局嗎？您認為在CompletableFuture拋出異常時取消所有已安排但尚未運行的s的最佳方法是什么？正在考慮迭代tasks并調用cancel每個CompletableFuture. 但我不喜歡這個的是CancellationException從join.
2 回答
藍山帝景
TA貢獻1843條經驗 獲得超7個贊
另一個僅依賴的解決方案CompletableFuture是使用“取消者”未來，這將導致所有未完成的任務在完成時被取消：
Set<CompletableFuture<?>> tasks = ConcurrentHashMap.newKeySet();
CompletableFuture<Void> canceller = new CompletableFuture<>();
for(int i = 0; i < 1000; i++) {
if (canceller.isDone()) {
System.out.println("Canceller invoked, not creating other futures.");
break;
}
//LockSupport.parkNanos(10);
final int id = i;
CompletableFuture<?> c = CompletableFuture
.runAsync(() -> {
//LockSupport.parkNanos(1000);
System.out.println("Running: " + id);
if(id == 400) throw new RuntimeException("Exception from: " + id);
}, executionService);
c.whenComplete((v, ex) -> {
if(ex != null) {
canceller.complete(null);
}
});
tasks.add(c);
}
canceller.thenRun(() -> {
System.out.println("Cancelling all tasks.");
tasks.forEach(t -> t.cancel(false));
System.out.println("Finished cancelling tasks.");
});
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