[concurrency-interest] CompletableFuture.get() swallows thread interrupt flag on Java 11

Jens Wilke jw_list at headissue.com
Wed Oct 14 23:33:19 EDT 2020


Hello everyone,

finally I am using more of the Java 8 concurrency code (yay!) and found 
something strange.

Here is the test code:

     Executor executor = Executors.newCachedThreadPool();
     Thread t = new Thread(() -> {
       while (!Thread.interrupted()) {
         CompletableFuture<Void> future = new CompletableFuture<>();
         executor.execute(() -> future.complete(null));
         try {
           future.get();
         } catch (InterruptedException e) {
           return;
         } catch (ExecutionException e) {
           e.printStackTrace();
         }
       }
     });
     t.start();
     Thread.sleep(1000);
     t.interrupt();
     t.join();

This is supposed to terminate after 1s.

Java version which does not terminate:
openjdk version "11.0.8" 2020-07-14
OpenJDK Runtime Environment (build 11.0.8+10-post-Ubuntu-0ubuntu120.04)
OpenJDK 64-Bit Server VM (build 11.0.8+10-post-Ubuntu-0ubuntu120.04, 
mixed mode, sharing)

Java version which does terminate:
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)

Debugging into the CompletableFuture.get() in Java 11 I can find a code 
path that resets the interrupt flag but neither restores it or throws 
the InterruptedException.

Can "someone" give that a closer look?

Warm regards,

Jens


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