为什么最终订户从未执行过？

Question

运行以下代码时，永远不会执行最终订阅者。为什么？ 我正在使用rxJava 2.1.0;我怀疑有一些猴子业务与线程，但努力想出这个。

我的实际目标是将具有相同id值字段的所有Struct实例组合（减少）到单个Reduced实例中，然后将其向下泵送到管道中。

   @Test
   public void experiment2() throws InterruptedException {

      PublishSubject<Struct> publishSubject = PublishSubject.create();

      publishSubject.buffer(3000, TimeUnit.MILLISECONDS, 10000)
              .flatMap(Observable::fromIterable)
              .groupBy(Struct::getId)
              .flatMap((GroupedObservable<String, Struct> t) -> {
                  return t.reduce(Optional.<Reduced>empty(), (Optional<Reduced> accumulator, Struct str) -> {
                     if (accumulator.isPresent()) {
                        accumulator.get().all.add(str.patternId);
                        return accumulator;
                     } else {
                        Reduced fresh = new Reduced();
                        fresh.all.add(str.patternId);
                        return Optional.of(fresh);
                     }
                  }).toObservable();
              })
              .filter(Optional::isPresent)
              .map(Optional::get)
              .subscribe((Reduced t) -> {
                 //WHY IS THIS NEVER REACHED???
                 System.out.println(t);
              });

      publishSubject.onNext(new Struct("sig1", "A"));
      publishSubject.onNext(new Struct("sig1", "B"));

      Thread.sleep(60000L);
   }

   public static class Reduced {
      private final Set<String> all = ConcurrentHashMap.newKeySet();

      @Override
      public String toString() {
         return all.toString();
      }
   }

   public static class Struct {
      private final String id;
      private final String patternId;

      public Struct(String id, String patternId) {
         this.id = id;
         this.patternId = patternId;
      }

      public String getId() {
         return id;
      }

      public String getPatternId() {
         return patternId;
      }
   }