processor-health sample in chapter 13 blocks the I/O thread

[rafaeltuelho]

At

reactive-systems-in-java/chapter-13/processor-health/src/main/java/org/acme/Processor.java

Line 28 in f9d339e

message.ack().toCompletableFuture().join();

the I/O therad gets blocked leading to

2023-02-21 21:31:32,456 WARN  [io.ver.cor.imp.BlockedThreadChecker] (vertx-blocked-thread-checker) Thread Thread[vert.x-eventloop-thread-2,5,main] has been blocked for 345343 ms, time limit is 2000 ms: io.vertx.core.VertxException: Thread blocked
        at java.base@11.0.18/jdk.internal.misc.Unsafe.park(Native Method)
        at java.base@11.0.18/java.util.concurrent.locks.LockSupport.park(LockSupport.java:194)
        at java.base@11.0.18/java.util.concurrent.CompletableFuture$Signaller.block(CompletableFuture.java:1796)
        at java.base@11.0.18/java.util.concurrent.ForkJoinPool.managedBlock(ForkJoinPool.java:3128)
        at java.base@11.0.18/java.util.concurrent.CompletableFuture.waitingGet(CompletableFuture.java:1823)
        at java.base@11.0.18/java.util.concurrent.CompletableFuture.join(CompletableFuture.java:2043)
        at io.smallrye.context.CompletableFutureWrapper.join(CompletableFutureWrapper.java:166)
        at org.acme.Processor.process(Processor.java:30)
...

I had to refactor it to something like

  @Incoming("ticks")
  @Outgoing("processed")
  @Acknowledgment(Acknowledgment.Strategy.MANUAL)
  CompletionStage<Message<String>> process(Message<Long> message) throws Exception {
    if (count++ % 8 == 0) {
      message.nack(new Throwable("Random failure to process a record.")).toCompletableFuture().join();
      return null;
    }

    return message.ack().thenApply(s -> {
      String value = String.valueOf(message.getPayload());
      try {
        value += " consumed in pod (" + InetAddress.getLocalHost().getHostName() + ")";
      } catch (UnknownHostException e) {
        throw new RuntimeException(e);
      }

      return message.withPayload(value);
    });
  }

to make it non-blocking and get the intended behavior described in the book (page 255).