@Override
        public void execute(final Vertex vertex, final Messenger messenger, final Memory memory) {
            try {
                Thread.sleep(1);
            } catch (Exception e) {
                throw new IllegalStateException(e.getMessage(), e);
            }
            if (!this.announced) {
                memory.add("workerCount", 1l);
                this.announced = true;
            }
        }
Javadoc for {@code ConcurrentSkipListSet} includes this little note: "Beware that, unlike in most
collections, the size method is not a constant-time operation." Doing a traversal of elements will yield
the correct count. Java 11 upgrade seemed to force this failure consistently.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphComputerTest.java