void disconnect() {
        log.log(Level.FINE, () -> "Dummy node " + DummyVdsNode.this + ": Breaking connection.");
        if (supervisor == null) return;
        register.shutdown();
        acceptor.shutdown().join();
        supervisor.transport().shutdown().join();
        supervisor = null;
        log.log(Level.FINE, () -> "Dummy node " + DummyVdsNode.this + ": Done breaking connection.");
    }
History of received cluster states.
Any access to this list or to its members must be synchronized on the timer variable.
clustercontroller-core/src/test/java/com/yahoo/vespa/clustercontroller/core/DummyVdsNode.java