public void sync() {
        msn.sync();
        net.net().sync();
    }
<p>Synchronize with internal threads. This method will handshake with all
internal threads. This has the implicit effect of waiting for all active
callbacks. Note that this method should never be invoked from a callback
since that would make the thread wait for itself... forever. This method
is typically used to untangle during session shutdown.</p>
messagebus/src/main/java/com/yahoo/messagebus/MessageBus.java