@Override
    public void transition(ServiceComponentHostImpl impl,
        ServiceComponentHostEvent event) {
      // TODO Audit logs
      // FIXME handle restartOp event
      impl.updateLastOpInfo(event.getType(), event.getOpTimestamp());
      if (event.getType() ==
          ServiceComponentHostEventType.HOST_SVCCOMP_INSTALL) {
        ServiceComponentHostInstallEvent e =
            (ServiceComponentHostInstallEvent) event;
        if (LOG.isDebugEnabled()) {
          LOG.debug("Updating live stack version during INSTALL event, new stack version={}", e.getStackId());
        }
      }
    }
The {@link AlertDefinitionCommandTransition} is used to capture the
transition from {@link State#INSTALLING} to {@link State#INSTALLED} so that
the host affected will have new {@link AlertDefinitionCommand}s pushed to
it.
ambari-server/src/main/java/org/apache/ambari/server/state/svccomphost/ServiceComponentHostImpl.java