@Override
    public void restart(HostFilter filter) {
        provisioner.get().restart(session.getApplicationId(), filter);
    }
Request a restart of services of this application on hosts matching the filter.
This is sometimes needed after activation, but can also be requested without
doing prepare and activate in the same session.
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/Deployment.java