@Override
    public void prepare() {
        if (prepared) return;

        try (ActionTimer timer = applicationRepository.timerFor(params.get().getApplicationId(), ConfigServerMetrics.DEPLOYMENT_PREPARE_MILLIS.baseName())) {
            this.configChangeActions = sessionRepository().prepareLocalSession(session, deployLogger, params.get(), clock.instant());
            this.prepared = true;
        } catch (Exception e) {
            log.log(Level.FINE, "Preparing session " + session.getSessionId() + " failed, deleting it");
            deleteSession();
            throw e;
        }
    }
Prepares this. This does nothing if this is already prepared
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/Deployment.java