private void logConfigChangeActions(ConfigChangeActions actions, DeployLogger logger) {
        RestartActions restartActions = actions.getRestartActions();
        if ( ! restartActions.isEmpty()) {
            if (configserverConfig().hostedVespa())
                logger.log(Level.INFO, "Orchestrated service restart triggered due to change(s) from active to new application:\n" +
                                       restartActions.format());
            else
                logger.log(Level.WARNING, "Change(s) between active and new application that require restart:\n" +
                                          restartActions.format());
        }
        RefeedActions refeedActions = actions.getRefeedActions();
        if ( ! refeedActions.isEmpty()) {
            logger.logApplicationPackage(Level.WARNING,
                                         "Change(s) between active and new application that may require re-feed:\n" +
                                         refeedActions.format());
        }
        ReindexActions reindexActions = actions.getReindexActions();
        if ( ! reindexActions.isEmpty()) {
            if (configserverConfig().hostedVespa())
                logger.log(Level.INFO, "Re-indexing triggered due to change(s) from active to new application:\n" +
                                       reindexActions.format());
            else
                logger.log(Level.WARNING,
                           "Change(s) between active and new application that may require re-index:\n" +
                           reindexActions.format());
        }
    }
Gets the active Session for the given application id.

@return the active session, or null if there is no active session for the given application id.
configserver/src/main/java/com/yahoo/vespa/config/server/ApplicationRepository.java