void checkTimeout(String step) {
            TimeoutBudget timeoutBudget = params.getTimeoutBudget();
            if (! timeoutBudget.hasTimeLeft(step)) {
                String used = timeoutBudget.timesUsed();
                throw new UncheckedTimeoutException("prepare timed out " + used + " after " + step +
                                                    " step (timeout " + timeoutBudget.timeout() + "): " + applicationId);
            }
        }
The version of Vespa to build first when there are several config models, empty if latest version should be built first
configserver/src/main/java/com/yahoo/vespa/config/server/session/SessionPreparer.java